P27F0Transmission Range Control B Position Sensor/Switch Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P27F0 checks whether mode valve B really moves. In GM's 2020 table for the T87A 10-speed RWD transmission, the TCM expects the valve B sensor to follow commands to park, reverse, neutral high or low, neutral shift and drive within a delay; if the final state is not reached under adequate line pressure, the Type A code sets. The electrical sensor codes P27EF, P27F1 and P27F2 must be clear for the test to run. In GM bulletin 21-NA-169, aimed at 9T45/50/60 automatics with under 19,000 km, P27F0 sits beside P27EC in the group where the valve body is replaced if the fluid looks healthy; dark, burnt fluid means the clutches need inspection too. Drivers notice delayed or refused range changes.
- What you may notice
- Delay or refusal when selecting neutral, drive or reverse
- MIL on, transmission may enter a protective mode
- Likely causes
- LikelyMode valve B sticking in the valve body
- PossibleInsufficient line pressure to move the valve
- RarePosition sensor B reporting late or wrong state
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €300 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.