Control Module Communication Bus 'A' Off
There's a communication problem between modules on the vehicle's bus system.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
Multiple control modules, like the engine or transmission control units, communicate over a network. If a module stops talking or you lose the connection, it can trigger this code.
What the computer is actually seeing
The main computer notices that it isn't receiving data from one of the modules on the communication bus 'A'.
What a healthy reading looks like
Modules should communicate within specific data packets, typically at a frequency of 500 Kbps, and respond within milliseconds.
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 the vehicle's battery voltage; should be between 12.4V and 14.8V while running. If not, correct before further testing.
- 22. Inspect all related wiring and connectors for damage or corrosion between affected modules; repair as needed. Decision: Is everything intact? Yes - go to step 3; No - fix wiring/connectors and recheck code.
- 33. Use a scan tool to check for additional communication-related codes. Decision: Are there other codes present? Yes - note those codes; No - proceed to step 4.
- 44. With the scan tool, perform a communication test between modules; ensure they reply as expected. Decision: Do all modules respond? Yes - go to step 5; No - identify failed module and replace it.
- 55. Clear the codes and take the vehicle for a test drive. Check for the return of U0073 after rechecking connections. Decision: Comes back? Yes - suspect more extensive network issues; No - repair is successful.
Common causes
- Faulty wiring or connectors in the CAN bus system
- Failed control module
- Corrosion or damage at connector
- Signal interference from aftermarket devices
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's drivable, but you'll likely notice issues with activities like shifting or engine performance. Address it soon.
Will this code come back after I fix it?
If you resolve the underlying issue, like fixing a connector, it shouldn't return. However, if there's a deeper problem, it might.
Why does this code pair with other communication codes?
They often happen together because multiple control modules rely on the same communication system. If one module fails, it can affect the others.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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