What it means
The control module monitors the charge-air-cooler fan control driver while commanding fan operation. It sets this code when the driver does not perform as expected; the code alone does not identify the failed component.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The module's fan control driver switches or regulates the CAC fan when cooling is needed. P028F sets when the driver does not behave as expected during a fan command; the code alone does not identify whether the driver, fan, wiring, or its power and ground connections are at fault.
Common causes
Most likely first.
- Fault in fan control driver or module
- Fan motor drawing excessive current
- Fan wiring or connector fault
- Poor power or ground connection
Symptoms
- Check-engine light
- Reduced engine power
- Higher intake-air temperature
- Possible engine protection warning
How to diagnose it
- Use a scan tool to review freeze-frame data and compare the CAC fan command with fan response and intake-air temperature.
- Inspect the CAC fan, its connector, and nearby wiring for damage, loose terminals, or signs of overheating.
- Check the fan's power and ground connections for secure contact and voltage drop using the manufacturer's procedure.
- Measure fan current during a commanded operation and compare it with the manufacturer's specification to identify excessive draw.
- If the fan and its wiring test correctly, test the control driver's output and module connections according to the manufacturer's procedure.
Common fixes
- Repair loose or damaged fan wiring and connector terminals.
- Restore poor fan power or ground connections.
- Replace a CAC fan motor that draws excessive current or fails the specified test.
- Repair the fan control driver or module if testing isolates the fault there.
Can I keep driving?
The CAC fan may not cool intake air reliably, and the engine may reduce power or display an engine-protection warning. Avoid heavy loads and stop if that warning appears or power falls noticeably.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.