Powertrain, generic (extended)

P279C Transfer Case Gear Neutral Incorrect Ratio

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Range shift motor not reaching neutral
Sticking shift sleeve keeping a range engaged
Wrong position feedback from the range sensor

Symptoms

  • Vehicle still drives or creeps with neutral selected
  • Neutral request rejected, 4WD warning on
  • MIL on

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–3,000
Time1–8 h

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

Parts involved

transfer caseshift forktransfer case actuator

Related codes

P279AP279BP279DP279EP2771

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