Powertrain, generic · Transmission

P08AF Neutral Position Sensor B Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

The signal of neutral position sensor B, the second neutral sensor or channel of a manual gearbox, has fallen below its lower electrical limit. Typical reasons are a signal wire shorted to ground, a missing sensor supply or a sensor without output. No manufacturer documents P08AF publicly; the A-sensor codes are documented by Audi (sender G701, three-wire Hall sensor) and by GM on the LT5 Corvette. A GM patent describes the sensor as two Hall elements on the shift shaft feeding a PWM signal to the engine module. CARB 1968.2 (e)(15) requires low/high circuit monitoring of such inputs. High is P08B0, the A-sensor equivalent P086C. Start-stop is usually blocked; the MIL status is left to the manufacturer.

Likely causes

Signal wire chafed and shorted to ground
Sensor supply open
Sensor B without output
Water or corrosion in the connector at the gearbox

Symptoms

  • Start-stop no longer works
  • Start system warning in the cluster
  • Fault stored without driving complaint

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–350
Time0.5–2 h

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

Parts involved

neutral position sensor bwiring harnessengine control module

Related codes

P08ADP08AEP08B0P08B1P086C

References: law.cornell.edu, patents.google.com, static.nhtsa.gov.