P27B5Internal Control Module Transmission Gear Ratio Control Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- P27B5 sets when the supervision software doubts the ratio the transmission is running. Ford describes two triggers in its 2024 summary for the eight- and ten-speed automatics: protection against overspeeding a driveline element (UDS P0701_B1) and a plausibility test of the shaft speed ratio (P0701_64), both non-MIL; the 2020–2023 edition likewise keeps it without MIL on electronically shifted models. Detection takes less than a second. Ford TSB 20-2336 covers 2020 Super Duty trucks with the 6.7 L diesel built up to 19 August 2020, where P27B5 could come with a MIL, other codes and a forced idle; PCM reprogramming was the remedy. Genuine clutch slip or a speed sensor fault can create the same mismatch, so incorrect-ratio codes such as P0730 and sensor codes need checking too.
- What you may notice
- Warning lamp or wrench light
- Forced idle or torque reduction
- Transmission held in a fixed gear
- Likely causes
- LikelyPCM/TCM software strategy (Ford TSB 20-2336)
- PossibleImplausible input, intermediate or output shaft speed signal
- RareReal slip of a clutch producing an unexpected ratio
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €0 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.