Data Link Diagnostics - Unforeseen Data Link Communication Failure
The ECM detects a communication problem on the data link.
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)
Your engine control module (ECM) is having trouble talking to other computers in the vehicle, like the transmission control module.
What the computer is actually seeing
The ECM expects to receive data packets from other control modules at regular intervals but sees a timeout, indicating a communication failure.
What a healthy reading looks like
Data packets should be received within 500 milliseconds. If no packets are received in this timeframe, the code is triggered.
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 data link connections and wiring for physical damage. Repair or replace as needed.
- 22. With the engine off, use a multimeter to check for continuity in the data link wiring. Resistance should be below 5 ohms.
- 33. Ensure all related control modules are powered and ground is present; voltage should be around 12V with the key on.
- 44. If no wiring issues are found, use a scanner to check for other fault codes. If multiple codes exist, diagnose those first.
- 55. If no other codes are present, try unplugging and replugging all related modules to reset the data connection. Then check for the return of the fault code.
Common causes
- Bad wiring or connectors on the data link
- Faulty ECM or TCM
- Issues in data bus modules
- Failure of any device in the communication loop
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
No, the communication failure can affect critical systems, so drive with caution until repaired.
What happens if I ignore this code?
Ignoring this code can lead to more serious issues, including failure of critical vehicle systems.
Why does this code pair with SPN 1684?
Both codes indicate problems related to data link communication; they often arise from similar issues.
Working a real vehicle right now?
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