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DTC P0495: 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. With a scan tool, observe the Powertrain DTC list. Start the engine. Operate the vehicle within the Conditions for Running in the DTC. Does the scan tool indicate the DTC Failed this ignition cycle? If so, go to step  5 . If not, go to next step.
    3. NOTE: DTC P1482 (4.2L engine) will set when the cooling fan relay is disconnected.
  3. Turn OFF the ignition. Disconnect the coolant fan relay. 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. Start the engine. Raise engine speed to 2000 RPM for 2 minutes. Does the cooling fan engage? If so, go to next step. If not, go to step  5 .
    4. NOTE: Continuously excessive fan noise is due to the PCM commanding the cooling fan 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 will not correct the condition.
  4. Turn OFF the ignition. Remove the 10-amp fused jumper wire. Install cooling fan relay. Disconnect the cooling fan connector. Start the engine. Raise engine speed to 2000 RPM for 2 minutes. Does the cooling fan disengage? If so, go to next step. If not, go to step  11 .
  5. Install a scan tool. Start the engine. With a scan tool, observe the Fan Speed parameter in the PCM ENG 2 data list. Operate the engine at 2000 RPM for 2 minutes. Is the cooling fan speed less than 1600 RPM? If so, go to DIAGNOSTIC AIDS  . If not, go to next step.
  6. Turn OFF the ignition. Disconnect the cooling fan connector. Start the engine. Run the engine at 2000 RPM for 2 minutes. Turn OFF the engine. Rotate the cooling fan 2 revolutions. Does the cooling fan rotate freely? If so, go to next step. If not, go to step  13 .
  7. Disconnect the harness connector at the shroud. Turn ON the ignition. Connect a test lamp between the cooling fan clutch supply voltage circuit of the cooling fan and ground. Does the test lamp illuminate? If so, go to next step. If not, go to step  11
  8. Disconnect the cooling fan relay. Does the test lamp remain illuminated? If so, go to next step. If not, go to step  10 .
  9. Repair the cooling fan clutch supply voltage circuit of the cooling fan for a short to voltage. Did you complete the repair? If so, go to step  14 .
  10. Inspect for poor connections at the cooling fan relay. See INTERMITTENT OR POOR CONNECTIONS  under TROUBLE SHOOTING. Did you find and correct the condition? If so, go to step  14 . If not, go to step  12 .
  11. Inspect for poor connections at the cooling fan. See INTERMITTENT OR POOR CONNECTIONS  under TROUBLE SHOOTING. Did you find and correct the condition? If so, go to step  14 . If not, go to next step.
  12. Replace the cooling fan relay. See COOLING FAN RELAY  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  14 .
  13. Replace the cooling fan. See FAN CLUTCH  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
  14. 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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