Electromagnetic Interference (EMI) Fault
Indicates a fault in the vehicle's communication lines due to electromagnetic interference.
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 vehicle's computer is getting confused because there's noise on the wires that carry information between systems, sort of like static on a radio.
What the computer is actually seeing
The ECM detects an abnormal voltage level due to EMI which causes data errors during communication with other control units.
What a healthy reading looks like
Normal signal levels for communication lines should be between 0.5V and 5V; signals above or below this range can trigger SPN 938.
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 wiring and connectors for physical damage or corrosion.
- 22. Inspect the ground connections and ensure they are clean and secure.
- 33. Verify the integrity of the communication lines with a multimeter (should show 0.5V-5V during communication).
- 44. Look for nearby electronic devices that could be causing interference and isolate them if possible.
- 55. If all checks are good, use a scan tool to clear the code and see if it returns.
Common causes
- Damaged wiring harness
- Faulty connectors
- Nearby electronic devices causing interference
- Grounding issues
- Corroded pins on connectors
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but you may experience intermittent issues with communication between control modules.
Will this code come back after resetting?
It can, especially if the underlying issue is not resolved.
Why does this code sometimes pair with other codes?
It often indicates a broader issue with the communication network which can affect multiple systems.
Working a real vehicle right now?
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