P091BGear Shift Position Circuit B 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
- Plausibility fault of the shift position signal on circuit B in an automated manual gearbox. The voltage stays within its electrical limits, yet the value does not fit: it disagrees with circuit A, does not change while the shift actuator moves, or does not match the learned gear positions. No manufacturer documents this code publicly. A Nissan/Aichi patent notes that sensor mountings on shift parts can deform under vibration and falsify the reading, and an Aisin AI patent describes how the control continues when a stroke sensor is no longer trusted. CARB requires rationality checks on such inputs. P091A, P091C and P091D are the electrical faults of circuit B, P0915 the same check on circuit A. Gear changes may be limited.
- What you may notice
- Transmission warning light on
- Harsh or aborted gear changes
- Fallback mode with fewer available gears
- Likely causes
- LikelyWorn or drifting shift position sensor, channels A and B disagree
- PossibleBent sensor bracket or displaced magnet on the shift rail
- PossibleGear positions not relearned after actuator or module replacement
- RareIncreased contact resistance in the sensor circuit
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.