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Home >> Oldsmobile >> 1997 >> Silhouette Base, Van Passenger Extended >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - System/Component Tests >> Miscellaneous Pcm/VCM Controls >> Electric Cooling Fan Circuit Diagnosis >> Cooling Fan Circuit Diagnosis

Cooling Fan Circuit Diagnosis

  1. If Powertrain On-Board Diagnostic (OBD) System Check has not been performed, see the BASIC TESTING article and go to OBD SYSTEM CHECK. If OBD SYSTEM CHECK has been performed, go to next step.
  2. Check for PCM Diagnostic Trouble Codes (DTCs). If any DTCs are present, perform testing for applicable DTC. Repair all DTCs that are set before proceeding with testing. See the TESTS W/CODES article. If no DTCs are present, go to next step.
  3. Ensure engine coolant temperature is less than 212°F (100°C). Turn A/C off. Turn ignition on. If cooling fans go off, go to next step. If cooling fans do not go off, go to step 32).
  4. Using scan tool, select RELAY CONTROL function. Command low speed fans on. If cooling fans operate at low speed, go to next step. If cooling fans do not operate as specified, go to step 8).
  5. Command high speed fans on. Wait 6 seconds. If cooling fans operate at high speed, go to next step. If cooling fans do not operate as specified, go to step 58).
    NOTE: Ensure ambient temperature is greater than 48°F (9°C) before proceeding.
  6. Exit scan tool OUTPUT TESTS. Start engine. Turn A/C on. If cooling fans come on, go to DIAGNOSTIC AIDS. If cooling fans do not come on, go to next step.
  7. Using scan tool, view A/C REQUEST on display. If YES is displayed, go to step 77). If YES is not displayed, go to A/C CLUTCH CIRCUIT DIAGNOSIS TEST in A/C COMPRESSOR CLUTCH CONTROLS  .
  8. If either cooling fan is running, go to next step. If neither cooling fan runs, go to step 16).
  9. If cooling fan No. 1 runs, go to next step. If cooling fan No. 1 does not run, go to step 14).
  10. Turn ignition off. Disconnect cooling fan No. 2 harness connector. Turn ignition on. Using scan tool, select RELAY CONTROL function. Command low speed fans on. If cooling fan No. 1 runs, go to next step. If cooling fan No. 1 does not run, go to step 80).
  11. Remove cooling fan relay (5-pin) from underhood electrical center. If cooling fan No. 1 runs, go to next step. If cooling fan No. 1 does not run, go to step 13).
  12. Locate and repair short to ground in circuit No. 532 (Gray wire). Go to step 81).
  13. Check circuit No. 409 (Light Blue wire), and/or circuit No. 473 (Dark Blue wire) for a short to ground. Repair as necessary. After repairs, go to step 81). If no problem was found, go to step 70).
  14. Turn ignition off. Disconnect cooling fan No. 1 harness connector. Turn ignition on. Using scan tool, select RELAY CONTROL function. Command low speed fans on. If cooling fan No. 2 runs, go to next step. If cooling fan No. 2 does not run, go to step 71).
  15. Replace cooling fan No. 1 diode. Go to step 81).
  16. Turn ignition on. Remove No. 1 cooling fan relay from underhood electrical center. Using a test light connected to ground, probe No. 1 cooling fan relay cavity No. 87. If test light comes on, go to step 18). If test light does not come on, go to next step.
  17. Check for blown Maxi-fuse that supplies power to No. 1 cooling fan relay. If fuse is blown, locate and repair short circuit. Possible causes for short circuit are:
    • Seized cooling fan motors.
    • Shorted cooling fan motor windings.
    • Short to ground in circuit No. 504.
    • Short to ground in power feed circuit between fuse and No. 1 cooling fan relay.

    If fuse is not blown, check for an open in power feed circuit between fuse and No. 1 cooling fan relay. Repair as necessary. Go to step 81).

  18. Using a test light connected to ground, probe No. 1 cooling fan relay cavity No. 86. If test light comes on, go to step 20). If test light does not come on, go to next step.
  19. Check for blown Maxi-fuse that supplies power to No. 1 cooling fan relay. If fuse is blown, locate and repair short circuit. Possible causes for short circuit are:
    • Seized cooling fan motors.
    • Shorted cooling fan motor windings.
    • Short to ground in circuit No. 504.
    • Shorted relay coil in cooling fan relay.
    • Short to ground in power feed circuit between fuse and No. 1 cooling fan relay.

    If fuse is not blown, check for an open in power feed circuit between fuse and No. 1 cooling fan relay. Repair as necessary. Go to step 81).

  20. Turn ignition off. Disconnect both cooling fan harness connectors. Using fused jumper wires, jumper terminals "A" and "B" together at both harness connectors. Turn ignition on. Connect a test light between No. 1 cooling fan relay cavities No. 30 and 87. If test light comes on, go to next step. If test light does not come on, go to step 27).
  21. Connect a test light between No. 1 cooling fan relay cavities No. 85 and 86. Turn ignition on. Using scan tool, select RELAY CONTROL function. Command low speed fans on. If test light comes on, go to next step. If test light does not come on, go to step 25).
  22. Turn ignition off. Remove jumper wires and reconnect cooling fan harness connectors. Connect a fused jumper wire between No. 1 cooling fan relay cavities No. 30 and 87. Turn ignition on. If both cooling fans run, go to next step. If both cooling fans do not run, go to step 24).
  23. Check for poor connections at No. 1 cooling fan relay in underhood electrical center. Repair as necessary. Go to step 81). If no problem was found, go to step 37).
  24. Check for poor connections at both cooling fan motors. Repair as necessary. Go to step 81). If no problem was found, go to step 63).
  25. Turn ignition off. Disconnect PCM harness connector C1. Install a fused jumper wire between No. 1 cooling fan relay cavities No. 85 and 86. Turn ignition on. Using a test light connected to ground, probe PCM harness connector C1, terminal No. 32 (Dark Green wire). If test light comes on, go to step 77). If test light does not come on, go to next step.
  26. Locate and repair open in circuit No. 335 (Dark Green wire) between No. 1 cooling fan relay and PCM harness connector C1, terminal No. 32. Go to step 81).
  27. Turn ignition off. Remove jumper wires and reconnect cooling fan harness connectors. Connect a fused jumper wire between No. 1 cooling fan relay cavities No. 30 and 87. Remove cooling fan relay (5-pin) from underhood electrical center. Using a test light connected to ground, probe cooling fan relay (5-pin) cavity No. 30. If test light comes on, go to next step. If test light does not come on, go to step 31).
  28. Connect a test light between cooling fan relay (5-pin) cavities No. 30 and 87A. If test light comes on, go to step 30). If test light does not come on, go to next step.
  29. Check for open in circuit No. 409 (Light Blue wire) between cooling fan relay (5-pin) cavity No. 87A and harness connector terminal "B" at cooling fan motor No. 2. Repair as necessary. Go to step 81). If no problem was found, go to step 57).
  30. Check for poor connections at cooling fan relay (5-pin) cavities No. 30 and 87A in underhood electrical center. Repair as necessary. Go to step 81). If no problem was found, go to step 76).
  31. Check for an open in circuit No. 504 (White wire) between No. 1 cooling fan relay cavity No. 30 and harness connector terminal "B" at cooling fan motor No. 1. Repair as necessary. Go to step 81). If no problem was found, go to step 56).
  32. Using scan tool, view A/C REQUEST on display. If YES is displayed, go to appropriate A/C CLUTCH CIRCUIT DIAGNOSIS TEST in A/C COMPRESSOR CLUTCH CONTROLS  . If YES is not displayed, go to next step.
  33. If both cooling fans are operating at low speed, go to next step. If both cooling fans do not operate at low speed, go to step 40).
  34. Remove No. 1 cooling fan relay from underhood electrical center. If both cooling fans run, go to next step. If both cooling fans do not run, go to step 36).
  35. Locate and repair short to power in circuit No. 504 (White wire). Go to step 81).
  36. Using a test light connected to battery positive, probe No. 1 cooling fan relay cavity No. 85. If test light comes on, go to step 38). If test light does not come on, go to next step.
  37. Replace No. 1 cooling fan relay. Go to step 81).
  38. Turn ignition off. Disconnect PCM harness connector C1. Using a test light connected to battery positive, probe No. 1 cooling fan relay cavity No. 85. If test light come on, go to next step. If test light does not come on, go to step 77).
  39. Locate and repair short to ground in circuit No. 335 (Dark Green wire) between No. 1 cooling fan relay and PCM harness connector C1, terminal No. 32. Go to step 81).
  40. If both cooling fans operate at high speed, go to next step. If both cooling fans do not operate at high speed, go to step 42).
  41. Using scan tool, view A/C PRESSURE on display. If reading is less than 1.2 volts, go to step 77). If reading is 1.2 volts or greater, go to step 44).
  42. Turn ignition off. Disconnect PCM harness connector C1. Turn ignition on. If cooling fan No. 2 operates at high speed, go to next step. If cooling fan No. 2 does not operate at high speed, go to step 77).
  43. Check for a short to ground in circuit No. 473 to cooling fan relay (5-pin) and relay No. 2 control circuit (Dark Blue wire). Repair as necessary. Go to step 81). If no problem was found, go to step 52).
  44. Turn ignition off. Disconnect A/C pressure sensor harness connector. Turn ignition on. Using scan tool, view A/C PRESSURE on display. If reading is near zero volts, go to step 46). If reading is not as specified, go to next step.
  45. Using a voltmeter, measure voltage between A/C pressure sensor signal and ground circuits. If reading is near zero volts, go to step 77). If reading is not as specified, go to step 51).
  46. Using a test light connected to battery positive, probe A/C pressure sensor ground circuit. If test light comes on, go to next step. If test light does not come on, go to step 49).
  47. Using a voltmeter, measure voltage between A/C pressure sensor 5-volt reference and sensor ground. If reading is near 5 volts, go to next step. If reading is not as specified, go to step 50).
  48. Replace A/C pressure sensor. Go to step 81).
  49. Locate and repair open or short to power in A/C pressure sensor ground circuit. Go to step 81).
  50. Locate and repair open or short to ground in A/C pressure sensor 5-volt reference circuit. Go to step 81).
  51. Locate and repair short to power in A/C pressure sensor signal circuit. Go to step 81).
  52. Remove No. 2 cooling fan relay from underhood electrical center. If cooling fan No. 2 operates at high speed, go to next step. If cooling fan No. 2 does not operate at high speed, go to step 70).
  53. Remove cooling fan relay (5-pin) from underhood electrical center. If cooling fan No. 2 operates at high speed, go to next step. If cooling fan No. 2 does not operate at high speed, go to step 55).
  54. Locate and repair short to power in circuit No. 409 (Light Blue wire) between No. 2 cooling fan relay and cooling fan motor No. 2. Go to step 81).
  55. Locate and repair short to power in circuit No. 532 (Dark Blue wire) between cooling fan relay (5-pin) and cooling fan motor No. 1. Go to step 81).
  56. Check for an open in circuit No. 532 (Dark Blue wire) between cooling fan relay (5-pin) cavity No. 30 and terminal "A" of cooling fan motor No. 1 harness connector. Repair as necessary. Go to step 81). If no problem was found, go to step 79).
  57. Check for an open in circuit No. 1050 (Black wire) between cooling fan motor No. 2 harness connector terminal "A" and ground. Repair as necessary. Go to step 81). If no problem was found, go to step 80).
  58. Turn ignition on. Remove No. 2 cooling fan relay from underhood electrical center. Connect a test light between No. 2 cooling fan relay cavity No. 86 and battery positive. Using scan tool, select RELAY CONTROL function. Command high speed fans on. Wait 6 seconds. If test light comes on, go to step 61). If test light does not come on, go to next step.
  59. Remove cooling fan relay (5-pin) from underhood electrical center. Connect a test light between cooling fan relay (5-pin) cavity No. 86 and battery positive. Using scan tool, select RELAY CONTROL function. Command high speed fans on. Wait 6 seconds. If test light comes on, go to step 78). If test light does not come on, go to next step.
  60. Turn ignition off. Disconnect PCM harness connector C1. Check circuit No. 473 (Dark Blue wire) for an open or short to power. Repair as necessary. Go to step 81). If no problem is found, go to step 77).
  61. Turn ignition off. Reinstall No. 2 cooling fan relay. Disconnect both cooling fan motor harness connectors. Turn ignition on. Using scan tool, select RELAY CONTROL function. Command high speed fans on. Wait 6 seconds. Using a test light connected to ground, probe terminal "B" of cooling fan motor No. 2 harness connector. If test light comes on, go to next step. If test light does not come on, go to step 64).
  62. Using a test light connected to battery positive, probe terminal "A" of cooling fan motor No. 1 harness connector. If test light comes on, go to next step. If test light does not come on, go to step 71).
  63. Check for a seized cooling fan motor or open motor winding. Replace appropriate cooling fan motor. Go to step 81).
  64. Turn ignition off. Remove No. 2 cooling fan relay from underhood electrical center. Turn ignition on. Using a test light connected to ground, probe No. 2 cooling fan relay cavity No. 85. If test light comes on, go to step 66). If test light does not come on, go to next step.
  65. Locate and repair open in battery positive circuit to No. 2 cooling fan relay. Check for blown Maxi-fuse (30-amp). Repair short to ground if blown. Replace fuse. Go to step 81).
  66. Using a test light connected to ground, probe No. 2 cooling fan relay cavity No. 30. If test light comes on, go to step 68). If test light does not come on, go to next step.
  67. Locate and repair open in battery positive circuit to No. 2 cooling fan relay cavity No. 30. Go to step 81).
  68. Check for open in circuit No. 409 (Light Blue wire) between cooling fan motor No. 2 harness connector terminal "B" and No. 2 cooling fan relay cavity No. 87. Repair as necessary. Go to step 81). If no problem was found, go to next step.
  69. Check for poor connections at No. 2 cooling fan relay in underhood electrical center. Repair as necessary. Go to step 81). If no problem was found, go to next step.
  70. Replace No. 2 cooling fan relay. Go to step 81).
  71. Turn ignition off. Remove cooling fan relay (5-pin) from underhood electrical center. Turn ignition on. Using a test light connected to ground, probe cooling fan relay (5-pin) cavity No. 85. If test light comes on, go to step 73). If test light does not come on, go to next step.
  72. Locate and repair open in battery positive circuit to cooling fan relay (5-pin) cavity No. 85. Go to step 81).
  73. Using a test light connected to battery positive, probe cooling fan relay (5-pin) cavity No. 87. If test light comes on, go to step 75). If test light does not come on, go to next step.
  74. Locate and repair open in circuit No. 1050 (Black wire) between cooling fan relay (5-pin) cavity No. 87 and ground. Go to step 81).
  75. Check for poor connections at cooling fan relay (5-pin) in underhood electrical center. Repair as necessary. Go to step 81). If no problem was found, go to step 76).
  76. Replace cooling fan relay (5-pin). Go to step 81).
  77. Replace PCM. Go to step 81).
  78. Repair open in circuit No. 473 (Dark Blue wire) between PCM harness connector C1, terminal No. 31 and cooling fan relays (5-pin and No. 2) cavity No. 86. Go to step 81).
  79. Replace cooling fan motor No. 1. Go to step 81).
  80. Replace cooling fan motor No. 2. Go to step 81).
  81. Ensure coolant temperature is less than 212°F (100°C). Turn A/C off. Start engine and let idle. If cooling fans are running, go to step 32). If cooling fans are not running, go to next step.
  82. Using scan tool, select RELAY CONTROL function. Command low speed fans on. If both cooling fans operate at low speed, go to next step. If both cooling fans do not operate at low speed, go to step 8).
  83. Command high speed cooling fans on. Wait 6 seconds. If both cooling fans operate at high speed, system is okay at this time. If both cooling fans do not operate at high speed, go to step 58).
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