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DTC P1481: Test

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Engine Cooling Diagnostic System Check? If so, go to next step. If not, go to DIAGNOSTIC SYSTEM CHECK - ENGINE COOLING  under SELF-DIAGNOSTIC SYSTEM.
  2. Install a scan tool. Start the engine. With the scan tool, observe the Fan Speed parameter in the PCM ENG 3 data list. Does the scan tool indicate that the Fan Speed parameter is 550-800 RPM? If so, go to DIAGNOSTIC AIDS  . If not, go to next step.
  3. Turn OFF the ignition. Disconnect the cooling fan clutch harness connector at the shroud. Connect a jumper wire between each of the following circuits:
    • The 5-volt reference circuit.
    • The cooling fan speed signal circuit.
    • The low reference circuit.

    Connect a digital multimeter (DMM) to the cooling fan speed signal circuit and ground. Turn ON the ignition with the engine OFF. Manually rotate the cooling fan. Does the DMM voltage change from 0-5 volts? If so, go to step  10 . If not, go to next step.

  4. Disconnect the jumper wires. Measure the voltage between the 5-volt reference circuit and the low reference circuit of the cooling fan. Is the voltage measurement about 5 volts? If so, go to next step. If not, go to step  7 .
  5. Turn OFF the ignition. Probe the low reference circuit of the cooling fan clutch with a test lamp connected to battery positive voltage. Does the test lamp illuminate? If so, go to next step. If not, go to step  9 .
  6. Test the 5-volt reference circuit of the cooling fan clutch for a high resistance, or for an open. Did you find and correct the condition? If so, go to step  15 . If not, go to next step.
  7. Test the cooling fan speed signal circuit of the cooling fan clutch for a short to ground, for a high resistance, or for an open. Did you find and correct the condition? If so, go to step  15 . If not, go to next step.
  8. Test the cooling fan speed signal circuit of the cooling fan clutch for a short to voltage. Did you find and correct the condition? If so, go to step  15 . If not, go to step  11 .
  9. Disconnect the PCM. Test the low reference circuit of the cooling fan for a high resistance or for an open. Did you find and correct the condition? If so, go to step  15 . If not, go to step  12 .
  10. Disconnect the jumper wires. Test the cooling fan speed signal circuit of the cooling fan clutch for an open. Did you find and correct the condition? If so, go to step  15 . If not, go to step  12 .
  11. Inspect for a poor connection at the harness connector of the cooling fan clutch. Did you find and correct the condition? If so, go to step  15 . If not, go to step  13 .
  12. Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If so, go to step  15 . If not, go to step  14 .
  13. Replace the cooling fan clutch. See FAN CLUTCH  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  15 .
  14. Replace and program the PCM. See appropriate REMOVAL & INSTALLATION article in ENGINE PERFORMANCE. Did you complete the replacement? If so, go to next step.
  15. Use the scan tool in order to clear the DTCs. Operate the vehicle within the CONDITIONS FOR RUNNING THE DTC  . Does the DTC reset? If so, go to step  2 . If not, system is OK.
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