U0004
High Speed CAN Communication Bus (+) Low
Severity: HIGH
Symptoms
- Unstable operation of electronic systems
- Malfunction indicator light comes on
- Lost connection with some modules
- Problems starting the engine
- Incorrect instrument readings
Causes
- Open or short circuit in the CAN (+) circuit
- Wiring harness damage
- Malfunction of one of the modules on the CAN bus
- Poor connection or corroded connectors
- Problems with module power supply
How to Fix
- Check the integrity of the CAN bus wires (+)
- Inspect connectors for corrosion or damage
- Check the power and ground of the modules on the CAN bus
- Disable the modules one by one to identify the faulty one.
- Check resistance and voltage on the CAN bus