What does it mean?
Some vehicles are equipped with a sensor at the end of the cooling fan that detects movements during vehicle operation. The sensor is used to determine if the fan is operating on a vehicle equipped with a fan clutch or to verify that the fan speed commanded by the Powertrain Control Module (PCM) or Engine Control Module (ECM) matches the actual fan speed detected on an electric fan-equipped vehicle.
The sensor used is a 3-wire Hall effect sensor that uses a 5-volt reference source from the PCM, a ground wire, and a signal wire to the PCM to determine the fan speed. A P0528 means that the PCM/ECM has determined there is a fault with the sensor or the wiring.
Note: Be careful not to touch an electric fan, as it may turn on even when the vehicle is not running. This code is similar to P0526, P0527, and P0529.
Symptoms
Symptoms of a DTC P0528 may include:
• Illumination of the malfunction indicator lamp (also known as Check Engine Light)
• The vehicle may overheat or run hotter than normal
Causes
Potential causes of a P0528 code include:
• Faulty fan clutch or electric fan
• Open circuit in the cooling fan sensor harness or connector
• Faulty PCM/ECM
• Faulty cooling fan speed sensor
• Broken accessory belt
Possible Solutions
Fan Clutch Equipped – Visually check that the fan is spinning while the engine is running. If the fan is not spinning, it may be due to a broken accessory belt or a faulty fan clutch. Replace the accessory belt or fan clutch assembly.
Electric Fan Equipped – Visually check that the fan turns on and off when the PCM/ECM commands the fan to operate as the engine reaches certain temperatures. The fan may automatically activate when the air conditioning is turned on. If the fan does not operate, check the electrical harness connector, fuses, or relays that operate the electric fan. Some fans may be activated using an on/off relay or Pulse Width Modulation (PWM) for variable speed fans. Repair the electric fan circuit, replace the electric fan, fan motor, or control module.
Cooling Fan Sensor Harness – Check for loose connections and damaged wires that may have come into contact with the cooling fan. Disconnect the cooling fan sensor connector and the PCM connector, and check resistance using a Digital Volt-Ohm Meter (DVOM) with leads at each end of the signal wire. Some vehicle manufacturers have issued a Technical Service Bulletin (TSB) for replacing the sensor cable harness. Replace or repair the harness.
PCM/ECM – Disconnect the fan speed sensor harness and the PCM/ECM harness. Using a DVOM with positive and negative leads connected to each end, check for excessive resistance in the signal wire circuit. Back-probe the signal wire using a DVOM set to the volts scale or a graphing multimeter at the sensor harness and PCM/ECM, with the positive lead on the signal wire and the negative lead to a known good ground, to determine if voltage is present from the fan speed sensor. If the signal is present but not received by the PCM/ECM, replace the PCM/ECM.
Cooling Fan Speed Sensor – Disconnect the sensor harness connector and test continuity using a DVOM set to the Ohms scale between the power, ground, and signal wires. No resistance should be present between the signal wire and the ground or power wires. If resistance is present, there may be an internal short circuit.
The signal wire can only be tested during actual fan operation by probing the harness connector with the DVOM set to the volts scale or a graphing multimeter, with the positive lead on the signal wire and the negative lead to a known good ground. The Hall effect sensor used operates by creating a magnetic field that changes voltage as the fan spins. As the fan speed increases, the voltage should also increase. Replace the cooling fan speed sensor if a component failure is detected.