C0387 Code: Transfer Case Shift Unable to Complete

What the C0387 code means

The transfer case on 4x4 trucks with electronic control shifts between 2H, 4H and 4L using an electric motor. An encoder on the motor tells the module the exact position it is in.

With the C0387 code, the shift motor tries to move the mechanism and the encoder does not confirm that it reached the requested position.

Many failures happen because the shift motor or its encoder end up with moisture or corrosion, since they are mounted on the outside of the case.

Important: many C and B codes are not generic. The definition on this page is the most widespread one, used by General Motors and most generic scan tools, but on other makes the same number can mean something else. Always confirm the code text with a scan tool that reads the right module (ABS, body or airbag).

C0387 code symptoms

• 4x4 warning light or 4WD service light flashing or on.
• The drive does not change between 2H, 4H and 4L.
• The vehicle may be stuck in one drive mode.

Likely causes of the C0387 code

1. Seized or failed shift motor. Confirm it with the tests in the diagnosis section.
2. Connector or encoder with corrosion. Check the lock, the pins and any moisture or corrosion.
3. Shift fork or internal mechanism that is stuck. Confirm it with the tests in the diagnosis section.
4. Old oil in the case. Check the level, the condition and the viscosity.

How to diagnose the C0387 code step by step

1. Check the transfer case oil level and condition.
2. Inspect the shift motor connector for moisture or corrosion.
3. Read the encoder position on the scan tool while you request a shift.
4. Check the motor supply and ground.
5. Check the 4x4 system fuse.

How to fix the C0387 code

• Clean and seal the connector.
• Replace the shift motor together with its encoder.
• Repair the wiring.
• Recalibrate the case with the scan tool if the manufacturer requires it.

Technical reference data

• The encoder usually has several tracks that form a code depending on the position.
• These values are approximate. Check the manufacturer data for your vehicle.

Brand-specific notes

If the motor runs but the case never arrives, the problem may be mechanical inside the case. Fresh fluid and a proper recalibration are worth trying before a teardown.

C0387 on Chevrolet and GMC

This code is very common on the Chevrolet Silverado, Tahoe and Suburban, and on the GMC Sierra and Yukon, with an electronically controlled transfer case.

Frequently asked questions about C0387