Fan control relay or driver stuck in the closed (on) position; Wiring fault, such as a short to battery positive or to the control wire, on the fan control circuit; Faulty fan motor or integrated fan control module that runs without a valid command; Corroded or damaged connector causing a false feedback signal or unwanted fan activation; Faulty intake air or charge air temperature sensor giving a misleading reading that keeps the fan demanded; Fault inside the engine control unit output stage, or an outdated calibration that is a known cause on some models.

P028C

Charge Air Cooler Cooling Fan Stuck On.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
2: AreaFuel and air metering (injector circuit)
8C: FaultThe specific fault in that area

What it means

P028C means the engine control unit has detected that the charge air cooler cooling fan is running when it has not been commanded to, or is not responding to a command to switch off. The charge air cooler cools the compressed intake air from the turbocharger or supercharger. The control unit compares the fan command with the fan's feedback or its effect on intake air temperature, and sets the code when they do not agree. How the fan is controlled and monitored depends on the model and engine.

Symptoms

Charge air cooler fan running constantly, even with the engine cold or after switch-off
Engine warning light on
Fan noise or battery drain after the ignition is off
Slightly lower intake air temperatures than expected, or reduced warm-up performance in cold weather
Possible loss of power if the control unit enters a protective mode
Flat battery after the car has been left standing

Possible causes

Fan control relay or driver stuck in the closed (on) positionlikely
Wiring fault, such as a short to battery positive or to the control wire, on the fan control circuitlikely
Faulty fan motor or integrated fan control module that runs without a valid commandpossible
Corroded or damaged connector causing a false feedback signal or unwanted fan activationpossible
Faulty intake air or charge air temperature sensor giving a misleading reading that keeps the fan demandedpossible
Fault inside the engine control unit output stage, or an outdated calibration that is a known cause on some modelsrare

How to diagnose

Read all stored and pending codes and record the freeze frame data, noting engine temperature, intake air temperature and vehicle speed when the code set.
Check for related codes covering the fan circuit, temperature sensors or the cooling system, and check for any manufacturer bulletins for the model and engine.
With the ignition off, listen and look to see whether the charge air cooler fan is still running, and inspect the fuse and relay for the fan circuit.
Inspect the fan wiring and connectors for chafing, heat damage, water ingress and corrosion, and check for shorts to battery positive.
Using the live data, compare the commanded fan state with the actual fan operation and check the charge air and intake air temperature readings are plausible.
Swap the fan relay with a known good identical relay, where fitted, and see whether the fan behaviour changes.
Command the fan on and off with a bidirectional scan tool, and check the supply, earth and control signals at the fan connector using the wiring diagram for that model.
If the circuit and fan test correctly, check for a software update for the control unit before considering a control unit fault.

How to fix

Replace a faulty or stuck fan control relay.
Repair or replace damaged wiring, and clean or replace corroded connectors on the fan circuit.
Replace the fan motor or fan control module if it runs without a valid command.
Replace a faulty intake air or charge air temperature sensor if it is giving a false reading.
Update the control unit calibration if the manufacturer lists an outdated calibration as a cause, or repair or replace the control unit if it is confirmed faulty.

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair, as a fan that is stuck on does not usually cause immediate engine damage. Get it checked soon, because a fan that runs constantly can flatten the battery and may overheat the fan motor or wiring.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.