GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 TrailBlazer - 2WD 🢒 Accessories 🢒 Navigation Systems 🢒 DTC P0483 or P0493

Circuit Description

The following DTCs 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 DTCs:

    • 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).
    • DTCs 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

The numbers below refer to the step numbers on the diagnostic table.

  1. This step ensures that the DTC has failed this ignition cycle. If the scan tool displays Passed, then the answer is No.

    2.

  2. 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.

  3. 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.

    4.

  4. 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.

    5.

  5. This step inspects for a mechanical condition which causes the DTC to set.

    6.

  6. 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.

    7.

  7. This step tests the cooling fan relay for a PWM signal on the cooling fan clutch supply voltage circuit of the cooling fan.

Step

Action

Values

Yes

No

Schematic Reference: Engine Cooling Schematics

Connector End View Reference: Cooling System Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. With a scan tool, observe the Powertrain DTC list.
  2. Start the engine.
  3. Operate the vehicle within the Conditions for Running in the DTC.

Does the scan tool indicate the DTC Failed this ignition cycle?

--

Go to Step 5

Go to Step 3

3

Important:  P0480, for 5.3L (LM4), will set when the cooling fan relay is disconnected.

  1. Turn OFF the ignition.
  2. Disconnect the coolant fan relay.
  3. Connect a 10-amp fused jumper wire between the cooling fan clutch supply voltage circuit of the cooling fan and the ignition 3 voltage circuit of the cooling fan relay.
  4. Start the engine.
  5. Raise engine speed to 2,000 RPM for 2 minutes.

Does the cooling fan clutch engage?

--

Go to Step 4

Go to Step 5

4

Important: Continuously excessive fan noise is due to the powertrain control module (PCM) commanding the cooling fan clutch to 100 percent engaged or a mechanical failure. If the fan noise decreases during this step, then this DTC is due to an electrical malfunction. Replacing the cooling fan clutch will not correct the condition.

  1. Turn OFF the ignition.
  2. Remove the 10-amp fused jumper wire.
  3. Install cooling fan relay.
  4. Disconnect the cooling fan clutch connector.
  5. Start the engine.
  6. Raise engine speed to 2,000 RPM for 2 minutes.

Does the cooling fan clutch disengage?

--

Go to Step 5

Go to Step 17

5

  1. Turn OFF the ignition.
  2. Inspect the cooling fan and the drive belt for the following conditions:
    3. • A cracked drive belt
    • A loose or a worn drive belt
    • A misrouted drive belt
    • Oil leaks at the cooling fan clutch
    • A free-spinning cooling fan
    • A seized cooling fan clutch
    • A broken cooling fan
  3. If the above conditions exist, refer to Cooling Fan and Shroud Replacement .

Did you find and correct the condition?

--

Go to Step 19

Go to Step 6

6

  1. Disconnect the cooling fan clutch connector at the fan shroud.
  2. Connect a jumper wire between each of the cooling fan clutch circuits.
  3. Connect a DMM between the clutch supply voltage circuit of the cooling fan clutch and ground.
  4. Start the engine.
  5. Command the Fan Control to 0 percent.

Does the voltage measure greater than the specified value?

0.16 V

Go to Step 9

Go to Step 7

7

Command the Fan Control to 100 percent.

Does the voltage fluctuate?

--

Go to Step 10

Go to Step 8

8

  1. Turn OFF the ignition.
  2. Disconnect the cooling fan relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition 1 voltage circuit of the cooling fan relay with a test lamp connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 16

9

Disconnect the cooling fan relay.

Does the voltage measure greater than the specified value?

0.16 V

Go to Step 13

Go to Step 10

10

Test the cooling fan ground for an open. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 19

Go to Step 15

11

Test the ground circuit of the cooling fan relay for an open or a high resistance. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 19

Go to Step 12

12

Test the clutch supply voltage circuit of the cooling fan clutch for an open or a short to ground. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 19

Go to Step 14

13

Test the clutch supply voltage circuit of the cooling fan clutch for a short to voltage. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 19

--

14

Inspect for poor connections at the cooling fan relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs .

Did you find and correct the condition?

--

Go to Step 19

Go to Step 18

15

Inspect for poor connections at the harness connector of the cooling fan clutch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs .

Did you find and correct the condition?

--

Go to Step 19

Go to Step 17

16

Repair the ignition 1 voltage circuit of the cooling fan relay. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 19

--

17

Replace the cooling fan clutch. Refer to Fan Clutch Replacement .

Did you complete the replacement?

--

Go to Step 19

--

18

Replace the cooling fan relay.

Did you complete the replacement?

--

Go to Step 19

--

19

Important: Follow this procedure in order to clear DTC P0483 or DTC P0493 after making a repair.

  1. Use the Clear DTC Information function of the scan tool.
  2. Perform an ignition key cycle.
  3. Operate the vehicle within the Conditions for Running in the DTC.

Does the DTC reset?

--

Go to Step 2

System OK