Powertrain, generic · Transmission

P081B Starter Disable Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

The starter disable line carries the signal 'park or neutral – start allowed' from the transmission module, or its built-in range switch, to the body or engine module, which only then releases the starter. On Saab's 2010 9-5 automatic the line is open in a drive range (0 V at the body module) and closed in P or N (12 V). P081B means the start release line stays at positive, so the 'P/N' level is present in a drive range. Saab's 2012 9-3 checks it only outside P and N, with 9–18 V and not in limp mode. A short to positive could in principle allow a start in gear; the diagnosis catches it, and Saab names as the effect that the engine may not start because the release is refused.

Likely causes

P/N line shorted to positive (chafed against a supply wire)
Moisture or corrosion in the connector
Transmission module output stage faulty

Symptoms

  • Engine does not start or starts unreliably
  • Start release in the wrong range possible (safety risk)
  • No check engine lamp

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–1,200
Time1–3 h

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

Parts involved

starter disable circuittransmission control modulebody control module

Related codes

P0817P081AP081DP0850P0617

References: saabwisonline.com, saabwisonline.com, law.cornell.edu.