Error Code P0529 is defined as Fan Speed Sensor Circuit Intermittent. This means the cooling fan is sending an incorrect voltage signal, a problem caused by corroded, open, or shorted wiring or damaged fan motor, relay, or speed sensor.


This code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.

Some vehicles come with a special sensor called cooling fan speed sensor to detect movement during the operation of the vehicle. This sensor determines the fan clutch or verifies the fan speed as commanded by the PCM (powertrain control module, also known as the ECM or engine control module), to match the actual fan speed detected on an electric fan equipped vehicle.

This sensor has three wires that use 5V reference source coming from the PCM, a ground wire, and signal wire to the PCM to read the fan speed.

When this code is triggered, that means the PCM has not received a voltage output from the fan sensor signal wire.

Other related codes include:

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other common symptoms include:

  • Overheating
  • Vehicle running hotter than usual
  • A/C not working properly

Possible Causes

Several problems could lead to this code, such as:

  • Faulty, open, or shorted wiring
  • Faulty cooling fan motor
  • Faulty cooling fan relay
  • Faulty cooling fan speed sensor
  • Faulty, corroded or loose electrical connectors
  • Defective engine coolant temperature sensor
  • Damaged or defective PCM (rare)

How To Check

For Cooling Fan Sensor Harness

Check the wiring and connectors that may have come in contact with the cooling fan. Look for signs of damages. Unplug the cooling fan sensor connector and the connector at the PCM. Use your DVOM (digital volt ohm meter) to check for resistance. Use leads at each end of the power wire, signal wire, and ground (if connected to the PCM). Some manufacturers provide TSB (technical service bulletin for the proper procedure of sensor wiring harness replacement. Repair or replace harness as necessary.

To Check the PCM

With KOEO (key on engine off) unplug the harness connector at the cooling fan sensor and then check for 5V reference source from the PCM. Set the DVOM at volts scale and use the wiring diagram for reference; place positive lead on the power wire and negative lead to a known good ground. Then, use the DVOM’s positive lead connected to a known good power source to check for ground and the negative lead at harness ground wire. If no reference voltage is being supplied, then it’s time to replace the PCM.

To Check the Cooling Fan Speed Sensor

Disconnect the harness connector from the sensor and then use the DVOM set at ohms to test for continuity between the ground and power wires. There should be resistance between the two wires.

Testing Signal Wire

The signal wire must only be tested during actual fan operation through back probing of the harness connector using DVOM set at volts or with the use of graphic multimeter with positive lead on the signal wire and negative lead to a known ground.

As the speed of the fan increases, the voltage must also increase. Thus, it’s good to monitor the fan speed using an advanced scan tool to verify if the actual fan speed matches the commanded fan speed. If the cooling fan speed sensor fails, then it must be replaced.

How To Fix

Depending on your diagnosis, common repairs include:

  • Repair or replacement of corroded, damaged, loose, or shorted connectors and wirings
  • Replacement of defective engine coolant temperature sensor
  • Replacement of defective cooling fan speed sensor
  • Repair or replacement of faulty engine cooling fan motor
  • Repair or replacement of faulty engine cooling fan relay
  • Replacement of damaged PCM (rare)

As with most codes, it’s imperative to always clear the code from the PCM and retesting the system before moving on to another step of the repair. This will allow you to narrow down and pinpoint exactly what went wrong and ensure you make unnecessary replacements.