Control Module Communication Fault
There is a communication issue between control modules.
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What it means (plain English)
The vehicle's control modules (like the engine, transmission, ABS) aren't talking to each other properly. This could be due to a bad wire, connector, or an issue in one of the control modules themselves.
What the computer is actually seeing
The vehicle computer is sensing that it can't communicate with one or more control modules over the internal network and is receiving error signals indicating a communication failure.
What a healthy reading looks like
Communication signals on the CAN bus should be at 2.5V (idling) and fluctuate between 1V and 4V when active data is sent. A consistent fault indicates a break in communication.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check all related wiring and connectors for damage or corrosion. Ensure they're securely connected. Decision: If damaged, repair/replace wiring. If not damaged, proceed to step 2.
- 22. Inspect and test the fuses related to the affected control modules. Decision: Replace any blown fuses found. If fuses are good, proceed to step 3.
- 33. Scan for other codes that may indicate a specific module issue. Decision: If other related codes are present, focus diagnosis on those modules. If no other codes are found, proceed to step 4.
- 44. Check the power supply to the affected modules (look for 12V+ on pin when the vehicle is on). Decision: If power is missing, troubleshoot the power supply circuit. If power is present, proceed to step 5.
- 55. Confirm functionality of the modules by swapping them (if possible) or using a known good module for testing. Decision: If the swapped module resolves the communication issue, replace the faulty module.
Common causes
- Bad wiring or connectors in the communication circuit
- Faulty control module
- Electrical interference from other devices
- Blown fuses related to the control modules
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive the vehicle with this code?
It's not recommended to drive until the issue is fixed as this can affect safety and functionality.
Will this code come back after clearing it?
If the underlying communication issue is not resolved, the code will likely reappear.
Why does this code often pair with other codes?
When communication fails, it often indicates problems with multiple control modules, which can generate related fault codes.
Working a real vehicle right now?
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