Redundant Electronic Control Module A
Indicates a fault with the redundant ECM 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)
The engine control module is designed to have a backup system to ensure reliability. If there's a fault, it means the backup system isn't working correctly, which could lead to engine performance issues.
What the computer is actually seeing
The primary ECM detects a failure in the redundant module. It expects a certain response from the redundant ECM within specified time frames (typically less than 100 ms).
What a healthy reading looks like
The primary ECM must receive an acknowledgment signal from the redundant ECM within 50 ms after it sends a request.
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 between the primary and redundant ECM for damage or corrosion. Repair any issues found. Decision Point: Are the connections intact? Yes - Go to Step 2; No - Repair and retest.
Common causes
- Faulty redundant ECM
- Wiring harness issues
- Connector corrosion or damage
- Software glitches in the ECMs
Typical repair cost
$$$
Related codes
Frequently asked questions
Can I still drive the vehicle with this code?
Yes, but monitor performance closely and plan to repair soon, as performance may be impacted.
Will this code come back after clearing it?
If the underlying issue isn't resolved, it likely will return.
Why does this code sometimes pair with SPN 1258?
SPN 1258 indicates a fault in the primary ECM, which may trigger SPN 1259 if the redundant system is also involved.
Working a real vehicle right now?
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