Network, generic (extended)

U3031 Ignition Output Off

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U3031 relates to an output whose task is to announce the off state, for example a discrete line that tells other units they may shut down, or the off branch of a power-mode output. Shutdown in many vehicles hinges on such a signal: in Ford's patent US5945745A, modules work normally while an ignition signal is present and fall back to a sleep mode with minimal current draw once it disappears, and GM's 2012 pickups allow the BCM to sleep only when none of its outputs is commanded. If the generating module finds this off output in the wrong state, it records U3031. Stuck in the not-off state, receivers stay awake and drain the battery; signalling off while driving could shut functions down on the move. No manufacturer documents U3031 publicly, so where this output sits has to be taken from the wiring diagram of the vehicle.

Likely causes

Faulty output stage in the module that generates the off signal
Off-signal wire open or shorted to ground or voltage
Corroded or loose pin at the sending or receiving module
Module software setting the off output at the wrong moment

Symptoms

  • Battery drained because modules do not go to sleep
  • Functions switching off unexpectedly with the vehicle on

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€30–700
Time0.5–3 h

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

Parts involved

ignition outputoutput wiring

Related codes

U3011U3032U302CU302DU300A

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