P0691
Cooling Fan 1 Control Circuit Low
Cooling Fan 1 Control Circuit Low: the control-circuit voltage is below the expected range. Reduced cooling-fan control can let the engine or A/C condenser overheat.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
Common causes
Ordered by how often each turns out to be the cause.
- Fan relay defectiveCommon
- Wiring shorted to groundPossible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- Cooling Fan
- Cooling Fan Relay
P0691 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.