FAN 1 CONTROL SIGNAL
Indicates an active fault in the control signal for Fan 1.
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 (ECM) is responsible for turning the cooling fan on or off based on engine temperatures. When the system detects that the fan isn’t responding correctly to the ECM's signals, it triggers this fault code, often due to a wiring issue or a bad fan motor.
What the computer is actually seeing
The ECM expects to see a specific voltage on the fan control circuit. Typically, a low signal indicates the fan should be off (0-1V) and a high signal indicates it should be on (10-14V), depending on the system design.
What a healthy reading looks like
When the fan is off, you should see 0-1V. When the fan should be on, expect around 10-14V.
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 all related wiring and connectors for damage or corrosion. Repair as necessary. Decision: If wiring is intact, proceed to step 2; if damaged, repair wiring and retest.
- 22. Verify the operation of the cooling fan. Disconnect the fan and apply direct battery voltage to it. Decision: If the fan runs, proceed to step 3; if not, replace the fan.
- 33. Test for voltage at the fan connector while operating the vehicle. Expect to see appropriate voltage as specified. Decision: If voltage is present, ECM may be faulty; if absent, inspect further for wiring issues or connection problems.
Common causes
- Bad cooling fan motor
- Damaged wiring or connectors
- Faulty ECM
Typical repair cost
$$
Related codes
Frequently asked questions
Can I still drive the vehicle with this fault?
Yes, but keep an eye on the engine temperature and fix it soon to avoid overheating.
Will this code come back after clearing it?
It might, especially if the underlying issue isn't fixed.
Why does this code sometimes pair with SPN 596?
SPN 596 is related to the fan 2 control signal, indicating there might be a broader issue affecting all fan controls.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →