P0691: Fan 1 control: circuit low
The ECU sees too low a voltage on the radiator fan control circuit; the fan may not run at all or may keep running all the time.
| Code | P0691 |
|---|---|
| System | Engine and transmission |
| Group | P06xx, Control unit and auxiliary outputs |
| Type | Generic: it means the same on every make |
| Can you keep driving? | With care |
What P0691 means
The engine ECU runs the radiator fan, either directly, through a relay or through a small control module, to cool the engine when needed and whenever the air conditioning is on. This code means there is less voltage than expected on the fan 1 control circuit. Depending on how each manufacturer has designed it, that can leave the fan stopped or running non-stop.
Most common causes
- Faulty fan fuse or relay
- Loose or corroded fan or relay connector
- Chafed control wire touching earth
- Fan motor shorted or seized
- Faulty fan control module
- ECU fault (uncommon)
Symptoms
- Fan not coming on, or running all the time
- Temperature rising in traffic or at idle
- Air conditioning cooling poorly when stationary
- Engine warning light on
Can you drive with P0691?
With care You can drive, but keep an eye on the temperature gauge: if the fan is not working the engine can overheat in traffic. If it climbs above normal, stop and let it cool.
Open the bonnetthe in-depth explanation
How to check it
With the engine warm at idle, or with the air conditioning switched on, the fan should start. Some scanners can switch it on in an actuator test to see if it responds.
How to read and clear P0691 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0691 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P068D The cylinder 7 glow plug control gives a higher signal than normal
- P068E The cylinder 8 glow plug control gives a lower signal than normal
- P068F The cylinder 8 glow plug control gives a higher signal than normal
- P0690 The engine control relay monitoring signal is high
- P0692 Fan 1 control: circuit high
- P0693 The fan 2 control gives a lower signal than normal
- P0694 The fan 2 control gives a higher signal than normal
- P0695 The fan 3 control gives a lower signal than normal
- P0600 Serial communication link fault
- P0601 Internal control module memory checksum error
- P0602 Control module programming error
- P0603 Internal control module keep alive memory (KAM) error
What does code P0691 mean?
The engine ECU runs the radiator fan, either directly, through a relay or through a small control module, to cool the engine when needed and whenever the air conditioning is on. This code means there is less voltage than expected on the fan 1 control circuit. Depending on how each manufacturer has designed it, that can leave the fan stopped or running non-stop.
Can you drive with P0691?
You can drive, but keep an eye on the temperature gauge: if the fan is not working the engine can overheat in traffic. If it climbs above normal, stop and let it cool.
How do you clear P0691?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0691 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
