Powertrain, generic (extended)

P27A0 Four Wheel Drive (4WD) Range Signal Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P27A0 is logged when the line reporting which transfer case range is engaged (4WD high, 4WD low, neutral) reads above its highest valid level. Range encoders usually present a defined voltage or resistance band for each position; a value above all bands typically means the wire is open and pulled up inside the module, the encoder lost its ground, or the line touches a battery feed. No manufacturer documents P27A0 publicly. GM's 2008 Two-Mode Hybrid tables carry the same range information under P279D, and CARB 13 CCR 1968.2 asks for out-of-range checks on such inputs. P279F is the low-side partner, P279E the plausibility fault. With the range unknown, the module may refuse range changes or fall back to a default torque strategy.

Likely causes

Range signal wire or encoder ground interrupted (corroded or loose connector near the transfer case)
Signal wire chafed against a powered conductor
Transfer case range encoder or switch defective

Symptoms

  • 4WD indicator flashing or showing no range
  • Shift between 4WD high and low refused
  • Warning lamp or driveline message

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

P279DP279EP279FP2771

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