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Engine System Testing & Engine Component Testing - 3.1L: Diagnosis Oldsmobile Cutlass VI

Testing & Diagnostics ~5331 words

A/C ON (A/C REQUEST) SWITCH TEST

  1. Start engine and allow to idle. If a scan tool is available, scan A/C request parameter. Slide mode selector for A/C back and forth between ON and OFF positions. Scan status should change.
  2. If scan tool is not available or scan status does not change, measure voltage between ground and PCM A/C request terminal. For wiring schematics, see appropriate diagram in the WIRING DIAGRAMS article.
  3. With A/C mode selector in the ON position, battery voltage should be present. If battery voltage is not present, check for open between A/C mode select switch and PCM A/C request terminal, low A/C refrigerant level causing low pressure switch to open, bad A/C fuse or bad A/C mode select switch.

Fuel Injector Balance Test

The injector balance test is used to pulse the injector for a precise amount of time, spraying a measured amount of fuel in the intake manifold. As each injector is pulsed, a drop in fuel rail pressure occurs. This pressure drop can be recorded and compared to other injectors. An injector with a pressure drop of 1.5 psi (.11 kg/cm 2 ) or more, greater than or less than other injectors, should be considered faulty.

Note. Allow engine to cool down to avoid irregular readings due to "hot soak" fuel boiling. To prevent flooding, the FUEL INJECTOR BALANCE TEST should not be performed more than once without starting and running engine.

CAUTIONTo avoid possible vehicle fire, wrap a shop towel around fitting to absorb fuel spillage.
  1. Ensure engine is at normal operating temperature. Connect Fuel Pressure Gauge (J-34730-1) to pressure test port. Energize fuel pump using fuel pump test connector or Tech 1 scan tool.
  2. Bleed air from fuel gauge and hose to ensure accurate gauge reading. Repeat this procedure until all air is bled from system. Run fuel pump and note fuel pressure. Fuel pressure should be as specified. See «FUEL PRESSURE RANGE CHART»(ref-20534-S37590437662001010200000) . If fuel pressure range is not as specified, see BASIC FUEL SYSTEM CHECKS in the «BASIC TESTING - 3.1L»(ref-20651) article.
  3. Turn fuel pump off. When fuel pump stops, pressure may slightly drop then should hold steady. If fuel pressure does not hold steady, refer to BASIC FUEL SYSTEM CHECKS in the «BASIC TESTING - 3.1L»(ref-20651) article.
  4. Install Fuel Injector Tester (J-39021) to an injector. Set amperage supply selector switch to BALANCE TEST, 0.5-2.5 AMP position. Cycle fuel pump on and off to pressurize fuel system. Record stabilized fuel pressure.
  5. Depress PUSH TO START TEST button on fuel injector tester to energize injector. Note fuel pressure the instant fuel gauge needle stops. Record fuel pressure reading. Perform the same test to all injectors.
  6. To obtain pressure drop values, subtract second pressure reading from first pressure reading on each injector. Add all pressure drop values and divide by number of injectors to obtain an average pressure drop.
  7. Retest an injector that appears faulty. Replace any injector with a 1.5 psi (.11 kg/cm 2 ) difference, either greater than or less than the average pressure drop. If injectors are all okay, remove test equipment, plug in disconnected harness connectors and review SYMPTOMS in the «TESTS W/O CODES - 3.1L»(ref-20702) article.
ApplicationPsi (kg/cm 2 )
3.1L41-47 (2.9-3.3)

FUEL PRESSURE RANGE CHART

Injector Leak Test

  1. Turn engine off. Relieve fuel pressure. Access fuel injector harness connector. Connect Fuel Injector Tester (J-39021) to vehicle battery and to a fuel injector. If coolant temperature is 50-95°F (10-35°C), go to next step. If coolant temperature is not 50-95°F (10-35°C), go to step 5).
  2. Set fuel injector tester's amperage supply selector switch to COIL TEST 0.5 AMP position. Connect a Digital Volt-Ohmmeter (DVOM) to fuel injector tester. Set DVOM to tenths scale (0.0).
  3. Ensure engine coolant temperature is 50-95°F (10-35°C). Press PUSH TO START TEST button. Observe DVOM. Voltage reading may climb during test. Record lowest voltage displayed immediately after activation.
  4. Perform voltage reading on all injectors. If voltage reading is erratic or falls out of specified range, perform injector balance test or replace faulty injector. See INJECTOR TEST VOLTAGE RANGE table or FUEL INJECTOR BALANCE TEST.
  5. Press PUSH TO START button on fuel injector tester. Observe DVOM. Voltage reading may climb during test. Record lowest voltage displayed immediately after activation. Perform voltage reading at least twice on all injectors.
  6. If voltage reading is erratic or is greater than 9.5 volts, replace affected fuel injector. If voltage reading is not erratic or not greater than 9.5 volts, go to next step.
  7. From recorded voltages (except readings greater than 9.5 volts), identify highest voltage reading and subtract from the other recorded voltages. If subtracted value is greater than 0.6 volts, replace affected fuel injector. If subtracted value is less than 0.6 volts, perform injector balance test. See FUEL INJECTOR BALANCE TEST.
ApplicationVolts
3.1L5.7-6.6

INJECTOR TEST VOLTAGE RANGE

System Test (Vacuum Operated)

Start and run engine to normal operating temperature. With engine at idle, push up on underside of EGR diaphragm. RPM should drop as EGR valve is opened. If RPM does not drop, remove EGR valve and check for blocked EGR passages. If RPM drops as diaphragm is lifted and EGR vacuum supply is regulated by an PCM-controlled solenoid, verify vacuum is available to solenoid at 2000 RPM and check solenoid using appropriate procedure. See appropriate EGR CONTROL SOLENOID procedure.

CAUTIONWear gloves if handling EGR valve when it is hot.

Warning Light Diagnosis

  1. Perform On-Board Diagnostics (OBD) System check. See the «BASIC TESTING - 3.1L»(ref-20651) article. After performing OBD system check, go to next step.
  2. Check instrument cluster. See the INSTRUMENT PANEL article in the ACCESSORIES/SAFETY EQUIPMENT section. If instrument panel is okay, go to next step.
  3. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using a DVOM, check voltage between affected PCM output circuit at PCM harness connector terminal and ground. See appropriate diagram in the WIRING DIAGRAMS article. Battery voltage should be present. If battery voltage is present, go to next step. If battery voltage was not present, go to step 7).
  4. Set DVOM to 10-amp scale. Check current between affected PCM output circuit and ground. Monitor reading for about 2 minutes. DVOM should read .05-1.50 amps. If reading is as specified, go to step 12). If reading is not as specified, go to next step.
  5. Disconnect instrument panel cluster, but leave PCM connector disconnected. Using DVOM, check voltage between affected PCM output circuit and ground. DVOM should read zero volts. If voltage reading is as specified, go to step 15). If voltage reading is not as specified, go to next step.
  6. Locate and repair short to voltage in affected PCM output circuit. After repairs, go to step 17).
  7. Check ignition feed fuse for instrument panel cluster indicator lights. If fuse is blown, go to next step. If fuse is okay, go to step 9)
  8. Locate and repair short to ground in ignition feed circuit for instrument panel cluster indicator lights. Replace fuse and go to step 17).
  9. Disconnect instrument cluster connector. Turn ignition on. Check voltage between ignition feed circuit for instrument panel cluster indicator lights and ground. Battery voltage should be present. If battery voltage is present, go to next step. If battery voltage was not present, go to step 14).
  10. Check affected PCM output circuit for an open or shorted circuit to ground. If circuit is open or shorted, go to step 17). If circuit was okay, go to next step.
  11. Check affected PCM output circuit and ignition feed circuit for poor connection at instrument panel cluster and at PCM. If problem is present, repair as necessary and then go to step 17). If problem was not present, go to step 15).
  12. Turn ignition off. Reconnect PCM harness connector. Disconnect instrument cluster connector. Turn ignition on. Connect a test light between affected PCM output circuit and ignition feed circuit at instrument panel harness connector. Using a scan tool, perform OUTPUT TESTS function to cycle affected warning light on and off. If test light flashes on and off, check for shorted component or circuit in the output driver circuit. Check for faulty instrument cluster. If test light does flash on and off, go to next step.
  13. Check affected PCM output circuit for poor connection to PCM. Replace defective terminal and then go to step 17). If terminal is okay, go to step 16).
  14. Repair open in ignition feed circuit to instrument panel cluster indicator lights. After repairs, go to step 17).
  15. Replace instrument cluster and then go to step 17).
  16. Replace PCM and then go to next step.
  17. Using scan tool, operate affected warning light. If warning light does not operate properly, go to step 3).

Compressor Clutch Control Circuit Diagnosis

  1. If On-Board Diagnostic (OBD) System Check has not been performed, see the «BASIC TESTING - 3.1L»(ref-20651) article and go to OBD SYSTEM CHECK. If OBD SYSTEM CHECK has been performed, go to next step.
  2. Install scan tool. Check if any Diagnostic Trouble Codes (DTCs) are stored. If any DTCs are set, perform diagnosis for DTCs first. See the «TESTS W/CODES - 3.1L»(ref-20533) article. If no DTCs are set, go to next step.
  3. Ensure ambient air temperature is greater than 41°F (5°C), A/C pressure is greater than 35 psi (.40 volt on scan tool), and coolant temperature is less than 250°F (121°C). Turn A/C off. Turn ignition on, engine off. Listen for engagement of A/C compressor clutch. If A/C compressor clutch engages, go to step 19). If A/C compressor clutch does not engage, go to next step.
  4. With engine running at idle, select DEFROST or MAX mode. Observe A/C compressor clutch. If A/C compressor clutch is engaged, problem may be intermittent. If A/C compressor clutch is not engaged, go to next step.
  5. With DEFROST or MAX mode selected, monitor A/C REQUEST display on scan tool engine data list. If A/C REQUEST displays YES, go to step 9). If A/C REQUEST does not display YES, go to next step.
  6. Turn ignition off. Disconnect PCM harness connector C1. Turn ignition on. With DEFROST or MAX mode selected, use a voltmeter and measure voltage on A/C request circuit at PCM harness connector C1, terminal No. 62. If battery voltage is present, go to step 8). If battery voltage is not present, go to next step.
  7. Check A/C request circuit for an open, short to ground, or poor connection at A/C control head/programmer. Repair as necessary. Go to step 30). If no problem is found, diagnose A/C controls.
  8. Check A/C request circuit for a poor connection at PCM. Repair as necessary. Go to step 30). If no problem is found, go to step 28).
  9. Observe A/C refrigerant pressure display on scan tool. If pressure is 36-440 psi (2.5-30.9 kg/cm 2 ), go to step 12). If pressure is not as specified, go to next step.
  10. Install A/C manifold gauge set. Observe high-side refrigerant pressure. If pressure is 36-440 psi (2.5-30 kg/cm 2 ), go to next step. If pressure is not as specified, charge A/C system using approved A/C refrigerant recovery/recycling equipment. Go to step 30).
  11. Turn ignition off. Disconnect A/C pressure sensor. Turn ignition on. View A/C HIGH-SIDE display on scan tool engine data list. If scan tool displays A/C high-side pressure as 0 psi (0 kg/cm 2 ), go to step 29). If scan tool does not display A/C high-side pressure as specified, go to step 28).
  12. Disconnect A/C relay. Using a test light connected to ground, probe circuit No. 1239 (ignition feed) at A/C relay harness connector. If test light comes on, go to next step. If test light does not come on, go to step 24).
  13. Using a test light connected to battery positive, probe Dark Green/White wire at A/C relay harness connector. If test light comes on, go to next step. If test light does not come on, repair open in Dark Green/White wire. Go to step 30).
  14. Connect a fused jumper between circuit No. 1239 (ignition feed) and A/C compressor clutch ignition feed circuit (Dark Green wire) at A/C relay connector. If A/C compressor clutch engages, go to next step. If A/C compressor clutch does not engage, leave jumper wire in place and go to step 16).
  15. Check for poor connections at A/C relay. Repair as necessary. Go to step 30). If no problem is found, go to step 25).
  16. Disconnect A/C compressor clutch harness connector. Connect a test light between A/C compressor clutch ignition feed circuit (Dark Green wire) and compressor ground circuit (Black wire). If test light comes on, go to next step. If test light does not come on, go to step 18).
  17. Check for poor connections at A/C compressor clutch. Repair as necessary. Go to step 30). If no problem is found, go to step 26).
  18. Check for an open or short to ground in A/C compressor clutch ignition feed circuit (Dark Green wire). Repair as necessary. Go to step 30). If no problem is found, go to step 27).
  19. Turn ignition on. Turn A/C off. Observe A/C REQUEST display on scan tool. If A/C REQUEST displays YES, go to next step. If A/C REQUEST does not display YES, go to step 22).
  20. Turn ignition off. Disconnect PCM harness connector C1. Turn ignition on, A/C off. Using a voltmeter, measure voltage between ground and PCM harness connector C1, terminal No. 62. If reading is near battery voltage, go to next step. If reading is not as specified, go to step 28).
  21. Turn ignition off. Disconnect A/C control head. Turn ignition on. Check A/C request circuit for a short to power. Repair as necessary. Go to step 30). If no problem is found, diagnose A/C controls.
  22. Disconnect A/C relay. Start engine and observe A/C compressor clutch. If A/C compressor clutch is engaged, go to next step. If A/C compressor clutch is not engaged, go to step 25).
  23. Locate and repair short to power in A/C compressor clutch ignition feed circuit (Dark Green wire). Go to step 30).
  24. Repair open or short to ground in circuit No. 1239 (A/C relay ignition feed). Go to step 30).
  25. Replace A/C compressor relay. Go to step 30).
  26. Replace A/C compressor clutch coil. Go to step 30).
  27. Locate and repair open in A/C compressor clutch ground circuit (Black wire). Go to step 30).
  28. Replace PCM. Go to step 30).
  29. Replace A/C refrigerant pressure sensor. Go to next step.
  30. Ensure ambient air temperature is greater than 41°F (5°C), A/C pressure is greater than 96°F (36°C), and coolant temperature is less than 250°F (121°C). Start engine and let idle. Turn A/C on. Listen for engagement of A/C compressor clutch. If A/C compressor clutch engages, system is okay. If A/C compressor clutch does not engage, go to step 3).

Cooling Fan Circuit Diagnosis

  1. If Powertrain On-Board Diagnostic (OBD) System Check has not been performed, see the «BASIC TESTING - 3.1L»(ref-20651) 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 - 3.1L»(ref-20533) 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. Start engine. If cooling fans run, go to step 32). If cooling fans do not run, go to next step.
  4. 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).
  5. Using scan tool, select RELAY CONTROL function. Command high speed fans on. Wait 20 seconds. If both cooling fans operate at high speed, go to next step. If not, 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 both cooling fans come on, go to DIAGNOSTIC AIDS. If both 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 appropriate A/C CLUTCH CIRCUIT DIAGNOSIS TEST in «A/C COMPRESSOR CLUTCH CONTROLS»(ref-20534-S40205641322001010200000) .
  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 mode control relay 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. 504 (White wire). Go to step 81).
  13. Check circuit No. 532 (Gray wire) for a short to ground. Repair as necessary and 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. Locate and repair short to power in circuit No. 504 (White wire), or circuit No. 532 (Gray wire). Go to step 81). If no problem was found, go to step 79).
  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. 30. If test light comes on, go to step 18). If test light does not come on, go to next step.
  17. Check for blown COOL FAN fuse No. 1 (30-amp) 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. 409 or 742. If fuse is not blown, check for an open in power feed circuit No. 742 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. Identify cause of no battery voltage to No. 1 cooling fan relay cavity No. 86. Possible causes are: Open or short in circuit No. 440. Short in No. 1 or No. 2 cooling fan relay coils. Short in mode control relay coil. Repair as necessary. Go to step 81).
  20. Turn ignition off. Disconnect both cooling fan harness connectors. Using fused jumper wires, connect terminals "A" and "B" together at both harness connectors. 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 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 mode control relay from underhood electrical center. Using a test light connected to ground, probe mode control relay 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 mode control relay 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. 504 (White wire) between mode control relay cavity No. 30 and harness connector terminal "A" at cooling fan motor No. 1. Repair as necessary. Go to step 81). If no problem was found, go to step 57).
  30. Check for poor connections at mode control relay cavities No. 30 or 87A in underhood electrical center. Repair as necessary. Go to step 81). If no problem was found, go to step 70).
  31. Check for an open in circuit No. 409 (Light Blue wire) between No. 1 cooling fan relay cavity No. 87 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»(ref-20534-S40205641322001010200000) . 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. 409 (Light Blue 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 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 on scan tool 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 (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 a 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 mode control 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 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 55).
  54. Locate and repair short to power in circuit No. 532 (Gray wire) between mode control relay and cooling fan motor No. 2. Go to step 81).
  55. Locate and repair short to ground in circuit No. 473 (Dark Blue wire) between mode control relay, No. 2 cooling fan relay and PCM. After repair, go to step 81).
  56. Check for an open in circuit No. 504 (White wire) between mode control relay cavity No. 30 and cooling fan motor No. 1, harness connector terminal "A". Repair as necessary. Go to step 81). If no problem was found, go to step 79).
  57. Check for an open in circuit No. 450 (Black wire) between cooling fan motor No. 2, harness connector terminal "A" and ground. Check for an open in circuit No. 532 (Gray wire) between mode control relay cavity No. 87A and cooling fan motor No. 2, harness connector terminal "B". Repair as necessary. Go to step 81). If no problem was found, go to step 80).
  58. Turn ignition on. Remove mode control relay from underhood electrical center. Connect a test light between mode control 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 No. 2 cooling fan relay from underhood electrical center. Connect a test light between No. 2 cooling fan relay cavity No. 85 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. Turn ignition on. Check mode control relay and No. 2 cooling fan relay control circuit (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 mode control relay. Disconnect both cooling fan motor harness connectors. Turn ignition on. Using scan tool, select RELAY CONTROL function. Command high speed cooling 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. Remove mode control relay from underhood electrical center. Using a test light connected to ground, probe mode control 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 mode control relay. Go to step 81).
  66. Using a test light connected to ground, probe mode control 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 circuit No. 504 (White wire) between mode control relay cavity No. 30 and cooling fan motor No. 1, harness connector terminal "A". Go to step 81).
  68. Check for open in circuit No. 532 (Gray wire) between cooling fan motor No. 2 harness connector terminal "B" and mode control relay cavity No. 87A. Repair as necessary. Go to step 81). If no problem was found, go to next step.
  69. Check for poor connections at mode control relay in underhood electrical center. Repair as necessary. Go to step 81). If no problem was found, go to next step.
  70. Replace mode control relay. Go to step 81).
  71. Remove No. 2 cooling fan relay from underhood electrical center. Using a test light connected to ground, probe No. 2 cooling fan relay cavity No. 86. 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 No. 2 cooling fan relay cavity No. 86. Go to step 81).
  73. Using a test light connected to battery positive, probe No. 2 cooling fan relay cavity No. 85. 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. 473 (Dark Blue wire) between No. 2 cooling fan relay cavity No. 85 and PCM harness connector C1, terminal No. 31. Go to step 81).
  75. 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 step 76).
  76. Replace No. 2 cooling fan relay. Go to step 81).
  77. Replace PCM. Go to step 81).
  78. Repair open in circuit No. 473 (Dark Blue wire) between mode control relay cavity No. 86 and No. 2 cooling fan relay cavity No. 85. After repair, 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 below 212°F (100°C). Turn A/C off. Start engine and let idle. If cooling fans run, go to step 32). If cooling fans do not run, 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).

Diagnostic Aids

Check for poor connections at PCM, cooling fan relays and cooling fan motors. Inspect harness connectors for damaged, corroded or backed-out terminal pins. Inspect related wiring harnesses for damage or improper routing.

More articles — Engine System Testing & Engine Component Testing - 3.1L