Powertrain, generic · Transmission

P091B Gear Shift Position Circuit B Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

Likely causes

Worn or drifting shift position sensor, channels A and B disagree
Bent sensor bracket or displaced magnet on the shift rail
Gear positions not relearned after actuator or module replacement
Increased contact resistance in the sensor circuit

Symptoms

  • Transmission warning light on
  • Harsh or aborted gear changes
  • Fallback mode with fewer available gears

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,500
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

gear shift position sensor bwiring harnesstcm

Related codes

P091AP091CP091DP0915P095B

References: law.cornell.edu, patents.google.com, patents.google.com.