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Engine Controls - System/component Tests 4.0L: Diagnosis Oldsmobile Aurora I

Testing & Diagnostics 2 illustrations ~3968 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.Move A/C mode selector 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 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

Connect Tech 1 scan tool and select "Inj. Balance" test. Start engine. Record change in engine speed and idle quality as each cylinder is disabled. Engine speed and idle quality changes should be equal for all cylinders. If changes are not equal, check ignition system or perform further diagnostics. See TESTS W/O CODES or TESTS W/CODES article.

CAUTIONTo avoid possible vehicle fire, wrap shop towel around fitting to absorb fuel spillage.

Injector Flow/Voltage Drop Test

  1. Ensure all Diagnostic Trouble Codes (DTC) are cleared. Turn ignition off. Install Fuel Pressure Gauge (J-34730-1A). Connect Tech 1 scan tool.
  2. Turn ignition on. Using scan tool, select "Misc Tests" then select "Output Tests" and then "FP Relay" to energize fuel pump. Note fuel pressure. Connect Fuel Injector Tester (J-39021) to injector No. 1, select "Fuel Injector Flow Test" to test injector. Note fuel pressure and subtract reading from previous fuel pressure reading. Perform the same test to all injectors.
  3. If fuel pressure drops when each injector is tested, go to step 5). If fuel pressure does not drop in any one of injector during test, go to next step. If pressure in only one injector did not drop during test, go to step 8).
  4. Turn ignition off. Inspect fuel injector fuses No. 1 and 2, located in passenger compartment fuse block. If fuses are okay, go to next step. If fuses are faulty, check for shorted circuit between fuse block and fuel injector harness connector. Repair as necessary.
  5. Disconnect fuel injector harness connector. Turn ignition on. Using DVOM, check voltage between ground and harness connector terminals "N" and "P". If both terminals measure greater than 10 volts, go to step 10). If both terminals measure less than 10 volts, check or repair open in circuits No. 739 and 1239, between fuse block and fuel rail harness connector. (Scheme 22)
  6. Using Fuel Injector Tester (J-39021), select "Coil Test" and test all injectors. Voltage reading should be 9.5 volts. If voltage reading in any of injectors is greater than 9.5 volts, replace fuel injector. If voltage reading in any of injectors is less than 9.5 volts, go to next step.
  7. Subtract highest voltage reading from specified voltage. If voltage difference is greater than.55 volts of highest injector voltage reading, replace injector.
  8. Using Fuel Injector Tester, select "Coil Test" and test injector that did not have fuel pressure drop. Injector coil test should read 5.7-7.0 volts. If voltage is as specified, go to next step. If voltage is not as specified, check fuel injector harness connector for open or shorted circuit to affected injector.
  9. Reconnect fuel injector harness connector. Disconnect PCM connector C2. Turn ignition on. Using DVOM, check voltage between ground and PCM connector terminal of suspect injector. (Scheme 22) DVOM should read about 10 volts. If voltage is as specified, check PCM terminal contact or replace faulty PCM. If reading is greater than 10 volts, repair open between fuel injector harness connector and PCM circuit to affected injector.
  10. Check resistance of suspect fuel injector. Resistance should be 8-25 ohms. If resistance is as specified, go to next step. If resistance is not as specified, go to step 9).
  11. Connect Fuel Injector Tester to suspect fuel injector and select "Coil Test". Reading should be 5.7-7.0 volts. If voltage reading is as specified, repair fuel injector harness of suspect injector. If voltage reading is not as specified, replace suspect injector.

Scheme 22

Scheme 22
Scheme 22

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" tester 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»(ref-20351-S22118861902001010200000) table or INJECTOR BALANCE TEST (C2).
  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 INJECTOR BALANCE TEST (C2).
ApplicationVolts
4.0L5.7-7.0

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 BASIC TESTING article. After performing OBD system check, go to next step.
  2. Check instrument cluster. See 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 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 found, 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 "Outputs Test" 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).

C-10 & C-12 DIAGNOSTIC TESTS

Note. For a more specific system testing, refer to the following C-10 and C-12 diagnostic tests. If any test other than a C-10 or C-12 test is referenced, see TESTS W/CODES article.

Compressor Clutch Control Circuit Diagnosis

  1. Perform On-Board Diagnostics (OBD) System check. See BASIC TESTING article. After performing OBD system check, go to next step.
  2. Check if any Diagnostic Trouble Codes (DTCs) are stored. If any DTCs are present, perform diagnosis for codes first. See TESTS W/CODES article. If no DTCs are present, go to next step.
  3. Ensure ambient temperature is greater than -10°F (-23°C). With A/C off, start and idle engine. Observe A/C compressor clutch. If compressor clutch is engaged, go to step 10). If clutch is not engaged, go to step 4).
  4. With engine idling and A/C on for more than 30 seconds, check compressor clutch. If compressor clutch is engaged, system is okay. If clutch is not engaged, go to next step.
  5. Turn ignition off. Connect scan tool. Turn ignition on. With A/C still on, observe A/C relay control circuit in ENGINE 3 DATA VALUES. If scan tool displays OKAY, go to next step. If scan tool does not display OKAY, go to step 12).
  6. Remove A/C relay. With a test light connected to ground, check terminals No. 30 (Pink wire) and 85 (Pink wire) in A/C relay cavity. If test light illuminates on both terminals, go to next step. If test light does not illuminate on both terminals, go to step 14).
  7. With a fused jumper wire, connect terminals No. 30 (Pink wire) and No. 87 (Dark Green wire) in A/C relay cavity. Observe A/C compressor clutch. If A/C compressor clutch is engaged, go to step 15). If A/C compressor clutch is not engaged, go to next step.
  8. Disconnect A/C compressor clutch connector. Measure resistance between terminal No. 87 (Dark Green wire) in A/C relay cavity to terminal "A" (Dark Green wire) of A/C compressor clutch connector. If resistance is less than 5 ohms, go to next step. If resistance 5 ohms or greater, go to step 16).
  9. Measure resistance between A/C compressor clutch connector terminal "B" (Black wire) and ground. If resistance is less than 5 ohms, PCM circuits are okay. If resistance is 5 ohms or greater, go to step 25).
  10. Turn ignition off. Connect scan tool. Turn ignition on. Observe A/C relay control circuit in ENGINE 3 DATA VALUES. If scan tool displays ON, go to next step. If scan tool does not display ON, go to step 17).
  11. Disconnect PCM connector C1. Check for poor terminal contact at connector C1, terminal No. 27 (Dark Green/White wire). If a repair was made, go to step 18). If a repair was not made, go to step 24).
  12. Remove A/C relay. Measure voltage between A/C relay terminal No. 86 (Dark Green/White wire) and ground. If voltage is greater than .3 volt, go to step 17). If voltage is .3 volt or less, go to step 13).
  13. Disconnect PCM connector C1. Measure resistance between terminal No. 86 (Dark Green/White wire) in A/C relay cavity to PCM connector C1, terminal No. 27 (Dark Green/White wire). If resistance is less than5 ohms, go to next step. If resistance is 5 ohms or greater, go to step 19).
  14. If test light illuminates at either terminal, go to step 20). If test light does not illuminate, go to step 21).
  15. Check terminal contact at A/C relay. If a terminal contact problem is found, go to step 18). If a terminal contact problem is not found, go to step 22).
  16. Check terminal contact at A/C compressor clutch connector. If a terminal contact problem is found, go to step 18). If a terminal contact problem is not found, go to step 23).
  17. Repair short to voltage in Dark Green/White wire.
  18. Repair terminal contact.
  19. Repair open in Dark Green/White wire.
  20. Repair Pink wire between splice and terminal where test light did not illuminate.
  21. Check for an open in Pink wire between fuse and splice, short in Dark Green wire (blown fuse), shorted relay (blown fuse), or short in Pink wire (blown fuse).
  22. Replace A/C relay.
  23. Repair open in Dark Green wire.
  24. Replace PCM.
  25. Repair open in Black Ground wire.

Cooling Fan Symptom Check No. 1

  1. If COOLING FAN FUNCTIONAL CHECK has been performed, go to next step. If COOLING FAN FUNCTIONAL CHECK has not been performed, go to next step.
  2. Disconnect cooling fan No. 1 connector. Using scan tool, select MISC. TESTS, then OUTPUT TESTS, then FAN RELAYS. With key on, command fan relay No. 1 on. Using a DVOM, measure voltage to ground at cooling fan No. 1 harness connector terminal "B" (Black wire). If voltage is less than 10 volts, go to next step. If voltage is 10 volts or greater, go to step 6).
  3. Jumper cooling fan No. 1 connector terminals "A" (White wire) and "B" (Black wire) together. If cooling fan No. 2 operates while jumpered, go to step 8). If cooling fan No. 2 does not operate while jumpered, go to next step.
  4. With cooling fan No. 1 harness connector still jumpered, remove relay No. 2. Measure voltage to ground at relay No. 2, terminal No. 30 (Light Blue wire). If voltage is 10 volts or greater, go to next step. If voltage is less than 10 volts, go to step 9).
  5. Jumper relay No. 2 terminal No. 30 (Light Blue wire) and relay No. 3, terminal 87A (Light Blue wire). If cooling fan No. 2 operates with relay jumpered, go to step 10). If cooling fan No. 2 does not operate with relay jumpered, go to step 11).
  6. Exit FAN RELAYS. Remove relay No. 1. Measure voltage to ground at relay No. 1, terminal No. 30 (Orange or Brown wire). If voltage is 10 volts or greater, go to step 13). If voltage is less than 10 volts, go to step 14).
  7. Jumper fan relay No. 1 terminals No. 30 (Orange or Brown wire) and No. 87 (Black wire) together. Measure voltage to ground at cooling fan No. 1 connector terminal "B" (Black wire). If voltage is 10 volts or greater, go to step 13). If voltage is less than 10 volts, go to step 14).
  8. Replace cooling fan No. 1. Go to COOLING FAN FUNCTIONAL CHECK.
  9. Repair open circuit in White wire between cooling fan No. 1 and fan relay No. 2. Go to COOLING FAN FUNCTIONAL CHECK.
  10. Replace fan relay No. 2. Go to COOLING FAN FUNCTIONAL CHECK.
  11. Repair open circuit in Light Blue wire between fan relay No. 2 and splice. Go to COOLING FAN FUNCTIONAL CHECK.
  12. Repair open circuit in Red wire between fan relay No. 1 and 60-amp fuse. Go to COOLING FAN FUNCTIONAL CHECK.
  13. Replace fan relay No. 1. Go to COOLING FAN FUNCTIONAL CHECK.
  14. Repair open circuit in Black wire between fan relay No. 1 and cooling fan No. 1. Go to COOLING FAN FUNCTIONAL CHECK.

Cooling Fan Symptom Check No. 2

  1. If COOLING FAN FUNCTIONAL CHECK was performed, go to next step. If COOLING FAN FUNCTIONAL CHECK was not performed, go to COOLING FAN FUNCTIONAL CHECK.
  2. Disconnect cooling fan No. 2 connector. Using scan tool, select MISC. TESTS, then OUTPUT TESTS, then FAN RELAYS. With key on, command FAN RELAY No. 1 on. Jumper cooling fan No. 2 terminals "A" (Black wire) and "B" (Light Blue wire) together. If cooling fan No. 1 operates, go to step 5). If cooling fan No. 1 does not operate, go to next step.
  3. With FAN RELAY No. 1 still commanded on, remove fan relay No. 2. Jumper fan relay No. 2 terminals No. 30 (Light Blue wire) and 87A (Light Blue wire) together. If cooling fan operates with relay jumpered, go to step 6). If cooling fan does not operate with relay jumpered, go to next step.
  4. With fan relay No. 2 still jumpered, measure voltage to ground at cooling fan No. 2 connector terminal "B" (Light Blue wire). If voltage is 10 volts or more, go to step 7). If voltage is not 10 volts or more, go to step 8).
  5. Replace cooling fan No. 2. Go to COOLING FAN FUNCTIONAL CHECK.
  6. Replace fan relay No. 2. Go to COOLING FAN FUNCTIONAL CHECK.
  7. Repair open circuit in Black wire between cooling fan No. 2 and splice. Go to COOLING FAN FUNCTIONAL CHECK.
  8. Repair open circuit in Light Blue wire between cooling fan No. 2 and splice and fan relay No. 2. Go to COOLING FAN FUNCTIONAL CHECK.

Cooling Fan Symptom Check No. 3

  1. If COOLING FAN FUNCTIONAL CHECK was performed, go to next step. If COOLING FAN FUNCTIONAL CHECK was not performed, go to COOLING FAN FUNCTIONAL CHECK.
  2. Using scan tool, select MISC. TESTS, then OUTPUT TESTS, then FAN RELAYS. With key on, select all relays on. Remove fan relay No. 2. Measure voltage to ground at fan relay No. 2, terminal No. 85 (Orange or Brown wire). If voltage is 10 volts or more. go to next step. If voltage is not 10 volts or more, go to step 5).
  3. Remove fan relay No. 3. Measure resistance between fan relay No. 2, terminal No. 86 (Dark Blue wire) and fan relay No. 3, terminal No. 86 (Dark Blue wire). If resistance is 5 ohms or less, go to next step. If resistance is not 5 ohms or less, go to step 6).
  4. Reconnect fan relay No. 3. With all relays still commanded on, jumper fan relay No. 2 terminals No. 30 (Light Blue wire) and No. 87 (Red wire). If both cooling fans operate with relay jumpered, go to step 8). If both cooling fans do not operate while jumpered, go to step 7).
  5. Repair open circuit in Orange or Brown wire between fan relay No. 2, terminal No. 85 and splice. Go to COOLING FAN FUNCTIONAL CHECK.
  6. Repair open circuit in Dark Blue wire between fan relay No. 2, terminal No. 86 and splice. Go to COOLING FAN FUNCTIONAL CHECK.
  7. Repair open circuit in Red wire between fan relay No. 2, terminal No. 87 and splice. Go to COOLING FAN FUNCTIONAL CHECK.
  8. Replace fan relay No. 2. Go to COOLING FAN FUNCTIONAL CHECK.

Cooling Fan Symptom Check No. 4

  1. If COOLING FAN FUNCTIONAL CHECK was performed, go to next step. If COOLING FAN FUNCTIONAL CHECK was not performed, go to COOLING FAN FUNCTIONAL CHECK.
  2. Using scan tool, select MISC. TESTS, then OUTPUT TESTS, then all relays. With key on, command all relays on. Remove fan relay No. 3. Measure voltage to ground at fan relay No. 3, terminal No. 85 (Orange or Brown wire). If voltage is 10 volts or more, go to next step. If voltage is not 10 volts or more, go to step 6).
  3. Measure voltage to ground at fan relay No. 3, terminal No. 30 (White wire). If voltage is 10 volts or more, go to next step. If voltage is not 10 volts or more, go to step 7).
  4. Remove fan relay No. 3. Measure resistance between fan relay No. 3, terminal No. 86 (Dark Blue wire) and fan relay No. 2, terminal No. 86 (Dark Blue wire). If resistance is 5 ohms or less, go to next step. If resistance is not 5 ohms or less, go to step 8).
  5. Reconnect fan relay No. 2. With all relays still commanded on, jumper fan relay No. 3, terminals No. 30 (White wire) and No. 87 (Black wire). If cooling fan No. 2 operates with relay jumpered, go to step 10). If cooling fan No. 2 does not operate with relay jumpered, go to step 9).
  6. Repair open circuit in wiring between fan relay No. 3, terminal No. 30 (White wire) and Blue maxi-fuse (60-amp). Go to COOLING FAN FUNCTIONAL CHECK.
  7. Repair open circuit in Orange or Brown wire between fan relay No. 3, terminal No. 85 and splice. Go to COOLING FAN FUNCTIONAL CHECK.
  8. Repair open circuit in Dark Blue wire between fan relay No. 3, terminal No. 86 and splice. Go to COOLING FAN FUNCTIONAL CHECK.
  9. Repair open circuit in Black wire between fan relay No. 3, terminal No. 87 and splice. Go to COOLING FAN FUNCTIONAL CHECK.
  10. Replace fan relay No. 3. Go to COOLING FAN FUNCTIONAL CHECK.

Cooling Fan Symptom Check No. 5

  1. If COOLING FAN FUNCTIONAL CHECK was performed, go to next step. If COOLING FAN FUNCTIONAL CHECK was not performed, go to COOLING FAN FUNCTIONAL CHECK.
  2. Check Blue maxi-fuse (60-amp). If fuse is okay, go to next step. If fuse is blown, go to step 4).
  3. Remove fan relay No. 1. Measure voltage between ground and fan relay No. 1 terminal No. 30 (Red wire). If voltage is 10 volts or more, go to step 8). If voltage is not 10 volts or more, go to step 9).
  4. Turn ignition switch to LOCK position. Replace 60-amp fuse. If fuse immediately blows, go to step 10). If fuse does not immediately blow, go to next step.
  5. Turn ignition on. Using scan tool, select MISC. TESTS, then OUTPUT TESTS, then FAN RELAYS. Command FAN RELAY No. 1 on. If 60-amp fuse blows, go to step 11). If 60-amp fuse does not blow, go to next step.
  6. Command all relays on. If 60-amp fuse blows, go to next step. If 60-amp fuse does not blow, system is operating normally at this time.
  7. Exit FAN RELAYS. Replace 60-amp fuse. Select FAN RELAYS and command FAN RELAY No. 1 on. If cooling fan No. 1 operates, go tostep 12). If cooling fan No. 1 does not operate, go to step 13).
  8. Repair open circuit in Black wire between both splices or between splice and ground. Go to COOLING FAN FUNCTIONAL CHECK.
  9. Repair open circuit in Red wire between 60-amp fuse and both relays. Go to COOLING FAN FUNCTIONAL CHECK.
  10. Repair short to ground in Red wire between 60-amp fuse and either fan relay No. 1 or fan relay No. 3. Go to COOLING FAN FUNCTIONAL CHECK.
  11. Repair short to ground in Black wire between fan relay No. 1 and cooling fan No. 1. Go to COOLING FAN FUNCTIONAL CHECK.
  12. Replace cooling fan No. 2. Go to COOLING FAN FUNCTIONAL CHECK.
  13. Replace cooling fan No. 1. Go to COOLING FAN FUNCTIONAL CHECK.

Diagnostic Aids

If cooling fans operate when commanded off and DTC P1660 is not present, either a cooling fan relay is stuck on or a cooling fan circuit is shorted to power. Whenever a repair is completed repeat COOLING FAN FUNCTIONAL CHECK. This will help diagnose possible multiple failures.

Scheme 23

Scheme 23: COMPONENT LOCATIONS
Scheme 23: COMPONENT LOCATIONS

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