Powertrain, generic (extended)

P279F Four Wheel Drive (4WD) Range Signal Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P279F means the wired 4WD range signal is below the lowest valid level. Many transfer cases report their range through a resistor-coded switch or a position sensor that produces a defined voltage for each of high, low and neutral; a reading under the lowest of these bands points to a short to ground, a missing sensor supply or a sensor that pulls the line down. No manufacturer documents P279F publicly; GM's 2008 Two-Mode Hybrid data list the circuit code P279D for the same range information, and CARB 13 CCR 1968.2 requires range checks on such inputs. The high-side fault is P27A0, the plausibility fault P279E. Look for chafed harness sections near the transfer case and exhaust and for corroded connectors before replacing the encoder.

Likely causes

Range signal wire shorted to ground near the transfer case
Sensor reference voltage missing
Range switch or encoder failed with low output

Symptoms

  • 4WD range indicator dark or flashing
  • 4WD low or range changes unavailable
  • Warning lamp on

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–800
Time0.5–3 h

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

Parts involved

four wd range sensorwiring harness

Related codes

P279DP279EP27A0

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