Powertrain, generic (extended)

P279D Four Wheel Drive (4WD) Range Signal Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P279D concerns the signal that tells the powertrain which transfer case range is active: 4WD high, 4WD low or neutral. Drivetrain controllers need it to apply the right ratio, torque limits and shift logic. GM documents the code for its 2008 Two-Mode Hybrid in the hybrid control module (HCP), where the range arrives as a network message: the module checks its alive rolling counter, which must increase by one each time, and a protection value that must match the primary value. Five failed samples out of eight while the ignition is in run or crank set the code, with MIL after one trip. Other designs read the range from a switch or sensor wire, so the same code can also mean an open circuit. P279E, P279F and P27A0 cover plausibility, low and high faults of this signal.

Likely causes

Open circuit or bad connector on the range switch or sensor
Range message from the transfer case module corrupted or out of sequence
Faulty transfer case control module or range sensor
Software mismatch between the modules after a replacement

Symptoms

  • Check engine lamp
  • 4WD range indicator wrong, flashing or unavailable
  • Range change between high and low refused

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–900
Time0.5–3 h

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

Parts involved

four wd range sensortransfer casewiring harness

Related codes

P279EP279FP27A0P279AP2771

References: gsi.ext.gm.com, law.cornell.edu.