Chassis, generic

C0306 Transfer Case Motor A or B Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C0306 is not in the publicly available J2012 lists, and nobody uses it for a ride height sensor. GM uses it in its transfer case module (TCCM) for the two circuits that drive the shift motor: AA1Car's GM table names it Motor A or B Circuit, and bulletins PIP5080 and PIP5080B for 2012–13 Silverado, Sierra, Tahoe, Suburban, Avalanche and Yukon point to terminals at X109 and to connector X3 of the module, which carries motor circuits 1552 and 1553. Gears Magazine describes the 2013–14 Canyon and Colorado: the module powers one motor line, reads the voltage drop on the other and sets the code after four seconds of wrong values; subcodes 01, 02, 04 and F1 mean short to battery, short to ground, open and performance.

Likely causes

Loose, corroded or poorly crimped terminals at the motor or module connector
Transfer case shift motor with internal short or open winding
Faulty motor driver in the transfer case control module

Symptoms

  • Service 4WD message in the driver information centre
  • Transfer case does not shift between 2WD, 4WD and low range

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–800
Time0.5–3 h

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

Parts involved

transfer case control moduleshift motortransfer case wiring

Related codes

C0308C0310C0327C0387

References: aa1car.com, static.nhtsa.gov, static.nhtsa.gov, gearsmagazine.com.