Cracking the P0135 Code in Your 2020 Dodge Challenger
Your 2020 Dodge Challenger has alerted you with a check engine light and diagnostic code P0135, signaling a heater circuit malfunction in the Bank 1, Sensor 1 oxygen sensor. The Challenger, Dodge's iconic two-door muscle car that revived the legendary nameplate in 2008, offers a diverse powertrain lineup for 2020. Options span from the efficient 3.6L Pentastar V6 producing 303 horsepower, through the classic 5.7L HEMI V8 (375 hp), the aggressive 6.4L HEMI V8 (485 hp in Scat Pack and 392 models), to the supercharged monsters: 6.2L HEMI producing 717 hp in Hellcat or up to 797 hp in Hellcat Redeye trim.
Understanding Bank 1 requires knowing your Challenger's V-engine architecture. On all Dodge V6 and V8 configurations, Bank 1 refers to the cylinder bank containing cylinder number one—consistently the passenger side. Sensor 1 designates the upstream oxygen sensor positioned before the catalytic converter in the exhaust manifold or header pipe. This sensor's integrated heater element rapidly warms the sensor tip to approximately 600-700°F within 20-30 seconds of startup, enabling immediate transition to closed-loop fuel control for optimal performance and emissions compliance.
The 2020 Challenger continues on the proven LC platform that debuted in 2008 with evolutionary refinements. Exhaust system architecture varies dramatically by powertrain: V6 models utilize a single catalytic converter with two upstream O2 sensors (one per bank), while HEMI V8 models feature true dual exhaust with independent catalytic converters and O2 sensors for each bank. This means V8 Challengers have twice the sensors that could potentially fail, though P0135 specifically addresses only Bank 1. High-output variants like Hellcat models employ high-flow exhaust systems optimized for extreme performance, creating particularly demanding thermal environments where exhaust temperatures can spike beyond 1700°F under full throttle.
Detecting the Symptom Pattern
The P0135 code manifests through several observable symptoms that extend beyond the illuminated check engine light on your Challenger's instrument cluster. The most prominent indicator appears during cold starts, particularly noticeable on mornings when ambient temperatures fall below 50°F. Your Challenger's engine may exhibit slightly uneven idle characteristics during the first 60-90 seconds of operation, with tachometer readings fluctuating between 600-850 RPM for V6 and naturally aspirated V8 models, or 700-900 RPM for supercharged Hellcat variants, rather than settling immediately at the target cold idle speed. This roughness typically resolves progressively as the O2 sensor gradually reaches operating temperature through exposure to exhaust heat alone.
Fuel economy degradation provides another reliable diagnostic indicator. The EPA rates the 2020 Challenger at 19 city/30 highway for the V6, 15/24 for the 5.7L HEMI, 13/22 for the 6.4L HEMI in Scat Pack trim, and 12/21 for supercharged Hellcat models. With P0135 actively set, expect to see a 1-3 mpg decrease in mixed driving conditions. V6 owners typically averaging 24 mpg combined might experience drops to 21-23 mpg, while HEMI owners usually seeing 18-20 mpg could notice declines to 16-18 mpg. Given the Challenger's generous 18.5-gallon fuel tank and current fuel market pricing, this translates to approximately $18-35 additional cost per fill-up depending on your specific engine configuration and local fuel rates.
Performance characteristics reveal additional investigative clues for the automotive detective. During the initial 5-10 minutes following a cold start, V6 Challengers may exhibit slightly muted throttle response when accelerating from stops or merging into highway traffic. HEMI V8 models, particularly the 392 variants with their 6.4L engines, may feel noticeably less eager during warmup—the normally immediate throttle response and characteristic HEMI bark take longer to fully develop their addictive character. Hellcat models with supercharged 6.2L engines may experience delayed boost response and less aggressive power delivery until the O2 sensor reaches proper operating temperature and allows the PCM to optimize boost pressure and ignition timing. These sophisticated performance powertrains rely extensively on accurate real-time O2 sensor feedback to optimize ignition timing, fuel delivery, and boost control in supercharged applications.
Some Challenger owners report detecting a subtle sulfur or rotten egg odor emanating from the exhaust during the warmup phase, sometimes described as smelling like burning matches. This characteristic smell indicates the catalytic converter is working overtime to process slightly richer exhaust gases when the powertrain control module operates in open-loop mode without accurate sensor feedback. The odor typically dissipates once closed-loop operation resumes after the sensor self-heats through exhaust temperature, usually 5-10 minutes into your drive depending on ambient conditions and driving style.
Owners of Challengers equipped with factory active exhaust systems (available on higher-performance models) may notice the exhaust remaining in quiet mode longer than usual during warmup, as the PCM adopts conservative calibration strategies without complete sensor data. The Multi-Displacement System in 5.7L HEMI models, which deactivates four cylinders during light-load cruising to improve fuel economy, might engage less frequently or not at all during extended warmup periods, affecting both fuel efficiency and the characteristic V8 exhaust note transitions that enthusiasts appreciate.
Uncovering the Root Causes
Systematic investigation of P0135 diagnostic codes across 2020 Challenger models reveals four primary failure mechanisms, with some notable variation depending on engine displacement and performance level.
Failed Oxygen Sensor Heater Element (48% likelihood): Internal heater element failure represents the dominant cause of P0135 codes in third-generation Challengers across all engine variants. The oxygen sensor incorporates a small ceramic resistor coil designed to draw approximately 0.8-1.2 amps and generate rapid internal heating to bring the sensor to its critical operating temperature. Repeated thermal cycling from warmup and cool-down cycles—potentially dozens of cycles daily for commuter vehicles—eventually induces microscopic fractures in the ceramic element or its delicate internal electrical connections. High-performance HEMI engines, particularly the 6.4L in Scat Pack and 392 models and especially the supercharged 6.2L in Hellcat variants, generate dramatically more aggressive exhaust temperatures than the V6—peak temperatures can reach 1600-1800°F under full throttle acceleration or sustained high-load operation like drag racing. This extreme thermal environment dramatically accelerates sensor aging and shortens service life compared to more sedate driving patterns. Chrysler typically sources oxygen sensors from Bosch or NTK for Challenger applications, with manufacturer design life expectations of 80,000-120,000 miles under normal moderate driving conditions. However, enthusiastic driving patterns common in performance-oriented Challenger ownership can substantially reduce this service life to 50,000-70,000 miles. A properly functioning heater circuit measures 2-10 ohms resistance at room temperature when tested with a multimeter; infinite resistance readings clearly indicate a complete open circuit failure, while near-zero resistance (less than 1 ohm) suggests an internal short circuit that will typically blow the circuit protection fuse immediately.
Wiring Damage or Connector Corrosion (31% likelihood): The Challenger's performance-focused exhaust system routing necessarily places O2 sensor wiring in close proximity to high-temperature exhaust components throughout both the engine bay and undercarriage areas. On V6 models with transverse engine mounting orientation, both upstream sensors install directly in the exhaust manifolds with wiring routed through the congested engine valley area where heat accumulation from both cylinder banks is significant. HEMI V8 models with longitudinal engine orientation position sensors in each exhaust header pipe or manifold, with wiring harnesses running along the frame rails in unavoidably close proximity to the hot exhaust system pipes. The electrical connectors, typically located strategically near the transmission bellhousing area or along the inner fender wells, can gradually accumulate moisture intrusion over time and develop troublesome terminal corrosion, particularly in humid climates or regions with significant precipitation. Road spray containing salt and chemical de-icing agents dramatically accelerates this corrosion process, making connector-related issues substantially more prevalent in northern climates experiencing harsh winters with aggressive road treatment programs. The sensor wiring itself utilizes relatively thin 18-20 gauge conductors protected by heat-resistant insulation specifically rated for exhaust environments, but prolonged exposure to temperatures consistently exceeding 400°F can progressively degrade even this specialized protection over time. Enthusiast Challenger owners who install popular aftermarket exhaust modifications—performance headers, high-flow catalytic converters, or aggressive cat-back exhaust systems—sometimes inadvertently damage delicate O2 sensor wiring during installation procedures, creating immediate failures or degraded connections that fail progressively over subsequent weeks or months.
Blown Fuse or Relay Failure (13% likelihood): The O2 sensor heater circuits in the 2020 Challenger draw substantial electrical current, particularly in V8 models where four upstream sensors operate simultaneously during startup and warmup, and are protected by dedicated fuses located in the Integrated Power Module positioned in the engine bay near the battery. V6 configurations typically employ 15-amp mini-blade fuses for heater circuit protection, while V8 models frequently utilize 20-amp fuses to accommodate the higher total current draw from multiple sensors operating concurrently. Modern automotive fuses are highly reliable components that rarely fail spontaneously without underlying cause, but short circuits elsewhere in the heater system will blow the protective fuse as designed, preventing damage to more expensive downstream components like the PCM. The associated relay that switches battery power to the heater circuits under PCM command can develop internal contact surface degradation or coil failures over extended service, though this failure mode remains relatively uncommon in vehicles under five years old with moderate mileage. Checking fuse condition should always constitute your very first diagnostic step due to its exceptional accessibility and minimal cost investment—spending hours on complex circuit testing makes no sense if a simple $3 fuse is the actual culprit.
PCM Software Calibration or Driver Circuit Issue (8% likelihood): The powertrain control module in your 2020 Challenger represents a sophisticated embedded computer system managing hundreds of sensor inputs and actuator outputs through complex software algorithms specifically calibrated for your exact engine configuration and emissions requirements. Occasionally, the internal driver circuit that supplies switched power to individual O2 sensor heaters can fail internally due to component degradation, preventing heater operation despite having a properly functioning sensor and completely intact wiring harness. More commonly encountered are calibration errors or excessively sensitive monitoring parameters in the PCM software that might incorrectly flag P0135 when the circuit is actually functioning within acceptable parameters—essentially a false positive triggered by overly aggressive monitoring tolerances. Chrysler periodically releases software updates through their dealer network addressing various sensor monitoring parameters, driveability refinements, and emissions system optimizations discovered through field experience. If your Challenger has never received PCM software updates since original purchase, checking for available calibration updates is definitely worthwhile during your diagnostic process. Complete PCM hardware failure is exceptionally rare in modern vehicles with reasonable mileage and would typically present with multiple unrelated fault codes spanning various vehicle systems plus significant driveability issues far exceeding what P0135 alone would cause.
Systematic Diagnostic Procedures
Properly diagnosing P0135 in your 2020 Challenger requires methodical testing procedures with appropriate diagnostic tools and equipment. Essential tools include an advanced OBD-II scanner with live data streaming capability (basic inexpensive code readers that only pull codes are insufficient for proper diagnosis), a quality digital multimeter with accurate resistance and voltage measurement functions, basic hand tools including various socket and wrench sizes, and a specialized 22mm O2 sensor socket if you plan to remove the sensor for testing or replacement—standard deep sockets cannot physically clear the wiring pigtail that extends from the sensor body. Critical safety reminder: exhaust systems retain dangerous heat for extended periods, particularly in high-performance applications with large-displacement engines, so always allow the engine and complete exhaust system to cool fully before working near sensors or manifolds.
Begin diagnostic procedures by connecting your OBD-II scanner to the diagnostic port located under the driver's side dashboard and retrieving all stored diagnostic trouble codes, including both currently active codes and pending codes that haven't yet triggered the check engine light. Carefully document whether P0135 appears as an isolated single fault or is accompanied by related companion codes such as P0155 (Bank 2 Sensor 1 heater circuit malfunction, present on V8 models with dual banks), P0131 (Bank 1 Sensor 1 circuit low voltage), P0133 (Bank 1 Sensor 1 slow response time), or P0420/P0430 (catalyst system efficiency below threshold for Banks 1 and 2). Access the valuable freeze frame data that captures precise operating conditions at the exact moment P0135 first triggered: engine coolant temperature, vehicle speed, calculated engine load, and engine runtime since startup are particularly relevant diagnostic parameters. Codes that set immediately at cold engine start strongly indicate heater circuit electrical problems, while codes appearing only after several minutes of operation may suggest different underlying issues like sensor contamination or exhaust leaks.
Navigate to your scanner's live data display function and locate the O2 sensor heater command parameters for all sensors. With the ignition key in the on position but engine not yet running, the PCM should immediately command all heater circuits to active status, typically displayed as ON or 100% duty cycle in most scan tool interfaces. Simultaneously monitor the Bank 1 Sensor 1 voltage signal output on your scanner display—even a completely cold sensor should show some voltage activity, typically fluctuating irregularly between 0.1-0.9 volts as it attempts to read the rich cold-start mixture. If the heater command clearly shows active status but the sensor voltage signal remains frozen at a constant value without any fluctuation, this pattern strongly suggests a failed heater element preventing the sensor from reaching its critical operating temperature where it can generate meaningful voltage signals corresponding to exhaust oxygen content.
Perform a comprehensive visual inspection of the Bank 1 Sensor 1 physical location and associated wiring harness. For V6 Challengers with transverse engine mounting, this sensor installs in the passenger-side exhaust manifold, typically accessed from above engine with moderate difficulty due to tight clearances around various engine accessories and components. For HEMI V8 models with longitudinal engine orientation, the passenger-side upstream sensor generally offers better accessibility from underneath the vehicle with the car properly and safely supported on quality jack stands or a professional lift. Carefully trace the sensor wiring back to its electrical connector, methodically inspecting the entire visible wiring run for any signs of melted or heat-damaged insulation, chafing wear against sharp metal edges or exhaust components, or obvious physical damage from impact or misrouting. Disconnect the sensor connector by carefully pressing the release tab mechanism and separating the connector halves. Thoroughly examine both the sensor-side and vehicle-side connector terminals for corrosion (visible as green or white crusty deposits on brass terminals), pushed-back or recessed pins that don't make proper mating contact, or contamination from engine oil or moisture intrusion.
With the connector properly separated, configure your digital multimeter to resistance (ohms) measurement mode to test the heater circuit electrical characteristics. On Chrysler four-wire O2 sensors used in Challenger applications, the heater circuit typically utilizes specific pins in the connector arrangement—consult a factory wiring diagram for your exact engine configuration if uncertain about pin identification. Carefully touch your meter probe tips to the heater circuit terminals on the sensor side of the separated connector. A healthy, properly functioning heater element should measure between 2-10 ohms resistance at standard room temperature (approximately 68-72°F). An infinite resistance reading (displayed as OL or overload on most digital meters) clearly indicates a complete open circuit—the heater element has failed internally with a broken electrical connection. A near-zero resistance reading (less than 1 ohm) suggests an internal short circuit within the sensor that will cause excessive current draw and immediately blow the protective circuit fuse. Additionally test for proper insulation integrity by measuring resistance between each individual heater terminal and the sensor's metal body or threaded mounting portion. You should consistently measure infinite resistance in these tests, confirming no short-to-ground condition exists within the sensor assembly.
If the sensor tests within proper specifications, shift diagnostic focus to the vehicle wiring harness and power supply. With the connector still separated, switch your multimeter to DC voltage measurement mode. Turn the ignition key to the on position without starting the engine (some vehicle systems may require brief engine cranking to fully activate heater circuits). Carefully backprobe the vehicle harness connector using appropriate test pins or probes and measure voltage present across the heater circuit terminals. One terminal should display battery voltage (approximately 12-14 volts depending on battery state of charge) and the opposite terminal should provide a solid ground path (0-0.5 volts) when the PCM actively commands the heater circuit to on status. Complete absence of expected voltage indicates a problem somewhere in the path between the power distribution center and the sensor location: broken or severed wiring, a blown protective fuse, a failed power relay, or a PCM internal driver circuit failure.
Inspect the O2 sensor heater circuit protective fuse in the Integrated Power Module (IPM) located in the engine bay, typically positioned near the battery or on the driver-side inner fender. Your owner's manual provides detailed fuse box diagrams with individual fuse locations, amperage ratings, and circuit descriptions. Locate the fuse specifically labeled for O2 sensor heaters (labeling conventions vary but typically include abbreviations like O2, HTR, or SENSOR in the designation), remove it using the plastic fuse puller tool conveniently stored in the fuse box cover, and visually inspect the metal fuse element visible through the clear plastic fuse body. A blown fuse displays an obviously broken or melted element that's readily apparent. For additional confirmation beyond visual inspection, test the removed fuse with your multimeter's continuity or resistance function—a functional good fuse shows zero resistance (perfect continuity), while a blown fuse displays infinite resistance (complete open circuit with no continuity).
Repair Solutions and Cost Investment
For the majority of 2020 Challenger owners diagnosed with confirmed P0135 faults, replacing the Bank 1 Sensor 1 oxygen sensor resolves the issue successfully in approximately 80% of cases. Parts pricing varies somewhat by engine configuration and performance level: genuine Mopar oxygen sensors cost $145-$230 for V6 applications and $155-$245 for HEMI V8 models, with Hellcat-specific sensors occasionally commanding slight premium pricing due to their specialized high-temperature ratings. Quality aftermarket alternatives from established reputable manufacturers like Bosch, Denso, or NTK range from $90-$165 for V6 sensors and $95-$180 for HEMI applications, offering substantial cost savings with generally acceptable performance characteristics and reliability for most driving applications.
Professional installation service at a Dodge dealership typically costs $270-$440 total including both parts and skilled labor for V6 models, with labor charges running approximately $125-$210 for 1.0-1.5 hours of certified technician time depending on regional labor rate variations and local market conditions. HEMI V8 sensor replacement is generally slightly more accessible when approached from underneath the vehicle, averaging $250-$400 total cost. Independent repair shops often charge moderately less than franchised dealerships, typically around $230-$370 for V6 models and $210-$340 for V8 configurations, though service quality and diagnostic expertise levels vary significantly between independent facilities.
DIY replacement is definitely achievable for Challenger owners with moderate mechanical aptitude, basic tool familiarity, and appropriate workspace. For V6 models, top-side access through the engine bay presents moderate challenges due to tight packaging constraints but remains feasible with patience and proper tool selection. You'll need a 22mm O2 sensor socket (absolutely essential—standard sockets physically cannot fit), a 3/8-inch-drive ratchet with various extension lengths for reach and angle, and anti-seize compound specifically rated for high-temperature exhaust applications (never use standard general-purpose anti-seize on O2 sensors as certain formulations can contaminate the sensing element and cause premature failure). Allow 90-120 minutes for first-time DIY attempts on V6 models. HEMI V8 configurations generally offer easier sensor access from underneath the vehicle when properly and safely supported on quality jack stands or steel ramps, typically requiring 45-75 minutes even for first-time attempts by mechanically inclined owners. Absolutely ensure the engine and complete exhaust system are fully cool before beginning work—exhaust components can cause severe burns hours after shutdown. Procedure: disconnect the battery negative terminal for electrical safety, locate and disconnect the sensor electrical connector by pressing the release tab, use the 22mm O2 sensor socket to carefully unthread the old sensor from the exhaust manifold or header pipe (turning counterclockwise with steady pressure), inspect the threads in the manifold boss and clean with an appropriate thread chaser if you observe any damage or accumulated carbon deposits, apply a very thin coat of high-temperature anti-seize compound to the new sensor's threads while meticulously avoiding any contact with the sensor tip or ceramic sensing element, hand-thread the new sensor into position using only hand pressure initially to prevent accidental cross-threading damage, torque the sensor to manufacturer's specification of 30-35 ft-lbs using a calibrated torque wrench, carefully route the new sensor wiring away from all exhaust components and potential heat sources while ensuring no tension or stress on the wiring, reconnect the electrical connector ensuring it locks properly with an audible click, reconnect the battery negative terminal, and clear diagnostic codes with your scanner tool. Test drive through several complete cold-start warmup cycles under various driving conditions to confirm successful repair and verify P0135 does not return. Total DIY investment: $90-$245 depending on parts quality selection, plus approximately $30-50 for specialized tools if not already owned.
If comprehensive diagnostic testing definitively reveals wiring harness damage as the root cause rather than sensor internal failure, repair costs vary dramatically based on damage severity and physical extent of affected wiring. Simple connector terminal cleaning or individual terminal replacement costs approximately $75-$140 at most professional repair shops. Repairing a single damaged wire section with proper splicing techniques runs $95-$200 including skilled labor charges. Extensive harness damage requiring complete replacement of the entire O2 sensor sub-harness from the sensor location back to the main engine harness connector ranges from $240-$450 including both replacement parts and professional installation labor. Experienced DIY enthusiasts with electrical repair skills can successfully tackle wiring repairs using proper weatherproof crimp connectors, adhesive-lined heat-shrink tubing for superior environmental protection, and correct new terminals from quality component suppliers like TE Connectivity or Delphi Packard, reducing material costs to approximately $25-45 while requiring significant time investment and developing electrical skills.
A blown protective fuse represents the least expensive repair scenario at merely $3-$10 for the replacement fuse itself (OEM Mopar fuses always recommended over generic discount auto parts store variants for optimal reliability and correct amperage ratings matching original specifications). However, simply replacing a blown fuse without systematically identifying and addressing the underlying short circuit condition that caused it to blow as designed will result in immediate re-failure upon the very next ignition cycle—the new fuse will blow again instantly. PCM-related issues are relatively uncommon but represent the most expensive repair pathway when they do occur: software reflashing service at a Dodge dealership costs $120-$230 including diagnostic time and programming procedures, while complete PCM replacement (almost never actually necessary solely to address P0135) reaches $650-$1,400 including the replacement control module, mandatory vehicle-specific security programming linking the new PCM to your specific vehicle, and professional installation labor.
Proactive Prevention Strategies
Several proactive maintenance practices and driving habits can significantly extend oxygen sensor service life in your performance-oriented Challenger across all engine variants. Use exclusively the fuel octane grade specified by Dodge for your particular engine configuration: 87 octane regular unleaded for the 3.6L Pentastar V6, 89 octane mid-grade recommended (though 87 acceptable for normal driving) for the 5.7L HEMI, 91 octane premium absolutely required for the 6.4L HEMI in Scat Pack and 392 models, and 91 octane premium required for all supercharged Hellcat models to prevent destructive detonation. Consistently use top-tier detergent gasoline from major brand stations certified by AAA (including well-known brands like Chevron with Techron, Shell V-Power, ExxonMobil Synergy, BP Invigorate, Marathon, and others) to minimize combustion chamber deposits, intake valve deposits, and fuel system contamination that can negatively affect exhaust composition and oxygen sensor longevity.
Avoid unnecessary fuel additives, octane boosters, or fuel system cleaners unless specifically addressing documented performance problems with clear manufacturer or dealer recommendation. Many aftermarket fuel additives contain compounds and chemicals that can coat or contaminate delicate oxygen sensor ceramic elements, causing premature failure or false voltage readings that trigger diagnostic codes unnecessarily. Monitor engine oil consumption patterns carefully and systematically—any engine consuming noticeable oil between normal service intervals exposes oxygen sensors to silicate ash derived from oil additive packages, which progressively coats sensor elements and degrades response time and measurement accuracy. Check your engine oil level monthly using the dipstick; investigate promptly and systematically if you're adding more than one quart between Dodge's recommended 5,000-mile service intervals (or as indicated by the intelligent Oil Change Indicator system based on actual driving conditions and oil degradation monitoring).
Follow Dodge's recommended maintenance schedule with precision and consistency: oil changes strictly according to the Oil Change Indicator system recommendations (typically 4,000-6,000 miles depending on driving style severity and operating conditions), spark plug replacement at the specified 100,000-mile interval for V6 engines or dramatically shorter 30,000-mile interval for HEMI V8 engines (note the very significant and important difference in service intervals between these engine types due to different ignition system designs), and engine air filter inspection at every oil service interval with replacement as visual inspection and operating conditions warrant. Worn or fouled spark plugs cause cylinder misfires that dump unburned raw fuel directly into the exhaust stream, rapidly contaminating both oxygen sensors and expensive catalytic converters while potentially causing catalyst substrate damage requiring costly replacement of the entire catalytic converter assembly.
For enthusiast drivers regularly enjoying the Challenger's substantial performance capabilities on track days, drag strips, canyon runs, or spirited highway driving sessions, implement proper engine cool-down procedures after aggressive operation. Allow the engine to idle peacefully for 60-120 seconds after track sessions, drag racing passes, or sustained high-load driving to normalize exhaust system temperatures gradually and progressively rather than shocking sensors, catalytic converters, and exhaust components with sudden shutdown thermal transients that dramatically accelerate component aging and reduce service life.
For Challenger owners located in northern climates facing harsh winters with extensive road salt application and chemical de-icing agent use, periodically spray oxygen sensor electrical connectors with quality electrical contact cleaner and apply fresh dielectric grease generously to connector terminals to prevent corrosion and moisture intrusion that causes connection resistance and intermittent faults. Inspect connectors thoroughly during routine oil changes or any underhood maintenance activities as part of your regular inspection routine.
When Professional Diagnosis Becomes Essential
While P0135 diagnosis follows a relatively straightforward and logical troubleshooting pathway for mechanically inclined owners, several specific scenarios strongly warrant professional assistance rather than continued DIY diagnostic attempts. If you lack confidence working safely with automotive electrical diagnostic equipment or accurately interpreting digital multimeter readings and understanding their implications, the typical $110-$180 diagnostic fee charged by reputable independent repair shops or Dodge dealerships represents money very well invested compared to the risk and expense of misdiagnosing the actual root problem and replacing unnecessary components that don't address the real issue.
Professional automotive technicians maintain continuous access to Chrysler's complete factory service information systems, detailed accurate wiring diagrams showing every circuit and connection, and technical service bulletins (TSBs) that provide model-specific and even VIN-specific troubleshooting sequences, known issues, and updated repair procedures completely unavailable to the general public or accessible through generic repair manuals. If you replace the oxygen sensor based on your diagnostic conclusion but P0135 returns immediately upon clearing codes or reappears within a few hundred miles of subsequent driving, an underlying electrical issue definitely exists in the system that requires systematic professional diagnosis with dealer-level scan tools offering enhanced capabilities and specialized diagnostic equipment not available to typical DIYers.
Intermittent fault codes that appear and disappear randomly without any discernible pattern or correlation to specific operating conditions often indicate damaged wiring harnesses with intermittent short circuits, marginal electrical connector contacts that fail sporadically under vibration or temperature cycling stress, or failing relays that work intermittently depending on internal contact temperature—all challenging diagnostic scenarios that can prove extremely frustrating and time-consuming to locate and definitively confirm without substantial professional experience and specialized diagnostic equipment like digital storage oscilloscopes, circuit load testers, or thermal imaging cameras.
When P0135 appears accompanied by multiple related companion codes—particularly catalyst efficiency codes (P0420 indicating Bank 1 catalyst or P0430 indicating Bank 2 catalyst), fuel system codes (P0171 indicating system too lean or P0172 indicating system too rich), or multiple O2 sensor codes affecting different sensors in various locations—the issue almost certainly extends well beyond a simple isolated heater circuit failure in one sensor. This multi-code pattern strongly suggests broader underlying exhaust system problems like exhaust leaks affecting sensor readings, fundamental fuel delivery issues affecting overall air-fuel ratios, or PCM-related problems affecting multiple monitoring and control systems simultaneously, all requiring comprehensive professional diagnosis that systematically tests related systems and components rather than focusing narrowly on individual component replacement.
Most importantly for owners of newer vehicles still under warranty coverage, if your 2020 Challenger remains under any applicable Chrysler factory warranty coverage (3 years or 36,000 miles comprehensive bumper-to-bumper coverage, 5 years or 60,000 miles powertrain coverage protecting engine and transmission), always initiate diagnosis and repair at your authorized Dodge dealer rather than attempting independent repairs yourself or using independent repair facilities. The repair will be performed at absolutely no cost to you under warranty coverage, and critically important proper dealer documentation creates a permanent detailed service record in Chrysler's national warranty claim database that legally protects you and establishes precedent if any related issues or problems emerge after your warranty coverage period expires. Dealers maintain unique ability to check for unpublicized confidential technical service bulletins, identify factory-known issues, or access available software updates specific to your exact vehicle's VIN, production sequence date, and current PCM software calibration level that may successfully address P0135 issues through updated programming procedures rather than requiring any physical parts replacement whatsoever.