P0135 on the 2018 Ford F-150
The 2018 Ford F-150 offers the second-generation 3.5L EcoBoost twin-turbo V6, the 5.0L Coyote V8, the 2.7L EcoBoost V6, and the 3.3L Ti-VCT V6. At six to seven years old, a P0135 code on any of these engines points to a heater circuit malfunction in the upstream O2 sensor on Bank 1. The sensor's internal heater element may be reaching the end of its service life.
Age and Mileage Considerations
Many 2018 F-150s have accumulated 80,000 to 150,000 miles, which is well within the range where O2 sensor heater failures become common. These trucks are workhorses that tow, haul, and commute in all weather conditions. The combination of mileage, thermal cycling, and environmental exposure makes heater element burnout the most likely cause at this age.
Root Causes
- Heater element burnout from age (High Likelihood): Six to seven years and potentially high mileage put the Motorcraft sensor's heater coil at the top of its wear curve. Each cold start cycles the heater, and the thin resistive wire eventually fractures from metal fatigue. Trucks used for towing accumulate additional thermal stress.
- Corrosion and environmental damage (Medium Likelihood): Years of road salt, mud, water, and debris have taken their toll on the sensor wiring and connector. The F-150's underbody is exposed to harsh conditions. Corroded connector pins create resistance that the PCM interprets as a heater malfunction.
- Blown heater fuse (Medium Likelihood): The power distribution box under the hood houses the O2 heater fuse. A wiring short from damaged insulation can blow the fuse. Always check the fuse first.
- Wiring abrasion along the frame (Low-Medium Likelihood): After years of vibration and road exposure, the sensor wiring running along the frame rail can develop abrasion points. The insulation wears through where the harness contacts brackets or body components, creating shorts or opens.
Diagnosis
Warranty Status
The 2018 F-150 may still be within the 8-year/80,000-mile federal emissions warranty, depending on the in-service date and mileage. Check with your Ford dealer. If the truck has over 80,000 miles, this will be an out-of-pocket repair.
Systematic Checks
Start with the fuse in the power distribution box. Then raise the truck and inspect the Bank 1 sensor wiring from the exhaust manifold along the frame rail to the connector. Look for abrasion points, corroded connections, and damaged insulation. On the 5.0L V8, the passenger-side sensor is accessible along the exhaust manifold. On EcoBoost engines, access near the turbo is more challenging.
Resistance Test
Disconnect and test heater resistance: 3 to 15 ohms is normal for Motorcraft sensors. Open circuit means the heater is dead. After six years, if resistance is borderline high, the sensor should be replaced preventively.
Sensor Removal on Aged Trucks
The sensor threads will be seized after six years in the exhaust manifold. Soak generously with PB Blaster or similar penetrating oil. Let it sit for at least an hour. Warming the engine briefly can help expand the bung. Use a proper 22mm O2 sensor socket and apply steady force to avoid rounding the hex.
Repair Costs
Motorcraft sensor: $60 to $140 depending on engine. Aftermarket options: $25 to $55. Shop labor: $100 to $180. Total professional repair: $160 to $320. DIY is practical on the 5.0L from underneath the truck. EcoBoost sensor access near the turbo is more challenging. Budget 30 to 60 minutes plus time for seized thread removal.
Worth Fixing
The 2018 F-150 holds its value well, and many owners keep these trucks for a decade or more. A $160 sensor replacement protects the catalytic converters ($600 to $1,800 per side) and restores fuel efficiency. On a truck that uses 15 to 22 mpg normally, even a 5 percent fuel economy improvement from fixing the heater saves money quickly.