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Home >> Oldsmobile >> 1996 >> Aurora >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1660 - Cooling Fan Control Circuits >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Turn ignition on. Turn off A/C. Using scan tool in MISC TESTS, select OUTPUT TESTS then select FAN RELAYS. Command all relays off and note QUAD DRIVER 1. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 9).
  3. Command all relays off and note QUAD DRIVER 1 display on scan tool. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 6).
  4. Turn ignition on, with engine off. Command STARTER INHIBIT on. If QUAD DRIVER 1 on scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 20).
  5. If cooling operation fault is suspected, diagnose cooling fan. See SYSTEM/COMPONENT TESTS article. If cooling fan is operating properly, fault it not present.
  6. While noting QUAD DRIVER 1 display, command FAN RELAY 1 on. If scan tool display indicates OK, go to step 8). If scan tool display does not indicate OK, go to next step.
  7. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Remove cooling fan relay No. 1 (low speed). Turn ignition on. Using DVOM, check voltage between ground and cooling fan low speed control circuit at PCM harness connector C2 terminal. If voltage reading is .5 volt or less, go to step 27). If voltage reading is greater than .5 volt, go to step 18).
  8. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Remove cooling fan relays No. 2 and 3. Turn ignition on. Using DVOM, check voltage between ground and cooling fan high speed control circuit at PCM harness connector C2. If voltage reading is .5 volt or less, go to step 27). If voltage reading is greater than .5 volt, go to step 19).
  9. In ENGINE 3 data list mode, note PASSKEY STARTER display on scan tool. If scan tool display indicates ENABLED, go to next step. If scan tool display does not indicate ENABLED, go to step 21).
  10. With all relays still commanded off, observe operation of both cooling fans. If either fan operates, go to next step. If either fan does not operate, go to step 12).
  11. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and cooling fan low speed control circuit at PCM harness connector C2. If voltage reading is 10 volts or greater, go to step 16). If voltage reading is less than 10 volts, go to step 17).
  12. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and cooling fan high and low speed control circuits at PCM harness connector C2. If voltage reading on both terminals is 10 volts or greater, go to step 27). If voltage reading on both terminals is less than 10 volts, go to next step.
  13. If voltage measured is low on both terminals, go to step 15). If voltage measured is low only on one of the terminals, go to next step.
  14. Repair open circuit or replace open cooling fan relay for circuit that measured low in step 9).
  15. Repair cause of no voltage to both circuits. Replace fuse, if faulty. A no voltage to both circuits can be caused by, open in both the high and low cooling fan control circuits, open in ignition circuit to both relays, short to ground in ignition circuit to both relays (fuse blown), short fan relay(s), short to ground in ignition circuit to A/C compressor relay (fuse blown) or shorted A/C compressor relay (blown fuse).
  16. Repair short to ground in cooling fan high speed control circuit.
  17. Repair short to ground in cooling fan low speed control circuit.
  18. Repair short to voltage in cooling fan low speed control circuit.
  19. Repair short to voltage in cooling fan high speed control circuit.
  20. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2 and PASS-Key(R) module harness connector. Turn ignition on. Using DVOM, check voltage between ground and starter inhibit output circuit at PCM harness connector C2. If voltage reading is greater than .5 volt, go to step 24). If voltage reading is less than .5 volt, go to step 27).
  21. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and starter inhibit output circuit at PCM harness connector C2. If voltage reading is 10 volts or greater, go to step 27). If voltage reading less than 10 volts, go to next step.
  22. Turn ignition off. Disconnect PASS-Key(R) module harness connector. Check resistance between ground and starter inhibit output circuit at PCM harness connector C2. If resistance is 10,000 ohms or greater, go to next step. If resistance is greater than 10,000 ohms, go to step 25).
  23. Check resistance on starter inhibit output circuit between PCM harness connector C2 and PASS-Key(R) harness connector terminals. If resistance is less than 5 ohms, fault is not present. Diagnose anti-theft deterrent system. See appropriate ANTI-THEFT SYSTEM article in the ACCESSORIES/SAFETY EQUIPMENT section. If resistance is greater than 5 ohms, go to step 26).
  24. Repair short to voltage in starter inhibit output circuit.
  25. Repair short to ground in starter inhibit output circuit.
  26. Repair open in starter inhibit output circuit.
  27. Check terminal contact at PCM. Repair as necessary. If terminal contact is okay, go to next step.
  28. Replace PCM. Program replacement PCM using required equipment.
Fig 1: DTC P1660 Schematic
G96I01715
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