C0374 on GMC: How to Diagnose & Fix
Transfer Case / Automatic 4WD System Malfunction (manufacturer-specific)
1 GMC model · 1 documented issue · $250-$900 repair
C0374 on GMC by model: symptoms, diagnosis and fix
The electric-shift NV246/NV263 transfer case on Sierra 2500HD trucks is positioned by an encoder motor mounted to the case, with a sensor ring inside it reporting shaft position back to the Transfer Case Control Module. Moisture and road salt corrode the encoder motor and its sensor ring, and the dash selector switch itself develops open contacts. When the TCCM loses a valid position signal it illuminates "Service 4WD" and refuses to shift. The classic pattern owners describe is a truck that will still drop into 4LO but will not engage 4HI, because the module can drive the case to its travel extremes but cannot stop it at the intermediate position. C0327 is the code that identifies it.
Common Symptoms
- "Service 4WD" message on the driver information center
- 4HI will not engage but 4LO will
- No response at all from the 4WD selector buttons
- Buttons flashing continuously
- Grinding or clunking when attempting to shift the case
How to Fix
Read the TCCM codes before replacing anything - C0327 points at the encoder motor or its sensor ring, while a dead switch produces no motor sound at all. On many trucks only the encoder sensor ring inside the motor needs replacing, which is far cheaper than the complete motor. A failing encoder motor can short and damage the TCCM, so both are sometimes needed; a replacement TCCM must be programmed to the vehicle's 4WD configuration with a dealer-level scan tool. No recall applies.
Sources for this issue (3)
C0374 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does C0374 mean on a GMC?
C0374 stands for "Transfer Case / Automatic 4WD System Malfunction (manufacturer-specific)." C0374 is a manufacturer-specific chassis code (commonly seen on GM four-wheel-drive vehicles) that generally indicates a general malfunction in the transfer case / automatic four-wheel-drive control system. When it sets, the Auto 4WD mode is typically unavailable and a 'Service 4WD' message may appear. Because the exact subsystem can vary by maker and model, the precise fault should be confirmed with a factory-level scan tool. This code affects drivetrain/4WD operation rather than braking. On GMC it is documented across 1 model: Sierra 2500HD.
What are the most common causes of C0374?
The most common causes of C0374 are: Faulty transfer case control module, Transfer case encoder/actuator motor fault, Damaged wiring or connectors in the 4WD circuit, Mode-select switch fault, Low system voltage or poor ground, Mechanical fault within the transfer case, Software/calibration issue in the 4WD module. The specific cause varies by vehicle.
How much does it cost to fix C0374 on a GMC?
Published repair estimates on GMC range from $250 to $900 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for C0374 on a different make?
View C0374 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.