P279DFour Wheel Drive (4WD) Range Signal Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- 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.
- What you may notice
- Check engine lamp
- 4WD range indicator wrong, flashing or unavailable
- Range change between high and low refused
- Likely causes
- LikelyOpen circuit or bad connector on the range switch or sensor
- PossibleRange message from the transfer case module corrupted or out of sequence
- PossibleFaulty transfer case control module or range sensor
- RareSoftware mismatch between the modules after a replacement
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.