P0135 Code on the 2023 Honda Ridgeline
Your 2023 Honda Ridgeline is powered by the proven J35Y6 3.5-liter V6 producing 280 horsepower, and the P0135 trouble code indicates the heater circuit in the Bank 1, Sensor 1 oxygen sensor has malfunctioned. This upstream sensor monitors exhaust gas oxygen content on the rear bank of the V6 before it reaches the catalytic converter. The built-in heating element is designed to bring the sensor to operating temperature within seconds of a cold start, enabling closed-loop fuel control almost immediately.
How the Heater Circuit Works
The ECM supplies battery voltage to the heater element through a fused relay circuit and controls the ground side to regulate heater operation. When the ECM detects that the sensor is not reaching its target temperature within a calibrated time window, or if the heater circuit draws abnormal current, it stores the P0135 code and illuminates the check engine light. On the 2023 Ridgeline, the ECM monitors both current draw and temperature response to detect failures precisely.
Investigating the Root Cause
- Internal heater element failure (High Likelihood): This is the number one cause of P0135 across all vehicles, and the Ridgeline is no exception. The resistive heating coil inside the Denso OEM sensor eventually burns out from repeated thermal cycling. The 2023 model is still relatively new, so this points toward a possible manufacturing defect or premature failure if the truck has low mileage.
- Wiring harness heat damage (Medium Likelihood): The V6 exhaust manifolds generate substantial heat, and the sensor wiring runs through a harsh environment. On the Ridgeline, the rear bank wiring passes close to the exhaust crossover pipe where temperatures are highest.
- Blown fuse or relay issue (Medium Likelihood): The underhood fuse box contains the O2 heater fuse. A power surge or short can blow this fuse, cutting power to the heater circuit on both banks. Check if a P0155 code accompanies P0135, which would point to a shared power supply issue.
- ECM driver circuit fault (Low Likelihood): The ECM's internal transistor that controls the heater ground can fail. This is uncommon on Honda's ECMs but not impossible. Diagnosis requires checking for proper ground switching with a lab scope or advanced scan tool.
Step-by-Step Diagnosis
Check the Easy Things First
Pull the O2 heater fuse from the underhood fuse box. Test it with a multimeter. If it is blown, replace it, clear codes, and monitor. On a 2023 model that may still be under Honda's 3-year/36,000-mile warranty, check with your dealer before performing repairs yourself, as the powertrain emissions warranty covers O2 sensors for 8 years or 80,000 miles under federal emissions regulations.
Inspect Sensor and Wiring
The Bank 1 upstream sensor on the Ridgeline V6 is on the rear exhaust manifold. Working from underneath provides the best access. Examine the four-wire connector for signs of heat damage, corrosion, or moisture intrusion. The 2023 Ridgeline has improved connector sealing over earlier generations, but damage is still possible from road debris.
Test Heater Resistance
Disconnect the sensor and measure heater resistance. A functional Denso sensor should read between 2 and 14 ohms. An open circuit or significantly high resistance confirms heater element failure. With the sensor still disconnected, verify battery voltage at the harness-side power wire with the ignition on.
Warranty and Cost Considerations
Since the 2023 Ridgeline is still within Honda's federal emissions warranty period (8 years/80,000 miles for emissions components), the O2 sensor replacement may be covered at no cost to you. Contact your Honda dealer first. If paying out of pocket, an OEM Denso sensor costs $100 to $180, and shop labor runs $120 to $200 for this location. Total out-of-pocket repair is $220 to $380. DIY saves the labor cost but requires working under the truck.
Consequences of Delaying Repair
While the P0135 code will not affect your Ridgeline's driveability once the engine warms up, the extended open-loop operation during cold starts wastes fuel and increases hydrocarbon emissions. On a truck that might sit overnight in cold temperatures, the warm-up penalty adds up. Additionally, an illuminated check engine light masks other codes that could indicate more serious problems.