P27B4Internal Control Module Transmission Gear Direction Control Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- P27B4 concerns the direction in which the vehicle actually moves compared with the selected gear. GM's 2024 heavy-duty TCM tables compare the direction reported by the output speed sensor with the direction implied by solenoid and pressure switch states; disagreement for one second sets the code with MIL on the first trip. Ford's 2024 summary splits it into unintended launch (UDS P073D_48) and wrong driving direction (P073F_48), listed as non-MIL on eight- and ten-speed automatics. Despite that listing, Ford bulletins report a MIL and point to software: TSB 20-2074 for 2020 Super Duty trucks with 6.2 or 7.3 L petrol engines and the 10R140, TSB 20-2336 for the 6.7 L diesel, and TSB 26-2096 for the 2022 F-150 Lightning, where the wrench light comes from the SOBDMC.
- What you may notice
- MIL or wrench light
- Forced idle or reduced power
- Gear engagement blocked until restart
- Likely causes
- LikelyModule software strategy (Ford reprograms PCM or SOBDMC)
- PossibleFaulty direction information from the output speed sensor
- RareSolenoid or pressure switch reporting a state that does not match the gear
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €0 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.