Left Rear Door Module Communication Circuit Malfunction
The B0393 code means the vehicle's onboard diagnostic system has detected: Left Rear Door Module Communication Circuit Malfunction. This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- easy
- Estimated cost
- $40 - $250 (parts and labor)
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Common Symptoms
- Left Rear door ajar light stays on
- Interior lights stay on with doors closed
- Left Rear door not detected as closed
- Warning chime sounds with left rear door closed
Probable Causes (Ranked by Likelihood)
- Faulty left rear door module communication Very High
- Damaged left rear door wiring High
- Door latch not fully engaging Moderate
- BCM door input circuit fault Low
Step-by-Step Diagnostic Procedure
-
Test left rear door module communication operation
-
Check left rear door wiring continuity
-
Inspect door latch mechanism
-
Verify BCM door input signals
Frequently Asked Questions
Why does my door ajar light stay on?
Usually caused by a faulty door jamb switch or a door latch that is not fully closing.
Can a door ajar warning drain my battery?
Yes, if it keeps interior lights on, it can drain the battery overnight.
How do I test the door switch?
Use a multimeter to check continuity when the door is fully closed. The switch should close the circuit.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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