Powertrain, generic · Transmission

P09A3 Gate Select Position Circuit B Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Plausibility fault of gate select circuit B: the signal is electrically valid but does not match what the module expects. That could be the reading of circuit A, the learned gate positions, or the target gate the module has commanded, as in the Aisin AI select control that compares actual and target gate. Which comparison applies depends on whether B is a redundant track or a separate sensor, and no manufacturer publishes that or uses this code in citable material. CARB requires rationality checks on such inputs. P09A2, P09A4 and P09A5 are electrical faults of B, P0905 and P09A7 the same check on circuits A and C. A fallback mode with limited shifting is likely.

Likely causes

Worn or drifting select sensor, signal B no longer agrees with the reference
Gate positions not relearned after actuator, clutch or module replacement
Contact resistance at connector pins distorting signal B
Sluggish or worn select mechanism so the measured gate lags the commanded one

Symptoms

  • Check engine or transmission warning light on
  • Wrong gate selected or gears refused
  • Slow, jerky shifting in fallback mode

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,500
Time0.5–4 h

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

Parts involved

gate select position sensor bwiring harnesstcm

Related codes

P09A2P09A4P09A5P0905P09A7P0909

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