P279CTransfer Case Gear Neutral Incorrect Ratio
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P279C applies when neutral is commanded on the transfer case, as is done for flat towing, but the shafts still turn with a fixed ratio that matches high or low range. The transfer case therefore still transmits drive. GM's 2019 ECM tables (LCV section) use the same output-speed ratio as for the other two range tests, but allow more time before deciding: the failure must last 10.5 seconds within a 15-second window. Enable conditions again require output shaft speed above 500 rpm, engine torque and pedal input and no PTO use; the fault is Type A. For towing this matters: a vehicle believed to be in neutral can drive the transmission and damage it. Range motor problems, a sticking shift sleeve and incorrect position feedback are the main suspects; P279A and P279B are the high and low counterparts.
- What you may notice
- Vehicle still drives or creeps with neutral selected
- Neutral request rejected, 4WD warning on
- MIL on
- Likely causes
- LikelyRange shift motor not reaching neutral
- PossibleSticking shift sleeve keeping a range engaged
- PossibleWrong position feedback from the range sensor
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.