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Home >> Chevrolet >> 2000 >> Venture Plus >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0481: Cooling Fan Relay No. 2 Control Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
    2. NOTE: To determine if relay responds correctly to scan tool command, observe cooling fans. With relay No. 2 commanded on, both cooling fans should run at low speed, then after several seconds both cooling fans should switch to high speed.
  2. Turn ignition on, with engine off. Using scan tool, command cooling fan relays No. 2 and 3 on and off. If both relays turn on after several seconds, and then turn off with each command, see DIAGNOSTIC AIDS . If operation is not as specified, go to next step.
  3. Turn ignition off. Disconnect relays No. 2 and 3. Turn ignition on, with engine off. Using a test light connected to ground, probe coil feed circuits for each relay. If test light illuminates for both circuits, go to next step. If test light does not illuminate for both circuits, go to step  10.
  4. Connect test light between control circuits of each relay and battery feed circuits of each relay. Using scan tool, command relays No. 2 and 3 on and off. If test light turns on after several seconds, and then turns off with each command on both relays, go to step  8. If test light does not respond as specified, go to next step.
  5. If test light remains illuminated with each command when probing either battery feed circuit, go to step  7. If test light does not remain illuminated with each command when probing either battery feed circuit, go to next step.
  6. Check control circuit of each relay for an open or short to voltage. Repair as necessary. After repairs, go to step  13. If circuits are okay, go to step  9.
  7. Check control circuit of each relay for a short to ground. Repair as necessary. After repairs, go to step  13. If circuits are okay, go to step  9.
  8. Check for faulty relay connections. Repair as necessary. After repairs, go to step  13. If connections are okay, go to step  11.
  9. Check for faulty PCM harness connections. Repair as necessary. After repairs, go to step  13. If connections are okay, go to step  12.
  10. Repair battery feed circuit to affected relay. After repairs, go to step  13.
  11. Replace affected relay. After replacing relay, go to step  13.
  12. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  13. 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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