What does it mean?
This code says the charge air cooler cooling fan keeps running when it should be switched off. The module commands the fan off but still sees evidence that it is turning, either through a feedback signal, through the current the circuit draws, or because the fan can be heard running with the ignition off. A fan that cannot be switched off usually means the power path to it has been completed outside the module's control: a relay whose contacts have welded together, or a control wire that has found battery voltage. A permanently running fan drains the battery when the vehicle is parked and shortens the life of the motor. On many vehicles this fault is discovered because the customer hears the fan long after switching off.
Symptoms
- Fan running continuously, including after the ignition is switched off and the vehicle is locked
- Battery going flat when the car is left standing overnight
- Constant fan noise while driving even in cold weather
- MIL on with the fault stored
- Slow warm-up in winter on vehicles where the fan also cools the low temperature circuit
- Fan motor becoming noisy over time from continuous running
Likely causes
- Relay contacts stuck or welded closed, which is the most frequent finding
- Control wire shorted to battery voltage in a chafed section of harness
- Internally shorted output driver inside the fan control module or the engine control module
- Water intrusion into the relay box or the fan control module
- Incorrect relay fitted during a previous repair, or a relay inserted in the wrong socket
- A temperature signal stuck high, which keeps the module commanding the fan on
- Damaged wiring after front end repair work bridging the fan feed to a permanent supply
How to fix it
- With the fan running and the ignition off, pull the fan relay; if the fan stops, the relay is stuck and the module is not at fault
- If the fan continues with the relay removed, look for a direct short feeding the motor
- Disconnect the control wire at the module and check whether battery voltage is present on it
- Inspect the harness for chafe damage where it passes across the front structure
- Check the relay box and any fan control module for water intrusion and corrosion
- Look at the temperature values the module is using; a sensor stuck at a high reading will keep the fan commanded on legitimately
- Replace the stuck relay or repair the short, then confirm the fan starts and stops on command