Data Link Communication Failure
The engine control unit cannot communicate with the electronic control unit properly.
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)
The engine computer is trying to talk to another computer in the vehicle but can't get a proper response. It's like trying to make a phone call, but the line is busy or dead.
What the computer is actually seeing
The ECM expects to receive specific data packets from the ECU. If the signal is low (below 0.1 volts) or erratic, it thinks there is a communication problem.
What a healthy reading looks like
Normal communication voltages typically between 2.5V and 5V.
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 wiring and connectors related to the communication link between the ECUs for damage or corrosion. If you find an issue, repair it.
- 22. Inspect the vehicle's data link connector (DLC) for bent pins or dirt. Clean or repair as needed.
- 33. Use a multimeter to check for proper voltage levels on the communication lines (should be between 2.5V and 5V). If voltage is not in range, trace wiring back to source.
- 44. If communication is still failing, swap the suspected faulty ECU with a known good one. Test to see if the issue resolves.
Common causes
- Faulty wiring or connectors between ECUs
- Failed ECU (engine control unit)
- Issues with the vehicle's data link connectors (DLC)
- Shorts or opens in the data bus circuit
- Interference from aftermarket devices
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not recommended, as it can lead to further issues and possibly a no-start situation.
Will this code come back after clearing it?
It may return if the underlying issue is not resolved, such as faulty wiring or a bad ECU.
Why might this code pair with SPN 2566?
SPN 2566 indicates two-way communication issues, which are often related to the same wiring or connector problems.
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