Fix code P0526 Cooling fan speed sensor circuit
GM has issued a service bulletin to address a P0526 Cooling fan speed sensor circuit trouble code on the following vehicles:
2002-04 Olds Bravadas
2002-05 Chevy TrailBlazers & TrailBlazer EXTs, GMC Envoys & Envoy XLs
2004-05 Buick Rainiers and GMC Envoy XUVs
2005 GMC Envoy Denalis & Envoy XL Denalis
The P0526 Cooling fan speed sensor circuit problem appears because of damaged wires in the cooling fan harness. The damage occurs because the harness pulls out of its plastic protective sleeve, exposing the insulation to the sharp edges of the sleeve. Replace the harness with an improved design (Part No. 89024920) and tape the wires to prevent movement within the sleeve. That’ll solve the problem. Here’s how to do it.
1) Remove the cooling fan assembly and place it on a workbench.
2) Disconnect the connector from the fan clutch and remove the harness from the plastic sleeve while feeding the wires out of the slot.
3) Wrap the area of the wires that will go into the sleeve with electrical tape. Make sure the tape is positioned at least 1 in. from the connector so the wires can be fed completely into the slot in the sleeve.
4) Next, push the wires through the slot and install the harness completely into the plastic sleeve. To complete the fix, reconnect the fan clutch electrical connector,
install the fan assembly, clear the DTC and check for proper fan operation.
©, 2013 Rick Muscoplat
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Error Code P0527 is defined as Fan Speed Sensor Circuit Range or Performance Issue. This means there’s range or performance problem on the fan speed sensor circuit, likely caused by a defective temperature sensor or damaged wires.
This code is a generic trouble code, meaning it applies to all cars 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 cars come with a special sensor called cooling fan speed sensor to detect movement during the operation of your 2004 GMC Envoy . 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 2004 GMC Envoy .
This sensor has three wires that use a 5V reference source coming from the PCM, a ground wire, and a signal wire to the PCM to read the fan speed.
This code is triggered when the PCM detects that the actual fan speed doesn’t match with the commanded or desired speed.
Other related electric fan error codes include:
- Error Code P0526
- 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 your 2004 GMC Envoy ’s memory system. Other common symptoms include:
- Overheating
- Vehicle running hotter than usual
- A/C not working
Possible Causes
There are many reasons for the clutch or electric fan to not run at commanded or desired speed, such as:
- Defective cooling fan motor
- Defective cooling fan relay
- Defective engine coolant temperature sensor
- Broken, frayed, or shorted wires at the engine coolant temperature sensor
- Broken, frayed, or shorted wires at the fan speed sensor
- Corroded, damaged, or loose connectors at the engine coolant temperature sensor
- Corroded, damaged, or loose connectors at the fan speed sensor
- Defective electric fan
- Defective fan clutch
- Defective fan speed sensor
- Blown fuse
How to Check
As with most codes, the first step for diagnosis for this would be to check if there are other codes present in the PCM as well. These codes should be addressed in the order that they appear. Collect these trouble codes and record their freeze frame data.
Next, check the cooling fan assembly and look for signs of damages in wires, such as broken, frayed, or shorted wires. Repair or replace as necessary. The same goes for the cooling fan assembly connectors – look for signs of damage, corrosion, and bent pins.
Next, check the relay and fuses of the fan motor. Repair or replace as necessary.
Then, clear the codes and test drive your 2004 GMC Envoy to see if the code comes back.
If the code comes back, check the engine coolant temperature sensor for breakage, frayed, or shorts in the wiring. Repair or replace as necessary. Do the same for the connectors of the engine coolant temperature sensor – look for bent pins, corrosion, or damages, and do the necessary repair or replacement.
Then, clear the codes and take your 2004 GMC Envoy for a test drive again. If the code comes back, and your 2004 GMC Envoy has a high or low-pressure switch for the A/C or fan, then check it for proper operation. Replace this component as necessary.
Clear the code and take your 2004 GMC Envoy for a test drive. If the code comes back again, then it’s time to look at the PCM. Make sure there’s proper wiring.
How to Fix
Depending on the diagnosis, common repairs for this code include:
- Replacement of engine coolant temperature sensor
- Repair or replacement of wiring issues in engine coolant temperature sensor
- Repair or replacement of wiring connector issues in engine coolant temperature sensor
- Replacement of fan speed sensor’s wiring issues
- Replacement of fan speed sensor connector issues
- Replacement of cooling fan relay
- Replacement of cooling fan motor
- Replacement of electric fan
- Replacement of fan clutch
- Replacement of blown fuse
- Replacement of fan speed sensor
The most common mistake in addressing this code is replacing the cooling fan assembly when the problem is only at the wiring, bad fuse, or defective relay. Thus, it pays to check thoroughly to avoid unnecessary and expensive replacements.
Also, it is rare for the PCM to go bad, but it is possible.