P0691🔧 Engine cooling (electric radiator fan)Stop and fix promptly

P0691: Cooling Fan 1 Relay Control Circuit Low (Meaning, Causes, Fixes)

Reviewed 2026-10-25 · Based on 2 cited source(s)

What P0691 means

Electric fans pull air through the radiator when the car isn't moving fast enough to cool it, such as in stop-and-go traffic, on hot days or with the A/C on. The powertrain computer (PCM) switches the fan on and off based on the engine coolant temperature sensor. OBD-Codes.com explains that the PCM turns the fan on by grounding the cooling fan relay's control circuit: that circuit sits near battery voltage when the fan is off and near zero when the fan is commanded on. P0691 is set when the PCM sees low voltage on that circuit while cooling fan 1 is supposed to be off. RepairPal defines the code a little more broadly as 'Fan 1 Control Circuit Low' and says the PCM sets it when it can't control the cooling fan as desired. It is a generic code for 1996 and newer vehicles, and repair steps vary by make and model. The sources differ on symptoms: OBD-Codes.com lists engine overheating and the check engine light, while RepairPal also says the fans may stay on all the time and the A/C may not work. They also differ on causes: OBD-Codes.com names the fan relay, a blown fan fuse and, rarely, the PCM, while RepairPal adds a failed fan control module, a failed fan motor and wiring problems. P0480 and P0481 are related cooling fan control codes.

Severity: can I keep driving?

Stop and fix promptly

Get it fixed soon. OBD-Codes.com says overheating from cooling fans that don't run is very probable, so use caution driving and repair it as soon as possible. RepairPal rates P0691 Urgent, meaning immediate action is needed.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. Blown cooling fan 1 fuse (OBD-Codes.com says this is the most common cause in the author's experience)
  2. Bad cooling fan 1 relay (OBD-Codes.com, RepairPal)
  3. Failed cooling fan motor (RepairPal); OBD-Codes.com says a seized fan motor can blow the fuse once the engine warms up
  4. Failed engine cooling fan control module (RepairPal)
  5. Wiring problem, including a direct short between the fuse and the relay (OBD-Codes.com, RepairPal)
  6. Faulty engine computer (PCM), which OBD-Codes.com says is rare (OBD-Codes.com, RepairPal)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. Find the cooling fan fuse (your owner's manual or fuse box lid shows which one), pull it and look at it. OBD-Codes.com says you can usually tell by eye whether it's blown.
  2. If it's blown, replace it with a fuse of the same amperage. OBD-Codes.com says if the new fuse blows right away, look for a direct short between the fuse and the relay; if it blows once the engine reaches operating temperature, suspect the fan motor.
  3. With the engine and ignition off, try spinning the fan blades by hand. OBD-Codes.com says they should spin freely; if they don't, the fan motor is seized and needs replacing.
  4. If the fuse is good, OBD-Codes.com says the cooling fan relay is the most likely cause. Swapping in a known-good relay of the same type is a quick test.
  5. Watch the temperature gauge closely while this code is set, and pull over and shut the engine off if it starts to overheat.

Typical fixes

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

  • The engine is overheating or the temperature gauge is climbing
  • A new fan fuse blows right away, which points to a short you'll need a wiring diagram to trace
  • Your car uses a cooling fan control module instead of a simple relay
  • Tests point to the engine computer

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with P0691?

Only with care. OBD-Codes.com says overheating from cooling fans that don't run is very probable and it should be repaired as soon as possible, and RepairPal rates it Urgent. Keep an eye on the temperature gauge and stop if it climbs.

What is the most common cause of P0691?

OBD-Codes.com's author says a blown cooling fan fuse is the most common cause in their experience, followed by a bad cooling fan relay. RepairPal also lists the fan motor, a fan control module, wiring and the PCM.

Why are my cooling fans running all the time with P0691?

RepairPal lists fans that stay on all the time as a symptom of P0691, along with A/C problems and overheating. OBD-Codes.com focuses on fans that don't run and cause overheating.

How much does it cost to fix P0691?

Neither source gives a repair cost for P0691. A fuse or relay is a much smaller job than a fan assembly or engine computer, so find the cause before buying parts.

Sources

  1. OBD-Codes.com: P0691 Cooling Fan 1 Relay Control Circuit Low (Daniel Young, ASE Master Technician)
  2. RepairPal: P0691 Fan 1 Control Circuit Low (rated Urgent)

Last reviewed 2026-10-25. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.