GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 TrailBlazer - 2WD 🢒 Engine 🢒 Engine Cooling 🢒 DTC P1484

Circuit Description

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 P1484 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.

Conditions for Running the DTC
    • 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 P1481 and P1482 are not set.
    • The engine speed is less than 3200 RPM.
    • The engine speed is not changing more than 250 RPM for 5 seconds.
    • Fan command is greater than 0%.

Conditions for Setting the DTC
    • The maximum allowable error of 1000 RPM in the cooling fan speed occurs for 100 seconds.
    • The PCM detects that the cooling fan clutch is locked up.

Action Taken When the DTC Sets
    • The Reduced Engine Power indicator illuminates only if the PCM detects that the cooling fan clutch is locked up.
    • 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%.

Conditions for Clearing the MIL/DTC

Important: Follow this procedure in order to clear DTC P1484 after completing a repair.

  1. Use the Clear DTC Information function on the scan tool.
  2. Perform an ignition key cycle.

The PCM turns OFF the MIL after the third consecutive trip that the diagnostic test has run and passed.

The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

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 in Wiring Systems.
    • Disconnect the harness connector of the cooling fan clutch from the shroud. Inspect the exposed wires between the harness connector and the tubing.
    • If DTCs P1484 and P0113 are set, and the weather conditions are cold, the cooling fan code may be false. Clear DTC P1484, and after an IAT sensor check, allow the DTC to reset .

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 clutch. The cooling fan clutch is completely disengaged when the excessive fan noise is not heard.

    4.

  4. Tests the PCM's ability to control the cooling fan. If answer to question is Yes, ensure to refer to all Diagnostic Aids.

    5.

  5. Inspect for a mechanical condition which causes the DTC to set.

    6.

  6. Tests for voltage on the cooling fan clutch supply voltage circuit of the cooling fan clutch. The cooling fan clutch connector is a seal connector. You must use jumper wires for testing or damage to wiring or connector could happen.

    7.

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

Step

Action

Values

Yes

No

Schematic Reference: Engine Cooling Schematics

Connector End View Reference: Cooling System Connector End Views

1

Did you perform the Engine Cooling Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Engine Cooling

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: DTC P1482, for 4.2l (LL8) 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 2000 RPM for 2 minutes.

Does the cooling fan engage?

--

Go to Step 4

Go to Step 5

4

Important: Continuously excessive fan noise is due to the PCM commanding the cooling fan to 100% 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 2000 RPM for 2 minutes.

Does the cooling fan clutch disengage?

--

Go to Step 5

Go to Step 18

5

  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the Fan Speed and the Desired Fan Speed parameters in the powertrain control module Output Controls.
  4. Command the cooling fan clutch to 100%.
  5. Operate the engine at 2000 RPM for 2 minutes.

Is the Desired Fan Speed within the specified speed of the Fan Speed?

1000 RPM

Go to Diagnostic Aids

Go to Step 6

6

  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 one of the following procedures:
    4. •  Drive Belt Excessive Wear Diagnosis in Engine Mechanical-4.2L
    •  Drive Belt Tensioner Diagnosis in Engine Mechanical-4.2L

Did you find and correct the condition?

--

Go to Step 20

Go to Step 7

7

  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 digital multimeter (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%.

Does the voltage measure greater than the specified value?

0.16 V

Go to Step 10

Go to Step 8

8

Command the fan control to 100%.

Does the voltage fluctuate?

--

Go to Step 11

Go to Step 9

9
  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 12

Go to Step 17

10

Disconnect the cooling fan relay.

Does the voltage measure greater than the specified value?

0.16 V

Go to Step 14

Go to Step 11

11

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

Did you find and correct the condition?

--

Go to Step 20

Go to Step 16

12

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

Did you find and correct the condition?

--

Go to Step 20

Go to Step 13

13

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 in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 15

14

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

Did you find and correct the condition?

--

Go to Step 20

--

15

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

Did you find and correct the condition?

--

Go to Step 20

Go to Step 19

16

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 in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 18

17

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

Did you find and correct the condition?

--

Go to Step 20

--

18

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

Did you complete the replacement?

--

Go to Step 20

--

19

Replace the cooling fan relay.

Did you complete the replacement?

--

Go to Step 20

--

20

Important: Follow this procedure in order to clear DTC P1484 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