CoolingGeneric OBD-II codeUrgency: Garage soon
Code P0691: cooling fan 1: control circuit low
What code P0691 means
The ECU has detected that the voltage in the cooling fan 1 control circuit is lower than expected. TroubleCodes.net interprets this as the radiator fan not working, or working worse than it should.[2]
It is a generic OBD-II code (it starts with P0), so it means the same on any make. AutoDTCs describes it for two-speed fans.[1][3]
Original definition (SAE J2012): Fan 1 Control Circuit Low[1]
Causes of P0691
From most to least likely, according to the sources.
Symptoms
- Warning light on the dashboard.[4]Engine warning light: faults that cause it
- Engine temperature rising, especially at low speed or in traffic jams.[2][4]Overheating: faults that cause it
- Poorer air conditioning performance, especially when stationary.[2]Air con not cooling: faults that cause it
How to diagnose P0691
In order: from the most likely and cheapest to check to the most expensive.
- 1Start with the battery: check that it gives about 12.6 V at rest and between 13.8 and 14.5 V with the engine running.[2]
- 2Check the fan fuse and its relay, and clean or repair the connectors.[2][4]
- 3With the air conditioning on full, check that voltage reaches the fan connector and that the motor turns when powered directly.[2]
- 4TroubleCodes.net warns against replacing the fan without doing these tests first, because there may be a cheap fix.[2]
Can I keep driving with P0691?
Garage soon
Without the fan the engine can overheat in traffic jams or at low speed. AutoDTCs rates it moderate severity: fix it soon, and stop if the temperature climbs.[2][3]
Documented faults related to P0691
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
Thermostat and cooling system: the most serious faults by engine and car
- High severityFrequency: CommonBMW M54Thermostat and water pump failureThe M54's thermostat, housing and water pump contain plastics that become brittle and fail. If left unattended, overheating can warp the aluminium cylinder head. It is advisable to replace them together.Appears at around 129,000 km
- High severityFrequency: CommonBMW M54Cracked expansion tank and coolant leakThe plastic expansion tank degrades over the years and eventually cracks. It is cheap compared with the cost of overheating an M52/M54, and age matters more than mileage.
- High severityFrequency: CommonPorsche V8 and V6 (Cayenne and Panamera)Cracked plastic coolant pipes on the Cayenne V8The first Cayenne V8s (the 4.5) have plastic coolant pipes under the intake manifold that crack with age and cause coolant loss; Porsche switched to aluminium around 2006-2007. A Canadian workshop says it also affects the later 4.8.
- High severityFrequency: Common1.4/1.6 VTiFragile water pump (and expansion tank or heat exchanger, depending on displacement)Yes: fiches-auto.fr describes a fragile water pump in both the 1.4 VTi (with an expansion tank prone to leaks) and the 1.6 VTi (with the heat exchanger), a cooling problem that the turbocharged 1.6 THP inherits from this naturally aspirated version.
Wiring, connectors and short circuits: the most serious faults by engine and car
- Critical severityFrequency: OccasionalBMW N62 / N63Additional turbo coolant pump with a risk of short circuit and fireIn 2011 BMW recalled 5, 6 and 7 Series, X5 and X6 models built between 2007 and 2011 because of the additional turbo coolant pump: moisture, a short circuit and, in extreme cases, a fire. In 2012 there was another campaign for a crack in the pump, with a more robust version.
- High severityFrequency: Occasional1.3 TCeBlown fuel pump fuseOn the Renault Captur II and Clio V with the 1.3 TCe engine, a 20-amp fuse can blow and leave the car without an engine. According to L'argus, in April 2021 this fault still had no factory fix; the official service centre's diagnosis includes checking, and sometimes replacing, the catalytic converter.
- High severityFrequency: OccasionalM264/M254Poorly tightened 48 V earth wiring in the mild-hybrid system (fire risk)Mercedes-Benz has issued several recalls (2022-2025) because the 12 V and 48 V earth connections of some cars with a 48 V system may be poorly tightened: resistance rises, the connection heats up and a fire cannot be ruled out. The official workshop checks them and repairs them if necessary in an hour or more.
- High severityFrequency: Occasional1.9 TDIUnit injector tappet wear and injector wiring damageOn the unit injector system, the tappets that operate the injectors can wear if the oil is not changed on time, and the injector wiring can be damaged by contact with oil, causing misfires or loss of power.
- Critical severityFrequency: CommonRover 75Seat SRS connector fault with airbag and seatbelt warning light onAuto Express warns that the Rover 75's seat SRS connector can cause the airbags to fail, and dealers were fixing it with revised connectors. The Dutch APK inspection puts the airbag or seatbelt fault warning among the most frequent defects across almost all series.
- Critical severityFrequency: OccasionalAlfa Romeo GiuliettaShort circuit from badly routed wiring that can prevent gear shifting (KBA campaign, 2010-2015)Yes: according to Germany's KBA, on Alfa Romeo Giulietta cars built between 2010 and 2015 inadequate cable routing could cause a short circuit and, as a result, gear-shift failure.
Engine sensors: the most serious faults by engine and car
- High severityFrequency: Occasional2.0 DTI and 2.2 DTIVP44 injection pump and air mass meter failureGerman Wikipedia documents recurring failures of the Bosch VP44 injection pump and the air mass meter in the early years of this engine. An owner testimony for this engine describes the pump being replaced at 192,500 km, at a cost the owner calls «prohibitive».
- Medium severityFrequency: Common2.0 TDIClogged particulate filter or faulty pressure sensorThe 2.0 TDI's particulate filter clogs if the car mostly makes short journeys, because it never gets to regenerate; sometimes the fault is just the differential pressure sensor. Cleaning it costs around €200 and replacing it, €800 to €3,000.Repair (garage): €800–€3,000
- Medium severityFrequency: Common1.4 and 1.6 8vCrankshaft position sensor failure (TDC sensor)The crankshaft position sensor (capteur PMH, or TDC sensor) appears repeatedly in the reliability sources for the Clio II, the Kangoo I and the Dacia Logan I with this engine, with hard cold starting or stalling as the main symptoms. It is a cheap part, but the failure can leave you stranded.
- Medium severityFrequency: Common1.4 and 1.6 16vCrankshaft position sensor failureThe crankshaft position sensor (capteur PMH) appears repeatedly in the reliability sources for almost every generation with this engine, with hard cold starting, stalling or the car cutting out unexpectedly. It is a cheap part, but the failure can leave you stranded.
Frequently asked questions
Can I drive with code P0691?
With care and watching the temperature, especially in town or at low speed. If the gauge climbs, stop the engine: overheating can cause serious damage.[2][3]
Does the fan have to be replaced?
Not always. First check the fuse, relay, connectors and wiring, which are cheaper and more common causes than the fan motor.[2][4]
Is P0691 the same as P0480?
No. They are different cooling fan control codes; each has its own definition in the standard.[1]
Will I pass the MOT with code P0691?
If the code has switched on the engine warning light, no: with that light on, the inspection records a serious defect, and on Euro 5 and Euro 6 cars the ITV (Spain's roadworthiness inspection, similar to the MOT) also reads the OBD diagnostic system. Repair the fault before you go; clearing the code just before the inspection does not help either, because it counts as a serious defect.[5]
Not sure what is wrong with your car? Describe what you notice in the symptom diagnosis or see all fault codes.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- P0691 DTCDTCSearch · Technical documentation · consulted 29 October 2026
- P0691 trouble codeTroubleCodes.net · Technical documentation · consulted 29 October 2026
- P0691 diagnostic trouble codeAutoDTCs · Technical documentation · consulted 29 October 2026
- OBD Fehlercode P0691CarWiki · Technical documentation · consulted 29 October 2026 · in German
- Desmontando mitos: ¿puede pasar mi coche la ITV con el testigo de «avería motor» encendido?Diariomotor · Motoring press · published 8 March 2021 · consulted 2 October 2026 · in Spanish