Engine Controls - System/component Tests 3.8L: Diagnosis Oldsmobile Eighty-Eight X

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.

Injector Balance Test (C-2)

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 INJECTOR BALANCE TEST should not be repeated more than once without starting and running engine.

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. If fuel pressure range is not as specified, see BASIC FUEL SYSTEM CHECKS in BASIC TESTING 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 BASIC TESTING 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 TESTS W/O CODES article.

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" 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 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).

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.

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 PCM or Heating, Ventilation or A/C (HVAC) Diagnostic Trouble Codes (DTCs) have been present. If any DTCs are present, diagnose that code first. See TESTS W/CODES article. If no DTCs are present, go to next step.
3. Ensure intake air temperature is greater than 60°F (15°C). Ensure engine coolant temperature is less than 246°F (119°C). Turn A/C off. Start and idle engine. Observe A/C compressor. If A/C compressor clutch is engaged, go to step 21). If A/C compressor clutch is not engaged, go to next step.
4. Run engine at 1000-1500 RPM. Select DEFROST or MAX mode on A/C control head. Observe A/C compressor. If A/C compressor clutch is engaged, system is operating correctly. Problem may be intermittent. If A/C compressor clutch is not engaged, go to next step.
5. With DEFROST or MAX mode still selected, observe A/C REQUEST display on scan tool. 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. Turn ignition on. With DEFROST or MAX mode still selected, measure voltage on A/C request circuit at PCM harness connector (Dark Green/White wire). 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 (Dark Green/White wire) for an open, short to ground, or poor connection at A/C control head. If a problem was found, diagnose A/C control. If a problem is not found, go to step 37).
8. Check A/C request circuit (Dark Green/White wire) for a poor connection at PCM. If a repair was made, go to step 37). If a repair was not made, go to step 35).
9. Observe A/C refrigerant pressure sensor display on scan tool. If indicated pressure is .35-4.27 volts, go to step 12). If indicated pressure is not .35-4.27 volts, go to next step.
10. Connect Manifold Gauge Set (J 39183-C). Observe high side refrigerant pressure on gauge. If high side refrigerant pressure is within 34-414 psi (2.3-29 kg/cm 2 ), go to next step. If high side refrigerant pressure is not within 34-414 psi (2.3-29 kg/cm 2 ), charge A/C system.
11. Turn ignition off. Disconnect PCM and A/C refrigerant pressure sensor. Measure resistance of following circuits between PCM and A/C refrigerant pressure sensor: Refrigerant pressure sensor signal circuit (Red/Black wire). 5-volt reference "B" circuit (Gray wire). Sensor ground circuit (Black wire). If any resistance is higher than 5 ohms, locate and repair cause of high resistance in circuit as necessary, then go to step 37). If any resistance is not higher than 5 ohms, go to step 18).
12. Disconnect A/C relay electrical connector. Probe ignition feed circuits (Orange and Dark Green wires) at A/C relay harness connector with a test light to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 31).
13. Connect a fused jumper between ignition feed circuit and A/C compressor clutch control circuit (Dark Green wire) at A/C relay connector. If A/C compressor clutch engages, go to step 14). If A/C compressor clutch does not engage, go to step 15).
14. Check for poor connections at A/C relay. If a repair was made, go to step 37). If a repair was not made, go to step 32).
15. Disconnect A/C compressor clutch electrical connector (leave ignition feed circuit and A/C compressor clutch control circuit jumpered at A/C relay connector). Connect a test light between A/C compressor clutch control circuit (Dark Green wire) and compressor ground circuit (Black wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 17).
16. Check for poor connections at A/C compressor clutch. If a repair was made, go to step 37). If a repair was not made, go to step 33).
17. Check for an open or short to ground in A/C compressor clutch control circuit (Dark Green wire). If a repair was made, go to step 37). If a repair was not made, go to step 34).
18. Leave PCM and A/C refrigerant pressure sensor disconnected at PCM. Turn ignition on. Measure voltage between A/C refrigerant pressure signal circuit (Red/Black wire) and ground. If voltage is about zero volts, go to next step. If voltage is not about zero volts, go to step 20).
19. Check the following: 5-volt reference "B" circuit (Gray wire) for a poor connection at PCM. 5-volt reference "B" circuit (Gray wire) for a poor connection at refrigerant pressure sensor. Refrigerant pressure signal circuit (Red/Black wire) for a poor connection at PCM. Refrigerant pressure signal circuit (Red/Black wire) for a poor connection at refrigerant pressure sensor. Sensor ground circuit (Black wire) for a poor connection at refrigerant pressure sensor. If a problem is found, repair as necessary and go to step 37). If a problem was not found, go to step 36).
20. Locate and repair short to voltage in A/C refrigerant pressure signal circuit (Red/Black wire). Go to step 37).
21. Turn ignition on. Turn A/C off. Observe A/C REQUEST on scan tool. If A/C REQUEST displays YES, go to next step. If A/C REQUEST does not display YES, go to step 24).
22. Turn ignition off. Disconnect PCM. Turn ignition on, A/C off. Measure voltage between A/C request circuit (Dark Green/White wire) at PCM harness connector and ground. If voltage measures near battery voltage, go to next step. If voltage does not measure near battery voltage, go to step 35).
23. Turn ignition off. Disconnect A/C control head/programmer. Turn ignition on. Check A/C request circuit (Dark Green/White wire) for a short to voltage. If a problem was found and a repair was made, go to step 37). If a problem was not found, diagnose A/C controls.
24. Disconnect A/C relay. Start vehicle and observe A/C compressor. If A/C compressor clutch is engaged, go to step 29). If A/C compressor clutch is not engaged, go to next step.
25. Probe A/C compressor clutch control circuit (Dark Green wire) at A/C relay harness connector with a test light to ground. If test light illuminates, go to step 27). If test light does not illuminate, go to next step.
26. Replace A/C relay. Go to step 37).
27. Turn ignition off. Disconnect PCM. Probe A/C relay driver circuit (Dark Green/White wire) at PCM connector with a test light connected to battery voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 35).
28. Repair short to ground in A/C compressor clutch relay driver circuit (Dark Green/White wire). Go to step 37).
29. Turn ignition off. Disconnect A/C compressor clutch electrical connector. Start engine and observe A/C compressor. If A/C compressor clutch is engaged, go to step 33). If A/C compressor clutch is not engaged, go to next step.
30. Locate and repair short to voltage in A/C compressor clutch control circuit (Dark Green wire). Go to step 37).
31. Repair open or short to ground in ignition feed circuit (Pink wire) to A/C compressor relay. Go to step 37).
32. Replace A/C compressor relay. Go to step 37).
33. Repair A/C compressor clutch. Go to step 37).
34. Locate and repair open in A/C compressor clutch ground circuit (Black wire). Go to step 37).
35. Replace PCM. Go to step 37).
36. Replace A/C refrigerant pressure sensor. Go to step 37).
37. Ensure intake air temperature is greater than 60°F (15°C). Ensure engine coolant temperature is less than 246°F (119°C). With A/C off, start and idle engine. Observe A/C compressor. If clutch is engaged, go to step 21). If clutch is not engaged, go to next step.
38. Run engine at 1000-1500 RPM. Select DEFROST or MAX mode on control head. Observe A/C compressor. If A/C compressor clutch is engaged, system is okay. If A/C compressor clutch is not engaged, go to step 5).

Cooling Fan 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 for PCM Diagnostic Trouble Codes (DTCs). If any codes are present, perform testing for applicable code. Some DTCs will cause fans to come on at all times, so repair all DTCs that are present before proceeding with testing. See TESTS W/CODES article. If no codes are present, go to next step.
3. Ensure coolant temperature is less than 212°F (100°C). Turn A/C off. Ensure engine is running. If cooling fans are running, go to step 30). If cooling fans are not running, go to next step.
4. Using scan tool OUTPUT TESTS, command fan No. 1 on. If both fans run at low speed, go to next step. If both fans do not run at low speed, go to step 8).
5. Using scan tool OUTPUT TESTS, command fan No. 2 on. If left fan runs at high speed, go to next step. If left fan does not run at high speed, go to step 18).
6. Ensure ambient temperature is greater than 60°F (15°C). Exit scan tool output tests. Turn engine on and leave running. Turn A/C on. If fans come on, system is operating properly, but problem may be intermittent. If fans do not come on, go to next step.
7. Using scan tool, display A/C REQUEST. If scan tool displays YES, go to step 44). If scan tool displays NO, check A/C clutch for problem.
8. Disconnect low speed cooling fan relay. Turn ignition on. Probe low speed cooling fan relay harness connector terminal No. 85 (Brown wire) with a test light connected to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 28).
9. Probe low speed cooling fan relay harness connector terminal No. 30 (Red wire) with a test light to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 29).
10. Connect fused jumper between low speed cooling fan relay harness connector terminals No. 87 (Light Blue wire) and No. 30 (Red wire). If both cooling fans run at low speed, go to next step. If both cooling fans do not run at low speed, go to step 14).
11. Using scan tool OUTPUT CONTROL function, select fan No. 1 and command fans on. Probe low speed cooling fan harness connector terminal No. 86 (Dark Green wire) with a test light to voltage. If test light illuminates, go to step 40). If test light does not illuminate, go to step 12).
12. Turn ignition off. Disconnect PCM. Turn ignition on. Check low speed cooling fan relay driver circuit for an open or short to voltage between PCM and low speed cooling fan relay. If a problem is found, repair as necessary, then go to step 46). If a problem is not found, go to next step.
13. Check low speed cooling fan relay driver circuit for a poor terminal connection at PCM. If a problem is found, repair as necessary, then go to step 46). If a problem is not found, go to step 44).
14. Disconnect both cooling fan motors. Leave low speed cooling fan relay connector terminals No. 87 and 30 jumpered. Probe terminal "B" (Black or Light Blue wire) at both fan motor connectors with a test light to ground. If test light illuminates at both fan connectors, go to step 45). If test light does not illuminate at both fan connectors, go to step 16).
15. Connect test light between terminals "A" (Light Blue or Black wire) and "B" (Light Blue or Black wire) at both cooling fan connectors. If test light illuminates at both fan connectors, go to step 45). If test light does not illuminate at both fan connectors, go to step 17).
16. Locate and repair open circuit in Black or Light Blue wire. Go to step 46).
17. Locate and repair open in ground circuit to affected cooling fan motors(s). Go to step 46).
18. Disconnect high speed cooling fan relay. Turn ignition on. Probe high speed cooling fan relay harness connector terminal No. 30 (Red wire) with a test light to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 29).
19. Probe high speed cooling fan relay harness connector terminal No. 86 (Dark Blue wire) with a test light to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 28).
20. Connect fused jumper between high speed cooling fan relay harness connector terminals No. 30 (Red wire) and No. 87 (Black wire). If left cooling fan runs at high speed, go to next step. If left cooling fan does not run at high speed, go to step 24).
21. Using scan tool OUTPUT CONTROL function, select fan No. 2 and command fan on. Probe high speed cooling fan harness connector terminal No. 86 (Dark Blue wire) with a test light to voltage. If test light illuminates, go to step 42). If test light does not illuminate, go to next step.
22. Turn ignition off. Disconnect PCM. Turn ignition on. Check high speed cooling fan relay driver circuit for an open or short to voltage between PCM and high speed cooling fan relay. If a problem is found, repair as necessary, then go to step 46). If a problem is not found, go to next step.
23. Check high speed cooling fan relay driver circuit for a poor terminal connection at PCM. If a problem is found, repair as necessary, then go to step 46). If a problem is not found, go to step 44).
24. Disconnect left side cooling fan motor connector (leave high speed cooling fan relay harness connector terminals No. 30 and 87 jumpered). Probe left side cooling fan motor harness connector terminal "B" (Black wire) with a test light to ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 27).
25. Connect test light between left side cooling fan motor harness connector terminals "A" and "B" (Black and Light Blue wires). If test light illuminates, go to step 45). If test light does not illuminate, go to next step.
26. Locate and repair open in ground circuit to left side cooling fan motor. Repair as necessary, then go to step 46).
27. Locate and repair open in Black wire to left side cooling fan. Go to step 46).
28. Locate and repair open in ignition feed circuit (Brown wire) to left side cooling fan. Go to step 46).
29. Locate and repair open in battery feed circuit (Red wire) to affected cooling fan relay. Go to step 46).
30. Disconnect high speed cooling fan relay. If either cooling fan is on, go to step 35). If either cooling fan is not on. go to step 31).
31. Probe high speed cooling fan relay harness connector terminal No. 86 (Dark Blue wire) with a test light to voltage. If test light illuminates, go to next step. If test light is not illuminated, go to step 43).
32. Observe A/C refrigerant pressure on scan tool. If A/C refrigerant pressure is greater than 260 psi (18.2 kg/cm 2 ), problem is with A/C system. Diagnose A/C-heater system. If pressure is less than 260 psi (18.2 kg/cm 2 ), go to next step.
33. Turn ignition off. Disconnect PCM. Turn ignition on. Probe high speed cooling fan relay harness connector terminal No. 86 (Dark Blue wire) to voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 44).
34. Locate and repair short to ground in high speed cooling fan relay driver circuit. Go to step 46).
35. Disconnect low speed cooling fan relay. If either cooling fan is on, go to step 39). If either cooling fan is not on, go to step 36).
36. Probe low speed cooling fan relay harness connector terminal No. 86 (Dark Green wire) with a test light to voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 41).
37. Turn ignition off. Disconnect PCM. Turn ignition on. Probe low speed cooling fan relay harness connector terminal No. 86 (Dark Green wire) with a test light to voltage. If test light illuminates, go to next step. If test light does not illuminate, go to step 44).
38. Locate and repair short to ground in low speed cooling fan relay driver circuit. Go to step 46).
39. Locate and repair short to voltage in affected cooling fan feed circuit. (Light Blue or Black wire). Go to step 46).
40. Check for poor connection at low speed cooling fan relay. If problem is found, repair as necessary, then go to step 46). If a problem is not found, go to step 43).
41. Replace high speed cooling fan relay. Go to step 46).
42. Check for poor connection at high speed cooling fan relay. If a problem is found, repair as necessary, then go to step 46). If a problem is not found, go to next step.
43. Replace high speed cooling fan relay. Go to step 46).
44. Replace PCM. Go to step 46).
45. Replace affected cooling fan motor. Go to step 46).
46. Ensure engine coolant temperature is less than 212°F (100°C). Turn A/C off. Leave engine running. If cooling fans operate, go to step 30). If cooling fans do not operate, go to next step.
47. Using scan tool OUTPUT TESTS, command fan No. 1 on. If both fans run at low speed, go to step 48). If both fans do not run at low speed, go to step 8).
48. Using scan tool OUTPUT TESTS, command fan No. 2 on. If left side fan runs at high speed, system is operating normally at this time. If left side fan does not run at high speed, go to step 18).

Scheme 33

Scheme 34