Chassis, generic

C0310 Transfer Case Motor A/B Circuit Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C0310 is not listed in any publicly available J2012 table; no maker uses it for a rear left ride height sensor. GM assigns the number to the transfer case shift motor: it is in PIP5094, AA1Car gives the GM wording Motor A/B Circuit Open, and Dorman describes it for GM trucks and SUVs of 1998 to 2005. The transfer case module drives the motor through two lines, one switched to supply and the other to ground depending on direction. When it commands a low level on a line and reads a high voltage back instead, it concludes that line A, line B or the motor winding is open and stores C0310. Shifting is then blocked and Service 4WD lights up. A broken motor pigtail or connector is the usual cause.

Likely causes

Broken motor control wire or pigtail exposed under the vehicle
Corroded or unseated connector at the shift motor
Open winding or worn brushes in the shift motor

Symptoms

  • Service 4WD lamp on, 4WD switch lights flash
  • Transfer case stays in its last range

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–700
Time0.5–2.5 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

C0306C0308C0327

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