U0091
Vehicle Communication Bus G (-) shorted to Bus G (+)
U0091 is an OBD-II diagnostic trouble code meaning: Vehicle Communication Bus G (-) shorted to Bus G (+). Common causes: damage to the can bus wiring harness, short circuit in one of the ecus. Estimated repair cost: $6–56.
Symptoms
- Unstable operation of the dashboard
- Lost connection with some vehicle systems
- The Check Engine light comes on
- Problems starting the engine
- Malfunctions of electronic systems
Causes
- Damage to the CAN bus wiring harness
- Short circuit in one of the ECUs
- Damaged or oxidized connectors
- Faulty relays or fuses
- Mechanical damage to wiring
How to Fix
- Check the integrity of the CAN bus wiring harness
- Inspect all connectors for damage and oxidation
- Check the functionality of all associated computers
- Use an oscilloscope to diagnose CAN bus signals
- Replace damaged wiring sections
Related codes
Error U0091 by Vehicle Brand
FAQ
What does the U0091 code mean?
U0091 is an OBD-II diagnostic trouble code that indicates: Vehicle Communication Bus G (-) shorted to Bus G (+)
What causes a U0091 error code?
The most common causes of U0091 include: Damage to the CAN bus wiring harness; Short circuit in one of the ECUs; Damaged or oxidized connectors; Faulty relays or fuses.
How do I fix a U0091 diagnostic trouble code?
To fix U0091: Check the integrity of the CAN bus wiring harness. Inspect all connectors for damage and oxidation. Check the functionality of all associated computers. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with U0091?
Do not drive — repair immediately
How much does it cost to fix U0091?
The estimated repair cost for U0091 is $6–56. Actual cost depends on your vehicle, location, and labor rates.
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