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DTC codes / P02xx · Fuel and air metering (injector circuits) / P028B

P028BCharge Air Cooler Cooling Fan Performance/Stuck Off

P028B indicates that the powertrain control module (PCM) has detected a performance fault in the charge air cooler (CAC) cooling fan circuit, specifically that the fan is not responding or is stuck in the off position when commanded on. The PCM monitors the fan circuit and expects feedback, such as current draw or a diagnostic signal, to confirm the fan is operating; when that feedback is missing or out of range, the code is set.

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

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms.
  • Reduced engine power or limp mode under heavy load or high ambient temperatures.
  • Increased intake air temperatures, potentially leading to derating or overheating.
  • Poor fuel economy or reduced performance during sustained driving.
  • In rare cases, the engine may enter a protection strategy that limits boost or RPM.

Common causes, most likely first

  1. Failed charge air cooler cooling fan motor (open winding or seized bearing).
  2. Blown fuse or faulty relay in the fan power circuit.
  3. Damaged or corroded wiring harness or connector at the fan or PCM.
  4. Faulty intake air temperature (IAT) sensor or charge air temperature sensor providing incorrect data.
  5. PCM software issue or internal driver fault (less common).
  6. Restricted or blocked charge air cooler fins reducing airflow and causing the fan to overwork or fail.
  7. Poor ground connection for the fan circuit.

How to diagnose and fix it

  1. Verify the code with a scan tool and check for related codes in other modules.
  2. Inspect the fan fuse and relay, and test the relay operation with a multimeter.
  3. Visually inspect the fan connector and wiring for damage, corrosion, or loose pins.
  4. Command the fan on using a scan tool bidirectional control and listen for fan operation; if no response, check for power and ground at the fan connector.
  5. Test the fan motor directly by applying battery voltage to confirm it spins; replace if seized or open.
  6. Check the intake air temperature sensor readings for plausibility and compare with ambient temperature after a cold soak.
  7. If all electrical components test good, check for PCM software updates or consult a dealer for advanced diagnostics.

Don't overlook the charge air cooler fan relay

  • A stuck-open fan relay is a frequent cause that is often missed because the fan motor itself tests good when powered directly.
  • The PCM may set P028B even if the fan runs intermittently, so a fan that works during a quick test can still be the culprit under load.
  • Corrosion inside the fan connector can cause high resistance that prevents the fan from starting, yet the connector may look fine from the outside.
  • On some vehicles, the charge air cooler fan shares a circuit with the radiator fan, so a fault in the shared relay or fuse can trigger this code along with others.
  • A restricted charge air cooler can cause the fan to run constantly and eventually fail, so always check for debris or bent fins.

Can I keep driving with P028B?

You can usually drive with this code, but avoid heavy loads, towing, or sustained high-speed driving until repaired, as the engine may enter a power-reduction strategy to protect itself from high intake air temperatures.

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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