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DTC codes / P02xx · Fuel and air metering (injector circuits) / P028C

P028CCharge Air Cooler Cooling Fan Stuck On

P028C indicates that the powertrain control module (PCM) has commanded the charge air cooler (CAC) cooling fan on, but the fan's feedback circuit reports that the fan remains powered or spinning when it should be off. In plain terms, the computer sees the fan stuck running when it has asked it to stop, which can drain the battery or over-cool the intake charge.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • The cooling fan for the charge air cooler continues to run after the engine is shut off, often until the battery is drained.
  • A constant fan noise from the engine bay even when the engine is cold or the key is off.
  • The check engine light illuminates, sometimes accompanied by a message on the driver information center.
  • In some cases, no symptoms besides the warning light, especially if the fan only sticks intermittently.
  • Possible reduction in engine performance or fuel economy if the fan runs continuously and overcools the charge air, though this is less common.
  • Battery drain leading to a no-start condition if the fan runs for extended periods with the engine off.

Common causes, most likely first

  1. A failed charge air cooler fan relay that has welded its internal contacts closed, keeping power applied to the fan.
  2. A short to power in the fan control circuit wiring, often due to chafed insulation or a pinched harness.
  3. A faulty fan control module or integrated relay inside the fan assembly that fails in the on state.
  4. A stuck fan motor that continues to run whenever power is present, regardless of command.
  5. Corrosion or water intrusion in the fan connector or relay socket causing a permanent power feed.
  6. A PCM software glitch or internal driver failure that keeps the fan output energized, though this is rare.
  7. Aftermarket accessories or improper wiring repairs that backfeed power into the fan circuit.

How to diagnose and fix it

  1. Verify the fan operation by commanding the CAC fan on and off with a scan tool and observing whether the fan responds correctly or stays running.
  2. Inspect the fan relay and swap it with an identical relay from a non-critical circuit to see if the stuck-on condition moves with the relay.
  3. Disconnect the fan connector and check for power and ground on the control circuit with the key off; if power is present, trace the circuit for a short to power.
  4. Check the fan motor by applying power and ground directly to the fan terminals to confirm it runs only when powered and stops when power is removed.
  5. Inspect the wiring harness from the relay to the fan for chafing, corrosion, or pinched sections, especially near heat sources and moving components.
  6. Test the PCM output driver if all other components check out, looking for a shorted driver or software issue that keeps the fan command on.
  7. After repairs, clear the code and perform a road test with several key cycles to confirm the fan cycles correctly and the code does not return.

Relay failures that mimic a stuck fan

  • A welded relay contact is the most common cause of this code, yet many technicians replace the fan motor first because the fan is what they hear running.
  • The fan may only stick on intermittently, so a cold engine and a key-off test are essential; a quick visual check with the engine running can miss the fault entirely.
  • Some vehicles use a pulse-width-modulated (PWM) fan controller that can fail in the full-on state, and the controller is often integrated into the fan assembly, making it a costly misdiagnosis if the relay is overlooked.
  • A short to power in the fan circuit can be caused by aftermarket alarm or remote start wiring that taps into the wrong circuit, so always check for non-factory modifications.
  • The code can set if the fan runs for a few seconds after key-off as part of a normal cool-down strategy on some vehicles, so consult the specific model's strategy before condemning parts.

Can I keep driving with P028C?

You can usually drive the vehicle short distances to a repair shop, but avoid leaving it parked for long periods because the fan may drain the battery and leave you stranded. If the fan runs continuously with the engine off, disconnect the battery negative terminal when parked until the fault is repaired.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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