Error Code P0526 is defined as Cooling Fan Speed Sensor Circuit. This code is a generic trouble code, which means it appears in all vehicles equipped with the OBD-II system, particularly 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 a 5V reference source coming from the PCM, a ground wire, and signal wire to the PCM to read the fan speed. When Error Code P0526 is detected, that means the PCM has determined a problem in the sensor or the wiring.

Other related error codes include:

  • Error Code P0527
  • Error Code P0528
  • Error Code P0529

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:

  • Vehicle overheating or running hotter than usual
  • AC not working properly

Possible Causes

In most cases, this code is caused by a defective cooling fan motor. Other possible causes include:

  • Defective cooling fan relay
  • Defective engine coolant temperature sensor
  • Corroded or loose electrical components
  • Defective cooling fan
  • Open or shorted electrical wiring, which may lead to a blown fuse

How to Check

Note: Make sure you don’t touch the electric fan, as it may turn on when the vehicle is operating.

For Fan Clutch Equipped

Make sure the fan is spinning correctly while the engine is running. If it’s not, then it may be caused by failed clutch assembly or, broken accessory belt. Replace as necessary.

For Electrical Fan Equipped

Check whether the fan is turning on and off when the PCM commands the fan to run when the engine reaches a certain temperature. In many cases, the fan may be automatically activated when the AC is turned on. If the fan is not running, check the electrical harness, fuses, or relays that operate the electric fan. Some fans may be turned on using an on/off relay or activated by the PVM (pulse width modulation), with variable speed fans. Replace electric fan assembly, electrical fan circuit, motor or fan module, if equipped.

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 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 for this code include:

  • Replacement of defective cooling fan relay
  • Replacement of defective cooling fan motor
  • Repair or replacement of corroded or loose electrical components
  • Replacement of defective engine coolant temperature sensor
  • Repair or replacement of open or shorted electrical wiring (if this problem leads to a blown fuse, then you would have to replace the fuses too)
  • Replacement of the defective cooling fan

When dealing with this code, like most codes, it’s important 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.