The cooling fan control circuit is reading low. If the fan will not run, the engine will overheat in traffic even though it is fine on the move.
P0691 — also written PO691, P 0691, 0691 — is the OBD-II code for fan 1 control circuit low. Same code, same fix: this page covers every spelling of it.
P0691 is a electrical fault code, typically costing £120–£650 to put right in a UK garage.
What causes P0691?
- Failed fan control module or resistor pack
- Seized fan motor
- Blown high-current fuse
- Corroded connector
How P0691 is fixed
- Run the fan on command with a scan tool
- Replace the fan module or motor
- Repair the fuse box terminal
P0691 repair cost in the UK
Most P0691 repairs land between £120–£650 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Can you drive with P0691?
Not in traffic. Watch the temperature gauge closely and pull over if it climbs.
Urgency: high.
What P0691 is telling you
Electrical codes are circuit faults, not component faults. The ECU is reporting a voltage or resistance outside the range the circuit should ever produce, and the cause is as often a connector, an earth or a chafed wire as it is the part at the end of it.
On P0691 specifically — fan 1 control circuit low — the stored code records the moment that check failed, not the moment the part gave up. That gap is why two cars with the same code can need completely different repairs.
How P0691 is diagnosed properly
Each of the known causes is ruled in or out in cost order, cheapest and most likely first. On P0691 that means working through them like this:
- Failed fan control module or resistor pack — checked for outstanding manufacturer updates before any hardware is touched.
- Seized fan motor — confirmed with live data before any part is bought.
- Blown high-current fuse — confirmed with live data before any part is bought.
- Corroded connector — opened, inspected for green corrosion and spread pins, and back-probed rather than unplugged, so the reading is taken with the circuit live.
An hour of diagnostic time on P0691 routinely saves more than it costs, because the alternative is buying the most expensive part on that list and hoping.
The repairs that actually clear P0691
- Run the fan on command with a scan tool
- Replace the fan module or motor
- Repair the fuse box terminal
After the repair the code is cleared and the car is driven until the relevant readiness monitor completes, rather than handed back as soon as the light goes out. A code that has only been erased will come straight back on the next drive cycle.
What happens if P0691 is ignored
This is a stop-and-sort fault rather than a wait-for-the-service fault. Ignoring it risks turning a sensor-money repair into a component-money one.
For reference, P0691 typically lands at £120–£650 all-in at an independent garage in the UK — main-dealer quotes for the same job usually sit above that.
Getting P0691 looked at
Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0691 is showing on your car, bring the scan results with you — we will read the live data ourselves, tell you which of the causes above it actually is, and price the repair before any work starts.