Engine Controls - Basic Diagnostic Procedures - 3.1l Chevrolet Malibu V

INTRODUCTION

The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for a no-start condition.

The first step in diagnosing any driveability problem is verifying the customer's complaint with a test drive under the conditions during which the problem reportedly occurred.

Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.

Note. Unless otherwise instructed in test procedures, perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance.

VISUAL INSPECTION

Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and not pinched or cut. If necessary, see VACUUM DIAGRAMS - 3.1L article to verify routing and connections. Inspect air induction system for possible vacuum leaks.

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 SPECIFICATIONS - 3.1L 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.

Diagnosis

1. Start engine and bring to operating temperature. Increase engine speed to 2000-2500 RPM and note gauge. If reading exceeds 1.25 psi (.09 kg/cm 2 ), exhaust system is restricted.
2. Check exhaust system for collapsed pipe, heat distress and possible internal muffler failure. If none of these conditions exist, check for restricted catalytic converter. Replace as required.

NO START DIAGNOSIS

Note. Some vehicles are equipped with anti-theft systems (VATS or PASS-Key(R)) which will not allow vehicle to be started if improper starting procedures or improperly coded ignition keys are used. Both fuel injection and cranking systems will be disabled. Loss of fuel enable signal from anti-theft decoder module should set a diagnostic trouble code in PCM memory.

Note. For terminal and circuit identification, see WIRING DIAGRAMS - 3.1L article.

Definition

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

NO START - ENGINE CRANKS OKAY (WITH DIS)

Note. Before performing following tests, check battery condition, engine cranking speed and for adequate fuel in tank.

General Inspection

1. Ensure proper starting procedure is being used. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at both coil pack and spark plugs.
2. Remove spark plugs. Check and replace as necessary. In very cold temperatures, ensure oil is proper viscosity and not contaminated with gasoline.

Ignition System

1. Perform On-Board Diagnostic (OBD) System Check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select FAILED SINCE CODE CLEAR function. If Diagnostic Trouble Code (DTC) P0101, P0123, P0601/P0602, P0201-206, P1374 or P1629 is present, diagnose DTC(s). See TESTS W/CODES - 3.1L article. If DTC(s) is 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 greater 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»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l__basic-fuel-system-checks) . If fuel pressure is not present, go to FUEL SYSTEM ELECTRICAL CIRCUIT.
7. Turn ignition off. Disconnect 10-pin fuel injector/engine 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 cylinders 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 a short to ground in injector feed circuit, or shorted injector. Repair as necessary. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article. If circuit and injector are okay, go to next step.
10. Check for open in fuel injector feed circuit. Repair as necessary. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article. If circuit is okay, go to step 31).
11. Check fuse to Ignition Control Module (ICM) ignition feed circuit. If fuse is faulty, check for short to ground in ICM feed circuit or short to voltage in IC control circuit. Repair as necessary. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article. 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 in TESTS W/CODES - 3.1L article. If circuits are okay, go to next step.
13. Disconnect 7X Crankshaft Position (CKP) sensor connector from ICM. Connect DVOM between CKP sensor 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 in TESTS W/CODES - 3.1L article. 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 in TESTS W/CODES - 3.1L article. 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 in TESTS W/CODES - 3.1L article. If coil(s) are okay, go to next step.
17. Check secondary resistance of 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 in TESTS W/CODES - 3.1L article. 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 in TESTS W/CODES - 3.1L article. 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 in TESTS W/CODES - 3.1L article. 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 in TESTS W/CODES - 3.1L article. 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 in TESTS W/CODES - 3.1L article. 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 in TESTS W/CODES - 3.1L article. If fuel is not contaminated, check for poor or damaged PCM connector, for faulty engine coolant temperature sensor, or mass airflow miscalculated due to faulty TP sensor or MAP sensor. See SYSTEM/COMPONENT TESTS - 3.1L 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 in TESTS W/CODES - 3.1L article.
27. Replace MAP sensor. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.
28. Replace 7X CKP sensor. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.
29. Replace ignition coil(s) associated with cylinder that did not produce a spark. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.
30. Replace ICM. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.
31. Replace PCM. Perform PCM relearn procedures. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.

Fuel System Electrical Circuit

1. Perform On-Board Diagnostic (OBD) System Check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article. After performing OBD system check, go to next step.
2. Turn ignition off. Install fuel pressure gauge. Remove fuel pump relay. Using a fused jumper wire, jumper fuel pump feed circuit at fuel pump relay connector to battery voltage. See WIRING DIAGRAMS - 3.1L article. 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 from fuel pump relay connector. Connect test light between fuel pump relay connector terminals for ignition feed circuit and ground circuit. See WIRING DIAGRAMS - 3.1L article. Turn ignition on. If test light illuminates, go to next step. If test light does not illuminate, go to step 9).
4. Turn ignition off. Connect test light between fuel pump relay connector terminals for fuel pump relay driver circuit and ground circuit. See WIRING DIAGRAMS - 3.1L article. Turn ignition on. Test light should illuminate for about 2 seconds. If test light illuminates, go to step 8). If test light does not illuminate, go to next step.
5. Turn ignition off. Disconnect PCM connector. Using a test light connected to battery voltage, probe fuel pump driver circuit at PCM connector. If test light illuminates, go to step 15). If test light does not illuminate, go to next step.
6. Check continuity of fuel pump relay driver circuit between PCM and fuel pump relay. See WIRING DIAGRAMS - 3.1L article. If circuit is open, repair as necessary. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article. If circuit is okay, go to next step.
7. Check fuel pump relay driver circuit for poor terminal connection at PCM. If connection is faulty, repair as necessary. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article. If connection is okay, go to step 20).
8. Check for poor fuel pump relay terminal connection. If connection is faulty, repair as necessary. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article. If connection is okay, go to step 18).
9. Using a test light connected to ground, probe ignition feed circuit at fuel pump relay connection. See WIRING DIAGRAMS - 3.1L article. 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 running, diagnose fuel system. See «BASIC FUEL SYSTEM CHECKS»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l__basic-fuel-system-checks) . If fuel pump is not running, go to next step.
11. Using a fused jumper wire connected to battery voltage, jumper fuel pump feed circuit. See WIRING DIAGRAMS - 3.1L article. Raise and support vehicle. Disconnect fuel sending unit connector at fuel tank. Using a test light, check circuit between fuel sending unit connector. If test light illuminates, go to step 19). If test light does not illuminate, go to next step.
12. Using a test light connected to ground, probe fuel pump feed circuit at fuel sending unit connector. See WIRING DIAGRAMS - 3.1L article. If test light does not illuminate, go to next step. If test light illuminates, go to step 14).
13. Locate and repair open in fuel pump feed circuit. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.
14. Locate and repair open in fuel pump ground circuit. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.
15. Locate and repair short to ground in fuel pump relay driver circuit. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.
16. Locate and repair open in ignition feed circuit to fuel pump relay. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.
17. Locate and repair open in ground circuit to fuel pump relay. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.
18. Replace fuel pump relay. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.
19. Replace fuel pump. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.
20. Replace PCM. Perform PCM relearn procedures. After repairs, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article.

BASIC FUEL SYSTEM CHECKS

Note. For fuel pump circuit testing, see FUEL SYSTEM ELECTRICAL CIRCUIT under NO START DIAGNOSIS .

FUEL SYSTEM PRESSURE RELIEF

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

1. Disconnect negative battery terminal. Loosen fuel filler cap. Install Fuel Pressure Gauge (J-34730-1A) 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 SYSTEM PRESSURE TEST

1. Perform On-Board Diagnostic (OBD) System Check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES - 3.1L article. After performing OBD system check, go to next step.
2. Turn ignition off. Turn A/C system off. Connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure fitting on fuel rail. Place fuel pressure gauge bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should run for about 2 seconds. Cycle ignition to obtain highest fuel pressure possible. Observe fuel pressure with fuel pump running. Fuel pressure should be within specification. See «FUEL PRESSURE»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l) table. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, go to step 12).
3. Fuel pressure may vary slightly when fuel pump stops. After fuel pump stops, fuel pressure should stabilize and remain constant. Note fuel pressure when fuel pump stops running. If fuel pressure decreases more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, go to step 10). If fuel pressure does not decrease more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, go to next step.
4. Relieve fuel pressure until pressure is 10 psi (0.7 kg/cm 2 ). If fuel pressure decreases more than 2 psi (0.1 kg/cm 2 ) in 10 minutes, go to step 19). If fuel pressure does not decrease more than 2 psi (0.1 kg/cm 2 ) in 10 minutes, go to next step.
5. If fuel pressure is suspected of decreasing during acceleration, cruise or hard cornering, go to next step. If fuel pressure is not suspected of decreasing during acceleration, cruise or hard corning, go to step 8).
6. Inspect in-line fuel filter and fuel feed pipe for restriction. If restriction is found, go to step 24). If restriction is not found, go to next step.
7. Remove fuel sending unit assembly. Inspect fuel pump strainer for restriction, fuel pump strainer for proper positioning and installation on fuel sending unit assembly, fuel pump flex pipe for leaks, and ensure fuel pump is proper pump for vehicle. If a problem is found, go to step 24). If a problem is not found, go to step 19).
8. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should run for about 2 seconds. Cycle ignition to obtain highest fuel pressure possible. Note fuel pressure. Start engine. Allow engine to idle until normal operating temperature is reached. If fuel pressure is less than previously noted pressure by 3-10 psi (0.2-0.7 kg/cm 2 ), see TESTS W/O CODES - 3.1L article. If fuel pressure is greater than previously noted pressure by 3-10 psi (0.2-0.7 kg/cm 2 ), go to next step.
9. Disconnect vacuum hose from fuel pressure regulator. With engine idling, apply 12-14" of vacuum to fuel pressure regulator. If fuel pressure decreases by 3-10 psi (0.2-0.7 kg/cm 2 ), go to step 20). If fuel pressure does not decrease by 3-10 psi (0.2-0.7 kg/cm 2 ), go to step 21).
10. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l__fuel-system-pressure-relief) . Place bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Using scan tool, pressurize fuel system. DO NOT allow fuel pressure to exceed 65 psi (4.5 kg/cm 2 ). Excess pressure may damage fuel pressure regulator. Wait for fuel pressure to build. Using scan tool, obtain highest fuel pressure possible. Gradually pinch off fuel feed hose. If fuel pressure remains constant, go to step 19). If fuel pressure does not remain constant, go to next step.
11. Gradually unpinch fuel feed hose. Using scan tool, pressurize fuel system. Wait for fuel pressure to build. Gradually pinch off fuel return hose. If fuel pressure remains constant, go to step 21). If fuel pressure does not remain constant, go to step 22).
12. If fuel pressure is greater than specification, go to next step. See «FUEL PRESSURE»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l) table. If fuel pressure is less than specification, go to step 15).
13. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l__fuel-system-pressure-relief) . Disconnect fuel return pipe from fuel rail. Attach a flexible fuel hose to fuel rail return outlet passage. Place other end of flexible hose into container. Turn ignition off for about 10 seconds. Turn ignition on. Observe fuel pressure gauge with fuel pump running. Fuel pressure should be within specification. See «FUEL PRESSURE»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l) table. If fuel pressure is within specification, go to step 23). If fuel pressure is not within specification, go to next step.
14. Inspect fuel rail outlet passage for restriction. If restriction is found, go to step 24). If restriction is not found, go to step 21).
15. If fuel pressure is greater than zero psi, go to next step. If fuel pressure is zero psi, go to step 17).
16. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELIEF»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l__fuel-system-pressure-relief) . Place bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Using scan tool, pressurize fuel system. DO NOT allow fuel pressure to exceed 65 psi (4.5 kg/cm 2 ). Excess pressure may damage fuel pressure regulator. Wait for fuel pressure to build. Using scan tool, obtain highest fuel pressure possible. Gradually pinch off fuel return hose. If fuel pressure increases to greater than specification, go to step 21). See «FUEL PRESSURE»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l) table. If fuel pressure does not increase to greater than specification, go to step 7).
17. Check fuel pump electrical circuit. See FUEL SYSTEM ELECTRICAL CIRCUIT under «NO START DIAGNOSIS»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l__no-start-diagnosis) . If a problem is found in electrical circuit, go to step 24). If electrical circuit is okay, go to next step.
18. Remove fuel sending unit assembly. Inspect in-line fuel filter for obstructions, fuel feed pipe for a restriction, fuel pump strainer for obstructions, and fuel pump flex pipe for leaks. If a problem is found, go to step 24). If a problem is not found, go to next step.
19. Replace fuel sending unit assembly. After replacing fuel sending unit assembly, go to step 25).
20. Locate and repair loss of vacuum to fuel pressure regulator. After repairing vacuum loss, go to step 25).
21. Replace fuel pressure regulator. After replacing fuel pressure regulator, go to step 25).
22. Locate and replace leaking fuel injector(s). After replacing fuel injector(s), go to step 25).
23. Locate and repair restriction in fuel return pipe. After repairing restriction, go to step 25).
24. Repair problem as necessary. After repairing problem, go to step 25).
25. Turn ignition off. Turn A/C system off. Connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure fitting on fuel rail. Place fuel pressure gauge bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should run for about 2 seconds. Cycle ignition to obtain highest fuel pressure possible. Observe fuel pressure with fuel pump running. Fuel pressure should be within specification. See «FUEL PRESSURE»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l) table. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, go to step 11).
26. Fuel pressure may vary slightly when fuel pump stops. After fuel pump stops, fuel pressure should stabilize and remain constant. Note fuel pressure when fuel pump stops running. If fuel pressure decreases more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, go to step 10). If fuel pressure does not decrease more than 5 psi (0.3 kg/cm 2 ) in 10 minutes, system is okay.

FUEL PRESSURE

Spark

1. If factory tachometer is connected to coil tachometer terminal, disconnect tachometer before performing tests. When removing spark plug wire from spark plug, twist and pull on boot. DO NOT pull on wire.
2. Using Spark Tester (J-26792), check for spark at each spark plug wire. Leave other wires connected while checking for spark. Check spark plug wire resistance on suspect wires. Resistance should be about 30,000 ohms.

Ignition Coil Power Source

Turn ignition on. Check ignition positive voltage circuit of ignition control module for battery voltage. See WIRING DIAGRAMS - 3.1L article. If battery voltage is not present, check ignition or PCM fuse. If fuse is not blown, check for open between fuse and ignition control module.

Ignition Coil Resistance

If ignition coil is suspected of causing misfire or no-spark condition, switch coil locations on ignition control module. If problem follows questionable coil, check ignition coil resistance or replace original coil. For ignition coil resistance, see IGNITION COIL RESISTANCE table.

IGNITION COIL RESISTANCE

Crankshaft Position (CKP) Sensor Pick-Up Coil Short & Resistance Checks

1. Set DVOM on 2000-ohm scale. Connect DVOM leads to CKP sensor connector located on side of engine block. Turn ignition off. Disconnect ignition control module connectors. Check resistance between CKP sensor terminals at ignition control module connector.
2. CKP sensor resistance should be within specification range. See «CRANKSHAFT POSITION (CKP) SENSOR RESISTANCE»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-31l) table. If resistance is not within specification, replace CKP sensor. If sensor is within specification, go to next step.
3. With CKP sensor installed in block, connect one ohmmeter lead to either sensor terminal at ignition control module. Touch other lead of ohmmeter to engine block. No continuity should exist. If continuity exists, CKP sensor is shorted to ground and must be repaired or replaced.

CRANKSHAFT POSITION (CKP) SENSOR RESISTANCE (1)

Crankshaft Position (CKP) Sensor Output Signal

Set DVOM on 2-volt AC scale. Connect DVOM leads to CKP sensor located on side of engine block. Crank engine and observe voltmeter reading. CKP sensor should generate a voltage signal of about 2 volts.

Tach Pulse (RPM) Signal

Connect scan tool to DLC. RPM should be indicated on scan tool when engine is cranked or running. Tach pulse (RPM reference) will be indicated as a voltage signal when a DVOM (with a minimum 10-megohm input impedance connected to ground) is used to backprobe RPM high reference circuit. If tach pulse signal is not present, vehicle will not run. For circuit and terminal identification, see WIRING DIAGRAMS - 3.1L article.

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. For specifications, see SPECIFICATIONS - 3.1L article. For adjustment procedures, see ADJUSTMENTS - 3.1L 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 appropriate TESTS W/O CODES - 3.1L article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.

See also:
• G - TESTS W/CODES - 3.1L
• BASIC FUEL SYSTEM CHECKS
• NO START DIAGNOSIS
• FUEL PRESSURE
• FUEL SYSTEM PRESSURE RELIEF