Engine Control System - Basic Engine Testing: Other Oldsmobile Silhouette II

Compression

Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions. For compression specifications, see the SPECIFICATIONS article.

Exhaust System Backpressure

Before replacing any components, check exhaust system for restrictions. Use a vacuum gauge or a low-pressure (0-5 psi) gauge to check exhaust system.

If a vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Partially open throttle and hold steady. If vacuum gauge reading slowly drops after stabilizing, exhaust system should be checked for a restriction.

If using a low pressure gauge, connect gauge in the following manner

1. Check At Oxygen Sensor Remove oxygen sensor. Install backpressure tester in place of oxygen sensor. After test is completed, coat oxygen sensor threads with anti-seize compound before installation.

DEFINITION

No-start is defined as engine cranks okay but does not start. Engine may fire a few times.

NO START - ENGINE CRANKS OKAY

Note. Before performing following tests, check battery condition, engine cranking speed and fuel supply.

Ignition System

1. Perform On-Board Diagnostic (OBD) System Check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . After performing OBD system check, go to next step.
2. Install Tech 1 scan tool. Using scan tool, select FAILED SINCE CODE CLEAR function. If Diagnostic Trouble Code (DTC) P0101, P0123, P0601/P0602, P1200, P1374, P1626 or P1629 is present, diagnose DTC. See the «TESTS W/CODES»(ref-20678) article. If DTC(s) are not present, go to next step.
3. Turn ignition on with engine off. Using scan tool, monitor Manifold Absolute Pressure (MAP) sensor. If MAP sensor value is less than 65 kPa, go to step 27). If MAP sensor value is more than 65 kPa, go to next step.
4. Turn ignition off. Disconnect MAP sensor connector. Attempt to start engine. If engine starts and continues to run, go to step 27). If engine does not start, go to next step.
5. Turn ignition off. Reconnect MAP sensor connector. Install fuel pressure gauge. Turn ignition on and observe fuel pressure. Fuel pressure should be 41-47 psi (2.9-3.3 kg/cm 2 ). If fuel pressure is as specified, go to step 7). If fuel pressure is not as specified, go to next step.
6. If fuel pressure is present, but not as specified, diagnose fuel system. See «BASIC FUEL SYSTEM CHECKS»(ref-20674-S29918334612001010200000) . If fuel pressure is not present, go to FUEL SYSTEM.
7. Turn ignition off. Disconnect 10-pin fuel injector/engine harness connector. Using a test light connected to battery voltage, probe each injector driver circuit while cranking engine. If test light flashes, go to next step. If test light does not flash, go to step 9).
8. Remove fuel injection fuse from underhood fuse block. Install Spark Tester (J-26792) to cylinder No. 2, 4 and 6 (one at a time). Connect the spark plug wire of companion cylinder to ground. Crank engine and observe spark tester. If spark is present, go to step 19). If spark is not present, go to step 11).
9. Check fuel injector feed circuit fuse. If fuse is faulty, check for an open or shorted circuit, or shorted injector. Repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If circuit and injector are okay, go to next step.
10. Check for open in fuel injector feed circuit or ignition main relay feed circuits. Check for open in ignition main relay ground circuit. Check for stuck open ignition main relay or corroded contacts. Repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If circuits or relay are okay, testing is complete.
11. Check fuse to Ignition Control Module (ICM) ignition feed circuit. If fuse is faulty, check for short between ICM feed circuit and engine ground, module ground, IC control circuit or reference low circuit. Repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If fuse is okay, go to next step.
12. Check for open in ICM feed and ground circuits. Repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If circuits are okay, go to next step.
13. Disconnect 7X Crankshaft Position (CKP) sensor connector from ICM. Connect DVOM between CKP sensor harness connector terminals. Set DVOM to 2-volt AC scale. Crank engine and observe DVOM. DVOM should read about 2-volts AC. If voltage is as specified, go to step 15). If voltage is not as specified, go to next step.
14. Turn ignition off. Check 7X CKP sensor circuit for open or short to voltage or ground. Check for poor 7X CKP sensor connection. Repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If circuit is okay, go to step 28).
15. Check for poor ICM connection. Repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If connection is okay, go to next step.
16. Remove and inspect coil that did not produce a spark. Check for cracks or carbon tracking. Replace as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If coil(s) are okay, go to next step.
17. Check secondary resistance to ignition coil that did not produce a spark. Resistance should be 5000-7000 ohms. If resistance is not as specified, replace ignition coil. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If coil resistance is as specified, go to next step.
18. Connect a test light across affected ICM primary terminals. Crank engine and observe test light. If test light flashes while cranking engine, go to step 29). If test light does not flash, go to step 30).
19. Check cylinders No. 2, 4 and 6 spark plug wires. Check for carbon tracking or damaged insulation. Replace as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If wire(s) are okay, go to next step.
20. Check spark plug wire resistance of cylinders No. 2, 4 and 6. Resistance should be 7000 ohms. If resistance is not as specified, replace wire(s). After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If wire(s) are okay, go to next step.
21. Remove spark plugs from cylinders No. 2, 4 and 6. Check spark plug electrodes for excessive fouling. If excessive fouling is present, go to step 26). If excessive fouling is not present, go to next step.
22. Check cylinders No. 1, 3 and 5 spark plug wires. Check for carbon tracking or damaged insulation. Replace as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If wire(s) are okay, go to next step.
23. Check spark plug wire resistance of cylinders No. 1, 3 and 5. Resistance should be 7000 ohms. If resistance is not as specified, replace wire(s). After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If wire(s) are okay, go to next step.
24. Remove spark plugs from cylinders No. 1, 3 and 5. Check spark plug electrodes for excessive fouling. If excessive fouling is present, go to step 26). If excessive fouling is not present, go to next step.
25. Test fuel for contamination. If fuel is contaminated, clean fuel system. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If fuel is not contaminated, check for poor or damaged PCM connector, for faulty engine coolant temperature sensor, or mass air flow miscalculated due to faulty throttle position sensor or manifold absolute pressure sensor. See the «SYSTEM/COMPONENT TESTS»(ref-20675) article.
26. Check for engine mechanical problem. Check for bent push rods, faulty camshaft, leaking or sticky valves or rings, excessive valve deposits, loose or worn rocker arms, weak valve springs, incorrect valve timing or leaking head gasket. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
27. Replace MAP sensor. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
28. Replace 7X CKP sensor. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
29. Replace ignition coil(s) associated with cylinder that did not produce a spark. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
30. Replace ICM. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
31. Replace PCM. Perform PCM relearn procedures. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .

Fuel System

1. Perform On-Board Diagnostic (OBD) System Check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . After performing OBD system check, go to next step.
2. Turn ignition off. Install fuel pressure gauge to fuel pressure test port. Connect a fused jumper wire between battery voltage and fuel pump test terminal. Note fuel pressure. Fuel pressure should be 41-47 psi (2.9-3.3 kg/cm 2 ). If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to step 10).
3. Disconnect jumper wire from fuel pump test terminal. Remove fuel pump relay. Connect a test light between fuel pump relay harness connector terminals No. 87 (Red wire) and No. 85 (Black/White wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 9).
4. Turn ignition off. Connect a test light between fuel pump relay harness connector terminals No. 86 (Dark Green/White wire) and No. 85 (Black/White wire). Turn ignition on. Test light should illuminate for about 2 seconds. If test light illuminates as specified, go to step 8). If test light does not illuminate or stays illuminated for greater than 2 seconds, go to next step.
5. Turn ignition off. Disconnect PCM harness connector. Using a test light connected to battery voltage, probe fuel pump relay circuit (Dark Green/White wire) at PCM connector. If test light illuminates, go to step 15). If test light does not illuminate, go to next step.
6. Check for continuity in fuel pump relay circuit between PCM and fuel pump relay. If circuit is open, repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If circuit is okay, go to next step.
7. Check fuel pump relay circuit for poor terminal connection at PCM. Replace as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If terminal connection is okay, go to step 20).
8. Check for poor terminal connection at fuel pump relay. Repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If connection is okay, go to step 18).
9. Using test light connected to ground, probe battery feed circuit (Red wire) at fuel pump relay harness connector. If test light illuminates, go to step 17). If test light does not illuminate, go to step 16).
10. Remove fuel filler cap and listen for fuel pump operation. If fuel pump is operating, diagnose fuel system. See «BASIC FUEL SYSTEM CHECKS»(ref-20674-S29918334612001010200000) . If fuel pump is not operating, go to next step.
11. Raise vehicle (leave fuel pump circuit jumpered). Disconnect fuel pump harness connector. Connect a test light between fuel pump harness connector terminals. If test light illuminates, go to step 19). If test light does not illuminate, go to next step.
12. Connect test light to chassis ground. Probe fuel pump harness connector terminal (Gray wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 14).
13. Locate and repair open in fuel pump ground circuit (Black wire). After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
14. Locate and repair open in fuel pump feed circuit (Gray wire). After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
15. Locate and repair short to ground in fuel pump relay PCM feed circuit (Dark Green/White wire). After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
16. Locate and repair open in ignition feed to fuel pump relay circuit (Red wire). After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
17. Locate and repair open in ground circuit to fuel pump relay (Black/White wire). After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
18. Replace fuel pump relay. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
19. Replace fuel pump. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
20. Replace PCM. Perform PCM relearn procedures. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .

FUEL SYSTEM PRESSURE RELIEF

Fuel system is under pressure, which must be relieved before servicing fuel system.

Fuel pressure may be relieved by the following method

1. Disconnect negative battery cable. Loosen fuel filler cap. Install Fuel Pressure Gauge (J-34730-1A) to fuel pressure test head. Wrap shop towel around pressure connection when installing fuel pressure gauge to absorb fuel leakage. Place gauge bleed hose in container. Open bleed valve to relieve fuel pressure.

BASIC IGNITION SYSTEM CHECKS

Note. To diagnose ignition system, see appropriate IGNITION SYSTEM test in NO-START DIAGNOSIS .

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specifications. For specifications, see SPECIFICATIONS article. For adjustment procedures, see ADJUSTMENTS article.

The OBD System Check determines

1. If Malfunction Indicator Light (MIL) works.
2. If PCM/VCM is operating and can recognize a fault.
3. If any Diagnostic Trouble Codes (DTCs) are stored.

After performing procedures in PRELIMINARY INSPECTION & ADJUSTMENTS, BASIC FUEL SYSTEM CHECKS and BASIC IGNITION SYSTEM CHECKS, this is the starting point for utilizing the self-diagnostic system for determining computer-related problems. After performing necessary tests as described in the OBD system circuit check, if no codes are indicated and driveability problems still exist, see testing procedures in the TESTS W/O CODES article and SCAN TOOL usage in the TESTS W/CODES article.

1. Turn ignition on with engine off. Observe Malfunction Indicator Light (MIL). If MIL illuminates, go to next step. If MIL does not illuminate, go to «MALFUNCTION INDICATOR LIGHT (MIL)»(ref-20674-S31197973732001010200000) .
2. Turn ignition off. Install Tech 1 scan tool and follow scan tool manufacturer's instructions to proceed with test. Turn ignition on. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to «DLC DIAGNOSIS OR NO SCAN TOOL DATA»(ref-20674-S05366098422001010200000) .
3. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start, or starts and dies, go to «NO-START DIAGNOSIS»(ref-20674-S15836842092001010200000) .
4. Using scan tool, observe DTC status LAST TST FAIL function. If any DTC is stored, save freeze frame and fail record information using CAPTURE INFO feature. If a DTC is indicated as last test failed, diagnose affected DTC. See the «TESTS W/CODES»(ref-20678) article. If DTC is not indicated, go to next step.
5. Using scan tool, display DTC fail records. If a DTC fail record is stored, save freeze frame and fail record information using scan tool CAPTURE INFO feature. If a fail record is stored, diagnose affected DTC. See the «TESTS W/CODES»(ref-20678) article. If DTC is not indicated, go to next step.
6. Compare scan tool engine data with actual control system data values. If value is within limits, system is okay. If value is not within limits, go to the «SYSTEM/COMPONENT TESTS»(ref-20675) article.

MALFUNCTION INDICATOR LIGHT (MIL)

1. Perform On-Board Diagnostic (OBD) System Check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . After performing OBD system check, go to next step.
2. Attempt to start engine. If engine starts, go to next step. If engine does not start, go to step 6).
3. Check instrument cluster ignition feed circuit fuse. See the «WIRING DIAGRAMS»(ref-20677) article. If fuse is okay, go to next step. If fuse is faulty, go to step 15).
4. Turn ignition on. Using test light connected to ground, probe ignition feed circuit at cluster connector. See the «WIRING DIAGRAMS»(ref-20677) article. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
5. Turn ignition off. Disconnect PCM harness connector. Turn ignition on. Using a fused jumper wire, connect MIL driver circuit at PCM to ground. See the «WIRING DIAGRAMS»(ref-20677) article. If MIL illuminates, go to step 10). If MIL does not illuminate, go to step 11).
6. Check PCM ignition feed and battery feed fuses. If both fuses are okay, go to step 7). If fuse(s) are faulty, go to step 14).
7. Turn ignition off. Disconnect PCM harness connector. Using a test light connected to ground, probe ignition feed circuit at PCM harness connector terminal. See the «WIRING DIAGRAMS»(ref-20677) article. If test light illuminates, go to next step. If test light does not illuminate, go to step 13).
8. With test light connected to ground, probe battery feed circuit at PCM harness connector terminal. See the «WIRING DIAGRAMS»(ref-20677) article. If test light illuminates, go to next step. If test light does not illuminate, go to step 13).
9. Check for faulty PCM or poor PCM ground connection. Repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If circuit is okay, go to next step.
10. Check for poor PCM connection. Repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If PCM connection is okay, go to step 16).
11. Check for open in MIL driver circuit. Repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If circuit is okay, go to step 17).
12. Repair open in ignition feed circuit to instrument cluster indicators. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
13. Locate and repair open in PCM battery feed circuit or PCM ignition feed circuit. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
14. Locate and repair short to ground in PCM ignition feed circuit or PCM battery feed circuit. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
15. Locate and repair short to ground in feed circuit to instrument cluster indicators. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
16. Replace PCM. Perform PCM relearn procedures. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) .
17. Check for poor connection at MIL driver circuit in instrument cluster connector. Repair as necessary. After repairs, perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20674-S33370786602001010200000) . If MIL driver circuit connections are okay, diagnose instrument panel. See the INSTRUMENT PANEL article in the ACCESSORIES/SAFETY EQUIPMENT section.

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, no trouble codes (or only intermittent ones) were found while performing ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK and driveability problems exist, proceed to the TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.