DTC P0528 – Engine Coolant Blower Motor Speed Sensor No Signal

By Benjamin Jerew (Contact Me)
Last Updated 2020-06-05
ASE Master Tech

Trouble CodeFault LocationProbable Cause
P0528 Engine coolant blower motor speed sensor no signal Wiring, poor connection, blower motor speed sensor, ECM

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What Does Code P0528 Mean?

Much of the internal combustion engine’s power is lost as heat. For best performance, the engine needs to operate within a specific temperature range. Too cold, and the fuel does not vaporize as efficiently. Too hot, and the fuel vaporizes too quickly. Either situation can cause performance problems and possible engine damage. The engine cooling system is basically a coolant circuit between the engine and radiator, transferring a portion of combustion heat to the atmosphere. Additional coolant circuits may include the heater core, for cabin heating, and the automatic transmission, to modulate automatic transmission fluid temperature.

When the vehicle is cruising, usually above 35 mph, enough airflow is present through the radiator for efficient heat transfer. On the other hand, below 35 mph or when the air conditioner is running, more airflow is required. This additional airflow is provided by one or more fans, powered by drive belts or electric motors. On some vehicles, the engine control module (ECM) monitors fan speed. This can be to confirm the fan is operating or to modulate variable-speed fans. If the ECM cannot detect a fan speed sensor (FSS) signal, it cannot determine fan operation or speed. In this case, it will illuminate the check engine light (CEL) and set a diagnostic trouble code (DTC). If there is no FSS signal, DTC P0528 is defined as “Engine Coolant Blower Motor Speed Sensor No Signal” or “FSS No Signal.”

Where is the P0528 sensor located?

The FSS is located on the fan driver, which may be an electric motor or a clutch. Electric motor FSS usually use the same circuits as the motor, so there is not a separate sensor. For belt-driven fans, whether equipped with electronic, speed, or temperature clutch, the FSS is located on the fan shaft, usually part of the clutch assembly. This type of FSS may be in front of or behind the fan.

The FSS is a Hall Effect sensor, generating a digital on-off signal, the frequency of which the ECM uses to calculate fan speed.

What are the common causes of code P0528 ?

Depending on year, make, and model, DTC P0528 may have number of causes. Here are some of the most common.

  • Fan Driver – Whether driven by an electric motor or clutch, if this fails, the fan will not be driven at all, meaning even if the FSS is functional, it will have nothing to transmit.
  • Fan Motor Relay or Module – Similarly, if the fan motor relay or module fails, it cannot drive the electric fan.
  • Fan Speed Sensor – If the FSS fails, it will not send a fan speed signal to the ECM.
  • Wiring – In the case of wiring routed close to the fan, especially where the clutch and FSS are mounted in front of the fan, fan abrasion can lead to an open circuit in the FSS or clutch circuits.
  • Engine Coolant Temperature (ECT) – Some electric fans are controlled by an ECT. If this sensor is faulty, the fan driver will not be commanded when the ECM expects. Concurrent ECT DTCs will likely be present.
  • Drive Belt – On clutch driven fans, a slipping or broken drive belt will not drive the fan properly, if at all, so the FSS will have nothing to report. Other problems, such as alternator or power steering issues, may be present at the same time.

How expensive is it to fix code P0528 ?

Diagnosis should take an hour or less, judging by the few sensors and actuators involved. Electrical repairs are straightforward. Because the FSS is usually integrated into the fan motor or fan clutch, it may seem expensive to replace the whole thing when only the FSS has failed. Chances are good that, if the FSS has failed, its accompanying motor or clutch probably is not far behind, making this a good combination.

What are the symptoms of code P0528 ?

  • MIL / CEL – In some situations, the only indication you will have is an illuminated CEL.
  • Overheating – If the fan is disabled because the ECM or fan controller cannot see an FSS signal, then engine or transmission will overheat driving below about 35 mph or with the air conditioning engaged.
  • Fan Always On – Depending on failure mode, the ECM may simply command the fans to run full speed, disregarding typical fan control inputs. You will notice much more noise from the engine bay.
  • Poor AC or No AC – Depending on failure mode, you may experience poor air conditioning performance. If the engine is overheating because the fan is inoperative, the condenser will operate at lower efficiency. In some cases, the ECM will disable AC function to prevent engine overheating.

What are common solutions to code P0528 ?

The most common fixes for this DTC follow the most common problems. The most common problem is a failed FSS, which requires replacing the fan clutch assembly. Second to this is wiring damage because of fan abrasion, typical for vehicles where there FSS is mounted forward of the fan. Otherwise, typical electrical fixes apply, such as fuse, relay, or motor replacement.

How serious is code P0528 ?

There is typically no danger to running the vehicle if the fan is turning on, even if the ECM cannot detect an FSS signal. If the fan runs all the time as part of a fault mode, this may stress the electrical system, as it is typically meant to run only intermittently. On the other hand, if the fan is disabled because its driver is faulty (bad belt, bad clutch, bad relay, broken circuit, etc.), the car will run but start to overheat. If the engine overheats, this can cause permanent damage to the engine, possibly the automatic transmission as well.

How safe is it to still drive the car with code P0528 ?

Aside from possible damage, you should have no issues maintaining safe control of your vehicle if the FSS signal is missing.

How difficult is it to repair code P0528 ?

Most DIY mechanics should have no problems replacing the parts involved, such as fan clutch, electric fan motor, or fan relay. Electrical repairs are limited to basic wiring, but be sure to use marine shrink wrap to properly seal any repairs from moisture.

What are the common mistakes when repairing code P0528 ?

Some people jump to replacing fan clutch and FSS assembly “because it is an FSS code” without testing rest of circuit. For example, a slipping fan clutch will not drive the fan, resulting in a missing FSS signal. Similarly, a faulty fan relay or fuse will prevent fan activation and the generation of an FSS signal. Replacing the fan clutch or electric fan motor will not solve the problem. Be sure to test all parts of the fan control circuit and FSS circuit before condemning any one part.

How do you troubleshoot code P0528 ?

First, confirm fan operation. For electric fans, check fuses, relays, and circuits. For belt-driven fans, check the clutch for play and that the belt is intact and not slipping.

The best way to diagnose the FSS signal is to backprobe the FSS connector with a graphing meter to view the digital on-off signal, which should switch between 0 V and 5 V when the engine is running. Barring this, you may be able to view the same with the engine not running and turning the fan slowly by hand and looking for a sudden switching between 0 V to 5 V on a digital multimeter set to the VDC scale. Use the electrical wiring diagram specific to your vehicle to determine which circuit to test. Check the FSS has proper power and ground, as well.

Codes Related to P0528

P0526

P0527

P0529

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