Powertrain, generic · Transmission

P08AD Neutral Position Sensor B Circuit/Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

A neutral position sensor tells the engine module whether a manual gearbox is in neutral, which start-stop, remote start and rev matching rely on. Sensor B is a second sensor or channel next to sensor A (P086A ff). P08AD flags an open or otherwise faulty sensor B circuit. No manufacturer documents this code publicly; Audi (sender G701) and GM (Corvette LT5) are only known to use the A codes. A GM patent shows why a B channel exists: two Hall sensors on the shift shaft give a PWM signal, and in neutral both must read the same. CARB 1968.2 (e)(15) requires circuit monitoring of such inputs. Expected effect: start-stop stays off; MIL status depends on the maker.

Likely causes

Wire to the sensor broken or stretched by shift shaft movement
Connector at the gearbox loose or corroded
Sensor B open internally

Symptoms

  • Start-stop no longer switches the engine off
  • Start system warning in the cluster
  • Driving normally unaffected

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

P08AEP08AFP08B0P08B1P086A

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