Engine Control System - Basic Engine Testing - 5.7L: Other Pontiac Firebird IV

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 one of the following manners

1. Check At AIR Check Valve Remove AIR check valve. Install backpressure tester in place of AIR check valve.
2. 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 properly, but does not start. Engine may fire a few times.

Ignition System

1. Perform On-Board Diagnostic (OBD) System Check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20656-S10587673782001010200000) . After performing OBD system check, go to next step.
2. Install scan tool. Using scan tool, select ENG DTC, DTC INFO, LAST TST FAIL function. If Diagnostic Trouble Code (DTC) P0100, P0200, P0601, P0602, P1351, P1361 or P1371 is present, diagnose DTC(s) first. See the TESTS W/CODES article. If DTC(s) is not present, go to next step.
3. Using scan tool, check PASS-Key(R) status. If PASS-Key(R) status is not okay, check theft deterrent system. See the ANTI-THEFT SYSTEM article in the ACCESSORIES/SAFETY EQUIPMENT section. If PASS-Key(R) status is okay, go to next step.
4. Using scan tool, check engine coolant temperature. Engine coolant temperature reading on scan tool should be close to actual engine temperature. If coolant temperature reading is as specified, go to next step. If scanned coolant temperature is not close to actual engine temperature reading, diagnose problem using DTC P0118. See the TESTS W/CODES article.
5. Using scan tool, check throttle angle. Throttle angle should be zero percent at closed throttle. If throttle angle is as specified, go to next step. If throttle angle is not as specified, diagnose problem using DTC P0122. See the TESTS W/CODES article.
6. Using scan tool, check engine speed while cranking engine. If RPM is indicated on scan tool, go to next step. If RPM is not indicated on scan tool, go to step 11).
7. Using Spark Tester (J-26792), check spark on any 2 wires while cranking engine. If spark is present, go to next step. If spark is not present, check ignition system. See «BASIC IGNITION SYSTEM CHECKS»(ref-20656-S42609786712001010200000) .
8. Using scan tool, enable fuel pump. If fuel pump operates, go to next step. If fuel pump does not operate, go to FUEL SYSTEM.
9. Turn ignition off. Install fuel pressure gauge. Turn ignition on and observe fuel pressure gauge reading. 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, diagnose fuel system. See «BASIC FUEL SYSTEM CHECKS»(ref-20656-S28756266282001010200000) .
10. Check for sticking EGR valve. Check for leak in air duct between Mass Airflow (MAF) sensor and throttle body. Check for faulty MAF sensor. To check MAF sensor, unplug MAF sensor then attempt to start engine. If engine starts and idles, MAF sensor is faulty. After repairs, go to step 21). If EGR, air duct and MAF sensor are okay, see the TESTS W/O CODES article.
11. Turn ignition off. Disconnect distributor connector. Turn ignition on. Using a test light connected to ground, probe distributor connector ignition feed circuit. See the WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 13).
12. Using DVOM, check resistance between distributor connector reference low circuit and ground. See the WIRING DIAGRAMS article. Resistance should be 5 ohms or less. If resistance is as specified, go to step 21). If resistance is not as specified, go to step 15).
13. Turn ignition off. Disconnect PCM connector C2. Using DVOM, check resistance of ignition feed circuit between distributor connector and PCM connector. See the WIRING DIAGRAMS article. Resistance should be 5 ohms or less. If resistance is as specified, go to next step. If resistance is not as specified, go to step 16).
14. Using DVOM, check resistance between distributor connector ignition feed circuit and ground. Resistance should be infinite. If resistance is as specified, go to step 20). If resistance is not as specified, go to step 17).
15. Turn ignition off. Disconnect PCM connector C2. Using DVOM, check resistance of reference low circuit between distributor connector and PCM connector. See the WIRING DIAGRAMS article. Resistance should be 5 ohms or less. If resistance is as specified, go to step 20). If resistance is not as specified, go to step 18).
16. Repair open in ignition feed circuit to distributor. After repairs, go to step 22).
17. Repair short to ground in ignition feed circuit to distributor. After repairs, go to step 22).
18. Repair distributor reference low circuit. After repairs, go to step 22).
19. Replace distributor assembly. After distributor replacement, go to step 22).
20. Check PCM connections. Repair as necessary. After repairs, go to step 22). If connections are okay, go to next step.
21. Replace PCM. Perform PCM relearn procedures. After repairs, go to next step.
22. Using scan tool, clear DTC(s). Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and then dies, go to step 2).
23. Warm engine to normal operating temperature. Using scan tool, select DTC, FAILED THIS IGN function. If any DTC(s) is present, diagnose DTC(s). See the TESTS W/CODES article. If DTC(s) is not present, go to next step.
24. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any DTC(s) is present, diagnose DTC(s). See the TESTS W/CODES article. If DTC(s) are not present, system is okay.

Fuel System

1. Perform On-Board Diagnostic (OBD) System Check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-20656-S10587673782001010200000) . After performing OBD system check, go to next step.
2. Check fuel pump fuse. If fuse is okay, go to next step. If fuse is open, go to step 9).
3. Remove fuel pump relay. Using a test light connected to ground, probe fuel pump relay battery feed circuit. See the WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
4. Using a test light connected to battery voltage, probe fuel pump relay connector ground circuit. See the WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 13).
5. Using a test light connected to ground, probe fuel pump relay connector control circuit. See the WIRING DIAGRAMS article. Using scan tool, command fuel pump on. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
6. Using a fused jumper wire, jumper fuel pump connector battery feed circuit to fuel pump circuit. See the WIRING DIAGRAMS article. Fuel pump should operate. If fuel pump operates, go to step 18). If fuel pump does not operate, go to next step.
7. Leave jumper wire connected. Disconnect fuel pump connector. Using a test light connected to ground, probe fuel pump connector power feed circuit. See the WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 14).
8. Leave jumper wire connected. Connect test light between fuel pump connector power feed circuit and ground circuit. If test light illuminates, go to step 20). If test light does not illuminate, go to step 15).
9. Turn ignition off. Remove fuel pump fuse. Disconnect fuel pump connector. Using a test light connected to battery voltage, probe fuel pump connector power feed circuit. If test light illuminates, go to step 16). If test light does not illuminate, go to next step.
10. Reconnect fuel pump connector. Install NEW fuel pump fuse. Turn ignition on. Recheck fuel pump fuse. If fuse blows, go to step 20). If fuse is okay, check for intermittent short in fuel pump power feed circuit or an intermittent internal fuel pump problem.
11. Turn ignition off. Disconnect PCM connector C1. Using DVOM, check resistance of fuel pump relay control circuit between fuel pump relay connector and PCM connector. Resistance should be 5 ohms or less. If resistance is as specified, go to step 22). If resistance is not as specified, go to step 17).
12. Repair open in fuel pump relay battery feed circuit. After repairs, go to step 24).
13. Repair open in fuel pump relay ground circuit. After repairs, go to step 24).
14. Repair open in fuel pump feed circuit. After repairs, go to step 24).
15. Repair open in fuel pump ground circuit. After repairs, go to step 24).
16. Repair short to ground in fuel pump feed circuit. After repairs, go to step 24).
17. Repair fuel pump relay control circuit. After repairs, go to step 24).
18. Check for poor fuel pump relay connections. After repairs, go to step 24). If connections are okay, go to next step.
19. Replace fuel pump relay. After repairs, go to step 24).
20. Check fuel pump harness for damage. After repairs, go to step 24). If harness is okay, go to next step.
21. Replace fuel pump. After repairs, go to step 24).
22. Check for poor PCM connections. Repair as necessary. After repairs, go to step 24). If connections are okay, go to next step.
23. Replace PCM. Perform PCM relearn procedures. After repairs, go to next step.
24. Using scan tool, clear DTC(s). Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and dies, go to step 2).
25. Warm engine to normal operating temperature. Using scan tool, select DTC, FAILED THIS IGN function. If any DTC(s) is present, diagnose DTC(s). See the TESTS W/CODES article. If DTC(s) is not present, go to next step.
26. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any DTC(s) is present, diagnose DTC(s). See the TESTS W/CODES article. If DTC(s) are not present, system is okay.

BASIC FUEL SYSTEM CHECKS

Fuel Pressure Relief

Fuel system is under pressure. Pressure must be relieved prior to servicing fuel system. Fuel pressure may be relieved by using one of the following methods

1. Disconnect negative battery terminal. Loosen fuel filler cap. Install Fuel Pressure Gauge (J-34730-1) on fuel pressure connector of fuel rail. Wrap shop towel around pressure connection when installing fuel pressure gauge to absorb fuel leakage. Install gauge bleed hose in container. Open bleed valve to bleed fuel pressure.

Fuel Pressure Check

1. Relieve fuel pressure. See FUEL PRESSURE RELIEF. Connect Fuel Pressure Gauge (J-34730-1) to fuel pressure fitting on fuel rail. Turn ignition on with engine off. Fuel pressure should be within specification. See «FUEL PRESSURE»(ref-20656-S05401467632001010200000) table. If no fuel pressure is present, go to step 5).
2. Start engine. Fuel pressure should drop 3-10 psi (.2-.7 kg/cm 2 ). Turn ignition off. Pressure should hold. If fuel pressure does not hold, check for leaking injectors or fittings. If injectors or fittings are not leaking, replace fuel pressure regulator.
3. If fuel pressure is less than specified, check for restricted fuel line or fuel filter. Repair as necessary. If no restriction is evident, apply battery voltage to fuel pump test connector using a 10-amp fused jumper wire. For location of fuel pump test connector, see COMPONENT LOCATIONS in the SYSTEM/COMPONENT TESTS article.
4. Gradually pinch off fuel return line between gauge and fuel tank. If fuel pressure increases to within specification, replace fuel pressure regulator. If fuel pressure does not increase with line pinched, check for faulty in-tank fuel pump or partially blocked fuel strainer.
5. Using a 10-amp fused jumper wire, apply battery voltage to fuel pump test connector. For location of fuel pump test connector, see COMPONENT LOCATIONS in the SYSTEM/COMPONENT TESTS article. Observe fuel pressure reading. If fuel pressure is still not present, check wiring between test connector and fuel pump. If wiring is okay, replace fuel pump.
6. If fuel pressure is present with voltage applied to test connector, test fuel pump relay and voltage supply to relay. See the SYSTEM/COMPONENT TESTS article.

FUEL PRESSURE

Fuel Pump Relay

See MOTORS, RELAYS & SOLENOIDS in the SYSTEM/COMPONENT TESTS article.

Fuel Pump Relay By-Pass Procedure

See FUEL DELIVERY in the SYSTEM/COMPONENT TESTS article.

Spark

Disconnect tachometer wire (if equipped). A shorted tachometer will prevent vehicle from starting. Using Spark Tester (J-26792), check for adequate spark. Check for spark on more than one plug wire. When removing spark plug wire from spark plug, twist and pull on boot. DO NOT pull on wire.

Ignition Coil Power Source

Turn ignition on. Check for battery voltage on ignition feed circuit to ignition coil. If battery voltage is not present, check for blown 10-amp COIL fuse. If fuse is okay, check for open between fuse and ignition coil.

Ignition Coil Resistance

Information not available at time of publication.

Tach Pulse (RPM Reference) Signal

Connect scan tool to DLC. Scan low and high resolution reference pulses. Both high and low pulses should be present when engine is cranking or running. If low resolution pulse is not present, engine will not start and PCM will set a Diagnostic Trouble Code (DTC) in memory. If high resolution pulse is not present, vehicle will still run; however, PCM will set a DTC in memory. For circuit and terminal identification, See the WIRING DIAGRAMS article.

IDLE SPEED & IGNITION TIMING

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

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 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.