P0691: Cooling Fan 1 Control Circuit Low
What to do
If the fan runs constantly, that is irritating rather than dangerous — drive normally and get it fixed. If the fan never runs, watch the temperature gauge closely and avoid stationary traffic, because overheating causes expensive damage quickly.
What this code means
The primary cooling fan control circuit is reading low — a short to ground, or a relay welded closed. A fan running continuously is the usual presentation: noisy and hard on the battery, but not a threat to the engine.
It is the opposite failure that is dangerous, so confirm which one is actually happening before deciding how urgent this is. A fan that runs constantly is an annoyance; a fan that never runs will overheat the engine in traffic.
Likely causes
Start here
- Failed cooling fan relay · easy
- Signal wire shorted to ground · moderate
- Corroded or loose connector · easy
Less common
- Failed cooling fan motor · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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