C0387 on Cadillac: How to Diagnose & Fix
Manufacturer-Specific Chassis Code (commonly transfer case / shift-related on GM)
1 Cadillac model · 1 documented issue · $250-$600 repair
C0387 on Cadillac by model: symptoms, diagnosis and fix
The transfer case encoder motor that controls AWD/4WD engagement fails, causing the "Service 4WD" message and preventing 4WD engagement. The position sensor inside the encoder motor sends incorrect signals. The transfer case may also develop an internal fluid leak past the front output seal.
Common Symptoms
- Service 4WD message on dash
- 4WD not engaging
- Grinding noise when shifting to 4WD
- Transfer case stuck between modes
How to Fix
Replace the encoder motor on the transfer case. The motor is externally mounted and accessible. After replacement, a transfer case relearn procedure must be performed with a scan tool. Check and top off the transfer case fluid with the correct Auto-Trak II fluid.
Sources for this issue (1)
C0387 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 C0387 mean on a Cadillac?
C0387 stands for "Manufacturer-Specific Chassis Code (commonly transfer case / shift-related on GM)." C0387 is a manufacturer-specific chassis code that falls in a range largely reserved/non-standardized under SAE, so its exact meaning varies by manufacturer. On many GM vehicles it appears alongside transfer-case encoder/shift codes and is generally associated with an inability to complete a requested shift or a related transfer-case/electronic shift fault. Because the precise definition is not standardized, the code should be confirmed against the specific vehicle's service information. In general it points to a chassis driveline or shift-control concern rather than the engine itself. On Cadillac it is documented across 1 model: Escalade ESV.
What are the most common causes of C0387?
The most common causes of C0387 are: Transfer case encoder motor or shift fault (GM applications), Damaged or corroded wiring/connectors in the affected circuit, Failed shift motor or actuator, Control module (e.g., transfer case control module) fault, Low system voltage or poor ground, Mechanical binding in the shift mechanism. The specific cause varies by vehicle.
How much does it cost to fix C0387 on a Cadillac?
Published repair estimates on Cadillac range from $250 to $600 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 C0387 on a different make?
View C0387 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.