P0493

DTC P0483 or P0493
Circuit Description
The following DTC's are for the cooling fan clutch:
^ P0483 is for the difference of the commanded cooling fan speed compared to actual cooling fan speed is greater than 1,000 RPM.
^ P0493 is for a cooling fan clutch overspeed condition, approximately 6,800 RPM.
The cooling fan relay sends a pulse width modulation (PWM) signal of 12 - 14 volts to the cooling fan clutch through the cooling fan clutch supply voltage circuit. The powertrain control module (PCM) uses this PWM signal in order to control the speed of the cooling fan clutch. The signal controls the position of the oil control valve inside the cooling fan clutch. If the cooling fan RPM is different than the PCM is expecting, DTC P0483 will set. The actual cooling fan RPM vs the desired cooling fan RPM is not always exactly the same. There can be up to an 800 RPM difference. If the PCM detects that the cooling fan speed is over 6,800 RPM then DTC P0493 will set.

DTC Descriptors
This diagnostic procedure supports the following DTC's:
^ DTC P0483 Cooling Fan System Performance
^ DTC P0493 Cooling Fan Overspeed

Conditions for Running the DTC
DTC P0483
^ The engine is running.
^ The system voltage is greater than 8.5 volts.
^ The intake air temperature (IAT) is greater than -7°C (19°F).
^ DTC's P0480 and P0526 are not set.
^ The engine speed is less than 3,200 RPM.
^ The engine speed is not changing more than 250 RPM for 5 seconds.
^ Fan command is greater than 0 percent.

DTC P0493
The engine is running.

Conditions for Setting the DTC
DTC P0483
The difference between commanded and actual cooling fan speed is greater than 1,000 RPM for 100 seconds.

DTC P0493
The cooling fan RPM is greater than 6,800 RPM.

Action Taken When the DTC Sets
DTC P0483
^ The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
^ The PCM will store the conditions as Freeze Frame/Failure Records data.
^ The PCM commands the cooling fan clutch to 100 percent.

DTC P0493
^ The Reduced Engine Power indicator illuminates.
^ The PCM will store the conditions as Freeze Frame/Failure Records data.

Conditions for Clearing the MIL/DTC
The PCM turns OFF the MIL after the third consecutive trip that the diagnostic test has run and passed.

Diagnostic Aids
^ An inline connector could cause an intermittent DTC. Ensure to test for poor connections and pin retention at all inline connectors. Refer to system schematics for connector and locations.
^ If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections.
^ Disconnect the harness connector of the cooling fan clutch from the shroud. Inspect the exposed wires between the harness connector and the tubing.

Test Description

Steps 1-5:

Steps 6-16:

Steps 17-20:

The numbers below refer to the step numbers on the diagnostic table.
2. This step ensures that the DTC has failed this ignition cycle. If the scan tool displays Passed, then the answer is No.
3. The cooling fan noise should increase as the cooling fan clutch engages. It can take up to 2 minutes for full cooling fan clutch engagement. If cooling fan clutch is previously fully engaged, then there will not be a noticeable change in cooling fan noise. Compare noise to a known good vehicle. If fan noise is louder than the known good vehicle, then answer Yes.
4. In the previous step the cooling fan clutch was fully engaged. This step tests to ensure that the cooling fan clutch will disengage. A noticeable noise difference should be heard between a fully engaged cooling fan clutch and a disengaged cooling fan. The cooling fan clutch is completely disengaged when the excessive fan noise is not heard.
5. This step tests the PCM's ability to control the cooling fan clutch. If answer to question is Yes, ensure to refer to all Diagnostic Aids.
6. This step inspects for a mechanical condition which causes the DTC to set.
7. This step tests for voltage on the cooling fan clutch supply voltage circuit of the cooling fan clutch. The cooling fan connector is a seal connector. You must use jumper wires for testing or damage to wiring or connector could happen.
8. This step tests the cooling fan relay for a PWM signal on the cooling fan clutch supply voltage circuit of the cooling fan.