GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 TrailBlazer - 2WD 🢒 Engine 🢒 Engine Cooling 🢒 DTC P1482

Circuit Description

The powertrain control module (PCM) sends a pulse width modulation (PWM) signal of 0-12 volts via the cooling fan clutch control circuit to the cooling fan relay. The PCM uses this PWM to control the position of the oil control valve located inside the cooling fan clutch. If during operation, the PCM detects an improper circuit condition on the cooling fan clutch control circuit DTC P1482 will set.

Conditions for Running the DTC

System voltage is greater than 8.5 volts.

Conditions for Setting the DTC
    • An improper voltage level has been detected on the cooling fan clutch control circuit.
    • The above condition is present for at least 6 seconds.

Action Taken When the DTC Sets
    • The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
    • The PCM stores the conditions present when the DTC sets as Freeze Frame/Failure Records data.
    • The PCM commands the cooling fan clutch to 100%.

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the malfunction indicator lamp (MIL) after the third consecutive trip the diagnostic has run and passed.
    • The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
    • The DTC can be cleared by using the scan tool Clear DTC Information function.

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.

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 for the ability of the PCM to control cooling fan clutch speed. If answer to question is Yes, ensure to refer to all Diagnostic Aids.

    5.

  5. Verifies the ignition 1 voltage circuit of the cooling fan relay.

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 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 17

5

  1. Install a scan tool.
  2. Start the engine.
  3. Observe the Fan Speed parameter in the powertrain control module Output Controls.
  4. With a scan tool, command the fan speed to increase.

Does the Fan Speed increase?

--

Go to Diagnostic Aids

Go to Step 6

6

  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 a good ground.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 11

7

Test the cooling fan clutch control circuit of the cooling fan relay for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 8

8

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

Did you find and correct the condition?

--

Go to Step 19

Go to Step 9

9
  1. Connect a test lamp to the cooling fan clutch control circuit of the cooling fan relay and ground.
  2. Connect a digital multimeter (DMM) to the test lamp probe and ground.
  3. Set the DMM to A/C range and select frequency.
  4. Start the engine.
  5. Verify that the Fan Control is commanded to 0%.

Is the frequency less than the specified value?

OL

Go to Step 14

Go to Step 10

10

Command the Fan Control to 100%.

Does the frequency fluctuate?

--

Go to Step 13

Go to Step 14

11

Inspect the Eng Fan fuse.

Is the fuse open?

--

Go to Step 12

Go to Step 15

12

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

Did you find and correct the condition?

--

Go to Step 19

Go to Step 15

13

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

Did you find and correct the condition?

--

Go to Step 19

Go to Step 16

14

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 18

15

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

Did you complete the repair?

--

Go to Step 19

--

16

Replace the cooling fan relay.

Did you complete the replacement?

--

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

Important: Perform the programming procedure for the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls-4.2L.

Did you complete the replacement?

--

Go to Step 19

--

19
  1. Use the scan tool in order to clear the DTCs .
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK