Rear Axle Differential Lock Motor
The C0840 code means the vehicle's onboard diagnostic system has detected: Rear Axle Differential Lock Motor. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $200 - $900 (parts and labor)
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Common Symptoms
- 4WD warning light on
- Differential lock indicator on
- Transfer case grinding noise
- Front axle engagement issues
Probable Causes (Ranked by Likelihood)
- Failed axle speed sensor Very High
- Damaged differential lock motor High
- Transfer case motor failure Moderate
- Low differential fluid level Low
Step-by-Step Diagnostic Procedure
-
Scan 4WD module for specific codes
-
Test differential lock motor operation
-
Check transfer case fluid level
-
Inspect axle sensor wiring and connectors
Frequently Asked Questions
What does code C0840 mean?
C0840 indicates a fault with the rear axle differential lock motor.
Can I drive with C0840?
You can drive short distances at low speeds. Avoid highway driving until repaired.
How much does it cost to fix C0840?
Typical repair costs are $200 - $900 (parts and labor).
Sources
This page is built from documented references. Verify against your own service info before repair work.
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