P0135 on the 2020 Ford Ranger
The 2020 Ford Ranger is powered by the 2.3-liter EcoBoost turbocharged four-cylinder engine producing 270 horsepower and 310 lb-ft of torque. A P0135 code means the upstream O2 sensor heater circuit has malfunctioned. Since this is an inline-four, Bank 1 Sensor 1 is the only upstream O2 sensor, located between the exhaust manifold and the turbocharger on this compact turbocharged powertrain.
Midsize Truck, Full-Size Demands
The Ranger is Ford's midsize truck, used for everything from commuting to towing to light off-road duty. The 2.3L EcoBoost handles towing up to 7,500 pounds, generating significant exhaust heat under load. The upstream O2 sensor sits in one of the hottest zones of the exhaust system, right next to the turbo. At four to five years old, the heater element has endured years of demanding thermal cycles.
Causes
- Heater element burnout (High Likelihood): The Motorcraft sensor heater coil can fail from thermal fatigue after four to five years of service in the turbo-adjacent location. Rangers used for towing generate higher exhaust temperatures that accelerate heater wear. This is the most common P0135 cause.
- Wiring damage from road or trail use (Medium Likelihood): The Ranger sees varied driving conditions. Road debris, trail obstacles, and underbody impacts can damage the sensor wiring. The harness runs from the turbo area along the frame rail, where it is exposed to environmental hazards.
- Blown heater fuse (Medium Likelihood): Check the power distribution box under the hood. A blown fuse is the quickest diagnostic step and the cheapest potential fix.
- Connector corrosion (Low-Medium Likelihood): Four to five years of exposure to moisture and road salt can corrode the sensor connector pins. Inspect for green oxidation and moisture damage.
Diagnosis
Warranty Status
The 2020 Ranger is within the 8-year/80,000-mile federal emissions warranty through 2028. Verify your mileage is under 80,000 and contact your Ford dealer for a free repair.
Diagnostic Steps
Check the heater fuse first. The Ranger's body-on-frame design provides good underbody access for sensor inspection. Locate the upstream sensor near the turbocharger on the exhaust manifold. Inspect the wiring harness for damage along its route. Disconnect the sensor and test heater resistance: 3 to 15 ohms normal for Motorcraft sensors.
Turbo Access
The 2.3L EcoBoost turbo is mounted near the exhaust manifold. The upstream O2 sensor is accessible but requires working around the turbo inlet and outlet piping. From above, remove the engine cover for better visibility. From underneath, the Ranger's ground clearance gives adequate working room.
Repair Costs
Under warranty: free. Out of pocket: Motorcraft sensor $65 to $130, shop labor $100 to $170. Total: $165 to $300. DIY is feasible on the Ranger with a 22mm O2 sensor socket and some patience navigating the turbo area. Budget 45 minutes for the job.
Ranger Owner Advice
The Ranger's 2.3L EcoBoost achieves up to 26 mpg highway, good for a truck. A failed O2 sensor heater wastes fuel during every cold start, chipping away at the Ranger's efficiency advantage over full-size trucks. For Rangers that tow, the rich warm-up condition stresses the catalytic converter under the very conditions where exhaust temperatures are highest. Fix P0135 promptly to protect the turbo engine and catalytic converter.