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Home >> Buick >> 2001 >> Century Limited >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls Self-Diagnostics - 3.1L & 3.4L >> Diagnostic Tests >> DTC P0481: Cooling Fan Relay No. 2 Control Circuit >> Diagnostic Procedure (Century, Impala & Monte Carlo)

Diagnostic Procedure (Century, Impala & Monte Carlo)

  1. Perform engine cooling diagnostic system check. See ENGINE COOLING DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing engine cooling diagnostic system check, go to next step.
  2. Turn ignition on. Using scan tool, command high speed cooling fans on and off. Listen for cooling fan relay operation. Cooling fan relays are located in underhood fuse block. Cooling fan relays No. 2 and 3 should operate. If relays turn on and off with each command, see DIAGNOSTIC AIDS . If operation is not as specified, go to next step.
  3. Turn ignition off. Remove cooling relay No. 3. Turn ignition on. Connect a test light between ground and coil feed circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step  10.
  4. Connect test light between control circuit and battery feed circuit of cooling fan relay No. 3. Using scan tool, command high speed cooling fans on and off. If test light turns on and off with each command, go to step  9. If test light does not respond as specified, go to next step.
  5. If test light remains illuminated with each command, go to step  7. If test light does not remain illuminated with each command, go to next step.
  6. Check for open or short to voltage in high speed cooling fan relay control circuit between cooling fan relays No. 2 and 3, and PCM harness connector C1 terminal No. 5 (Dark Blue wire). See Figure. See PCM LOCATION . Repair circuit as necessary, then go to step  12. If circuit is okay, go to step  9.
  7. Check for short to ground in high speed cooling fan relay control circuit between cooling fan relays No. 2 and 3, and PCM harness connector C1 terminal No. 5 (Dark Blue wire). See Figure. See PCM LOCATION . Repair circuit as necessary, then go to step  12. If circuit is okay, go to step  9.
  8. Check for open or short to ground in coil feed circuit for cooling fan relays No. 2 and 3. Repair circuit as necessary, then go to step  12. If circuit is okay, go to step  10.
  9. Inspect PCM harness connector for poor connections. Repair connector as necessary, then go to step  12. If connector is okay, go to step  11.
  10. Repair short to ground in cooling fan motor supply voltage circuit. See WIRING DIAGRAMS article. After repairs, go to step  12.
  11. Replace PCM. Program replacement PCM using required equipment. See PROGRAMMING . After repairs, go to next step.
  12. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, system is okay. If scan tool does not indicate that this test ran and passed, go to step  2.
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