U0040
Vehicle Communication Bus B (+) Low
U0040 is an OBD-II diagnostic trouble code meaning: Vehicle Communication Bus B (+) Low. Common causes: open or short circuit in the can b bus circuit, wiring harness damage. Estimated repair cost: $17–56.
Symptoms
- Incorrect operation of systems connected to the CAN B bus
- Malfunction indicator light comes on
- Problems with climate control
- Errors in other systems related to the CAN B bus
Causes
- Open or short circuit in the CAN B bus circuit
- Wiring harness damage
- Malfunction of one of the modules connected to the CAN B bus
- Corrosion or poor contact in connectors
- Problems with module power supply
How to Fix
- Check the integrity of the CAN B bus wiring harness
- Inspect connectors for corrosion or damage
- Check the power supply of the modules connected to the CAN B bus
- Diagnose faulty modules using a scanner
- Repair only from an authorized dealer
Related codes
Error U0040 by Vehicle Brand
FAQ
What does the U0040 code mean?
U0040 is an OBD-II diagnostic trouble code that indicates: Vehicle Communication Bus B (+) Low
What causes a U0040 error code?
The most common causes of U0040 include: Open or short circuit in the CAN B bus circuit; Wiring harness damage; Malfunction of one of the modules connected to the CAN B bus; Corrosion or poor contact in connectors.
How do I fix a U0040 diagnostic trouble code?
To fix U0040: Check the integrity of the CAN B bus wiring harness. Inspect connectors for corrosion or damage. Check the power supply of the modules connected to the CAN B bus. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with U0040?
Yes, but get it checked soon
How much does it cost to fix U0040?
The estimated repair cost for U0040 is $17–56. Actual cost depends on your vehicle, location, and labor rates.
See also: Russian version · NationStat