Engine Controls - System Testing & Engine Component Tests - 3.1l Chevrolet Malibu V

MODEL IDENTIFICATION

Vehicle model is identified by fourth character of Vehicle Identification Number (VIN). VIN is stamped on metal pad on top of left end of instrument panel, near windshield.

INTRODUCTION

Before testing separate components or systems, perform all procedures listed in BASIC TESTING - 3.1L article. Since many computer-controlled and monitored components will set a diagnostic trouble code if they malfunction, it is also recommended self-diagnosis be performed. See TESTS W/CODES - 3.1L article.

Note. Testing individual components does not isolate shorts or opens. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.

Ground Circuits

1. Using an ohmmeter, check for continuity to ground at PCM ground terminals. See «POWERTRAIN CONTROL MODULE (PCM) CONNECTOR I.D.»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-system-testing-engine-component-tests-31l) table. Resistance should be zero ohms. If not, repair open to ground.
2. Using a voltmeter, connect negative lead of voltmeter to a good ground. Backprobe positive lead of voltmeter to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is more than one volt, check for open, short to voltage, corrosion or loose connection on ground circuit.

Power Circuits

1. Using a voltmeter, check for battery voltage between PCM continuous power terminal(s) and ground. See «POWERTRAIN CONTROL MODULE (PCM) CONNECTOR I.D.»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-system-testing-engine-component-tests-31l) table. If battery voltage is not present, check for blown fuse or open fusible link. If okay, check for open in wire between PCM terminal and power source.
2. Turn ignition switch to RUN position. Using a voltmeter, check for battery voltage between PCM ignition power terminals and ground. If battery voltage is not present, check IGN fuse. If fuse is okay, check for an open in wire between battery and ignition switch, and between ignition switch and PCM terminal. If okay, check for a defective ignition switch.
3. Connect voltmeter between ground and PCM starter (crank) signal terminal. On vehicles with manual transmission/transaxle, depress clutch pedal. On vehicles with automatic transmission/transaxle, position gear shift lever in Park. On all vehicles, turn ignition switch to START position. Battery voltage should be present only when ignition switch is in START position.
4. If voltage is not present, check CRANK fuse or fusible link between ignition switch and PCM terminal. If fuse or fusible link is okay, check for an open in wire between ignition switch and PCM terminal, or check for a defective ignition switch.

PCM Harness Resistance

Turn ignition switch to LOCK position. Disconnect PCM and appropriate component harness connectors. Check for open or short circuits between PCM harness connector terminal and component harness connector terminal. See POWERTRAIN CONTROL MODULE (PCM) CONNECTOR I.D. table. See WIRING DIAGRAMS - 3.1L article. If harness is open or shorted, repair as necessary.

Scheme 4

POWERTRAIN CONTROL MODULE (PCM) CONNECTOR I.D. (1)

TROUBLE CODE DEFINITIONS

TROUBLE CODE DEFINITION

ENGINE SENSORS & SWITCHES

Note. For additional sensor testing specifications, see SENSOR RANGE CHARTS - 3.1L article.

Manufacturer does not provide many individual system and component testing. For sensor and switch testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES - 3.1L article.

Engine Oil Level Sensor Diagnosis

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
2. Using scan tool, observe engine oil level display. If scan tool does not display OK, go to next step. If scan tool displays OK, check for poor connections at sensor and PCM. If poor connection exists, repair as necessary. If poor connection does not exist, perform warning light diagnosis. See «PCM CONTROLLED WARNING LIGHTS»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-system-testing-engine-component-tests-31l) under MISCELLANEOUS CONTROLS.
3. Turn ignition switch to LOCK position. Disconnect PCM harness connectors. Using a test light connected to battery voltage, probe engine oil level sensor signal circuit (Brown wire) at PCM harness connector. If test light does not illuminate, go to next step. If test light illuminates, go to step 7).
4. Ensure ignition switch is in LOCK position. Connect PCM harness connectors. Turn ignition switch to RUN position. Raise and support vehicle. Disconnect engine oil level sensor harness connector. Measure voltage between engine oil level sensor harness connector terminals. If battery voltage does not exist, go to next step. If battery voltage exists, go to step 8).
5. Measure voltage at engine oil level signal circuit (Brown wire) at engine oil level sensor harness connector. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 9).
6. Check engine oil level sensor signal circuit (Brown wire) for open, between PCM and engine oil level sensor harness connectors. If open exists, repair as necessary and go to step 12). If open does not exist, check for poor connections at sensor and PCM. If poor connection exists, repair as necessary. If poor connection does not exist, perform warning light diagnosis. See «PCM CONTROLLED WARNING LIGHTS»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-system-testing-engine-component-tests-31l) under MISCELLANEOUS CONTROLS.
7. Check for poor connections at PCM. If poor connection exists, repair as necessary and go to step 12). If poor connection does not exist, go to step 11).
8. Check for poor connections at engine oil level sensor. If poor connection exists, repair as necessary and go to step 12). If poor connection does not exist, go to step 10).
9. Locate and repair open in engine oil level sensor ground circuit (Black/White wire). After repair are complete, go to step 12).
10. Replace engine oil level sensor and go to step 12).
11. Replace PCM and go to next step.
12. Start engine and allow to warm to normal operating temperature. Turn ignition switch to LOCK position. Allow engine to cool for 15 minutes. Turn ignition switch to RUN position. Using scan tool, observe oil level display. If scan tool does not display OK, go to step 3). If scan tool displays OK, system is okay at this time.

Engine Oil Pressure Sensor Diagnosis

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
2. Retrieve DTCs. If DTCs do not exist, go to next step. If any DTCs exist, see DIAGNOSTIC TROUBLE CODES then perform appropriate DTC(s) test. See «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
3. Turn ignition switch to RUN position. If engine oil pressure light illuminates, go to next step. If engine oil pressure light does not illuminate, go to step 16).
4. Check engine oil level. If oil level is okay, go to next step. If oil level is not okay, go to step 11).
5. Using a manual oil pressure gauge, check engine oil pressure. If engine oil pressure is correct, go to next step. If engine oil pressure is not correct, go to step 12).
6. Turn ignition switch to LOCK position. Disconnect engine oil pressure sensor harness connector. Turn ignition switch to RUN position. Using a test light connected to ground, probe engine oil pressure sensor input circuit (Tan/Black wire) at engine oil pressure sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 9).
7. Using a test light connected to battery voltage, probe engine oil pressure sensor ground circuit (Black/White wire) at engine oil pressure sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 10).
8. Check for poor connection at engine oil pressure sensor. If poor connection does not exist, go to step 13). If poor connection exists, repair as necessary and go to step 16).
9. Check for open or short to ground in engine oil pressure sensor input circuit (Tan/Black wire) between PCM and engine oil pressure sensor harness connectors. Also check for poor connection at PCM. If problem does not exist, go to step 15). If problem exists, repair as necessary and go to step 16).
10. Locate and repair open in engine oil pressure sensor ground circuit (Black/White wire) and go to step 16).
11. Determine cause of low oil level and repair as necessary. After repairs are complete, go to step 16).
12. Determine cause of low engine oil pressure and repair as necessary. After repairs are complete, go to step 16).
13. Check communication circuit for proper operation. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 16).
14. Replace engine oil pressure sensor and go to step 16).
15. Replace PCM and go to next step.
16. Check for proper operation of engine oil pressure light. If light operation is okay, system is okay at this time. If light operation is not okay, go to step 2).

Fuel Level Sensor Diagnosis

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
2. Retrieve instrument panel-related DTCs. If no instrument panel DTCs exist, go to next step. If any instrument panel DTCs exist, perform appropriate DTC test. See «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
3. Connect scan tool to data link connector. Turn ignition switch to RUN position. Using scan tool output control function, perform FUEL GAUGE SWEEP TEST. If fuel gauge sweeps through full range, go to next step. If fuel gauge does not sweep through full range, repair fuel gauge. See «INSTRUMENT PANEL»(/chevrolet/malibu/v-1996-2000/remont/gauges-instrument-panels/#instrument-panel) article in ACCESSORIES/SAFETY EQUIPMENT section.
4. Turn ignition switch to LOCK position. Raise and support vehicle. Disconnect fuel tank harness connector. Connect voltmeter between fuel level sensor input circuit (Purple wire) and fuel level sensor ground circuit (Black/White wire) at fuel level sensor harness connector. Turn ignition switch to RUN position. If voltage does not exist, go to next step. If voltage exists, go to step 6).
5. Check fuel level sensor input and ground circuit for open between fuel level sensor and PCM. If open does not exist, go to step 10). If open exists, repair as necessary and go to step 13).
6. If greater than 5 volts existed in step 4), go to step 11). If 5 volts or less existed in step 4), go to next step.
7. Measure voltage between fuel level sensor input circuit (Purple wire) and ground. If approximately 5 volts exists, go to next step. If approximately 5 volts does not exist, go to step 9).
8. Locate and repair open in fuel level sensor ground circuit (Black/White wire). After repairs are complete, go to step 13).
9. Check fuel level sensor input circuit (Purple wire) for open or short to ground. If problem does not exist, go to step 11). If problem exists, repair as necessary and go to step 13).
10. Replace fuel level sensor and go to step 13).
11. Locate and repair short to voltage in fuel level sensor input circuit (Purple wire). After repairs are complete, go to step 13).
12. Replace PCM and go to next step.
13. Recheck system for proper operation. If system is not operating properly, go to step 2).

Manifold Absolute Pressure (MAP) Sensor

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
2. Check for the following, repair as necessary and go to next step: MAP sensor seal. Damage or disconnected vacuum line. Intake manifold leaks. Vacuum leak at throttle body. Vacuum leaks in EGR system. Faulty PCV system.
3. Disconnect MAP sensor harness connector. Using scan tool, observe MAP sensor parameter. If zero volts is displayed, go to next step. If zero volts is not displayed, go to step 10).
4. Using a test light connected to battery voltage, probe MAP sensor signal circuit (Light Green wire) at map sensor harness connector. Observe MAP sensor parameter on scan tool. If 4.95 volts is displayed on scan tool, go to next step. If 4.95 volts is not displayed, go to step 8).
5. Using a fused jumper wire, connect MAP sensor signal circuit (Light Green wire) and MAP sensor reference voltage circuit (Gray wire) at MAP sensor harness connector. If scan tool displays 4.95 volts, go to next step. If scan tool does not display 4.95 volts, go to step 7).
6. Turn ignition switch to LOCK position. Disconnect PCM harness connectors. Check MAP sensor ground circuit (Orange/Black wire) for open and poor connections. If open or poor connection does not exist, go to step 9). If open or poor connection exists, repair as necessary and go to step 12).
7. Check MAP sensor reference voltage circuit (Gray wire) for open and poor connections. If open or poor connection does not exist, go to step 9). If open or poor connection exists, repair as necessary and go to step 12).
8. Check MAP sensor signal circuit (Light Green wire) for open and poor connections. If open or poor connection does not exist, go to next step. If open or poor connection exists, repair as necessary and go to step 12).
9. Replace MAP sensor and go to step 12).
10. Turn ignition switch to LOCK position. Disconnect PCM harness connector. Turn ignition switch to RUN position. Check MAP sensor signal circuit (Light Green) for short to voltage. If short to voltage does not exist, go to next step. If short to voltage exists, repair as necessary and go to step 12).
11. Replace PCM and go to next step.
12. Start engine and let idle. While observing MAP sensor parameter on scan tool, increase RPM. If MAP sensor valve changes, system is okay at this time. If MAP sensor valve does not change, go to step 2).

MOTORS, RELAYS & SOLENOIDS

Manufacturer does not provide many individual system and component testing. For motor, relay and solenoid testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES under COMPUTERIZED ENGINE CONTROLS. See TESTS W/CODES - 3.1L article.

Idle Air Control (IAC) Motor

See IDLE CONTROL SYSTEM.

A/C Clutch Relay

See A/C-HEATER SYSTEM article in AIR CONDITIONING & HEAT section.

Fuel Pump Relay

See BASIC TESTING - 3.1L article.

SOLENOIDS

All PCM-controlled solenoids should have at least 20 ohms of resistance when checked with positive ohmmeter lead connected to power supply terminal of solenoid and negative ohmmeter lead connected to ground terminal of solenoid. Some solenoids are equipped with internal diodes. On these solenoids, resistance values will differ if ohmmeter test leads are reversed.

FUEL SYSTEM

Note. For fuel system pressure testing, see BASIC TESTING - 3.1L article.

Manufacturer does not provide many individual system and component testing. For fuel system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES - 3.1L article.

Note. Retrieve DTCs and perform appropriate DTC test before performing FUEL INJECTOR CIRCUIT DIAGNOSIS. See TESTS W/CODES - 3.1L article. Also ensure all mechanical and ignition coil/module circuit malfunctions are repairs before performing FUEL INJECTOR CIRCUIT DIAGNOSIS.

IDLE CONTROL SYSTEM

Note. System testing for 3.1L is not available from the manufacturer. For idle control system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES - 3.1L article.

IGNITION SYSTEM

Note. For basic ignition system checks, see BASIC TESTING - 3.1L article.

For ignition system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES - 3.1L article.

EMISSION SYSTEMS & SUB-SYSTEMS

Note. For emission and sub-system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES - 3.1L article.

EVAP CONTROL SYSTEM DIAGNOSIS

Note. Ensure all vacuum line and EVAP system components are not damaged or missing before proceeding with this test.

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
2. Turn ignition switch to LOCK position. Remove fuel filler cap. Connect scan tool to data link connector. Turn ignition switch to RUN position. Observe fuel tank pressure on scan tool. If fuel tank pressure is zero in. H2O, go to next step. If fuel tank pressure is not zero in. H2O, perform DTC P0453 test. See «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
3. Replace fuel filler cap. Using scan tool, command EVAP canister vent valve on. Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to EVAP service port. Apply 5 in. H2O pressure to EVAP system while observing fuel tank pressure on scan tool. If fuel tank pressure is 5 in. H2O, go to next step. If fuel tank pressure is not 5 in. H2O, perform DTC P0452 test. See «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
4. Monitor EVAP pressure gauge on diagnostic station while commanding EVAP canister vent valve off. If EVAP pressure decreases to zero in. H2O within 5 seconds, go to next step. If EVAP pressure does not decrease to zero in. H2O within 5 seconds, perform DTC P0446 test. See «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
5. Start engine. Remove fuel filler cap. Using scan tool output test function, select SEAL SYSTEM and activate. Install fuel filler cap. Switch rotary switch on diagnostic station to PURGE. Run engine at idle while monitoring vacuum gauge on diagnostic station. If vacuum does not increase to greater than zero in. H2O, go to next step. If vacuum increases to greater than zero in. H2O, perform DTC P1441 test. See «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
6. Using scan tool output test function, select SYSTEM PERF and activate. Switch rotary switch on diagnostic station to PURGE. Run engine at 2500 RPM for at least 10 seconds while monitoring vacuum gauge on diagnostic station. If vacuum increases to greater than -5 in. H2O, system is okay at this time. If vacuum does not increase to greater than -5 in. H2O, perform DTC P0440 test. See «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.

AIR Pump (Belt-Driven)

Accelerate engine to approximately 1500 RPM and observe airflow from hoses. If airflow increases as engine is accelerated, pump is working properly. If airflow does not increase, check hoses, pump belt tension, leaky valves or defective air injection pump.

Check Valve

Detach check valve and blow through valve in direction of check valve flow (to cylinder head). Attempt to suck air back. Replace valve if airflow is allowed against the direction of flow.

EXHAUST GAS RECIRCULATION

Manufacturer does not provide many individual system and component testing. For EGR system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES - 3.1L article.

Exhaust System Check

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
2. Remove heated oxygen sensor. Install exhaust backpressure tester in place of oxygen sensor. Start engine and let idle. If pressure reading is not 1.25 psi or greater go to next step. If pressure reading is 1.25 psi or greater go to step 4).
3. Increase engine speed to 2000 RPM. If pressure reading is greater than 3 psi go to next step. If pressure reading is not greater than 3 psi go to step 6).
4. Check exhaust system for crushed pipe, internal muffler damage or heat distress. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 6).
5. Replace catalytic converter and go to next step.
6. Operate vehicle within conditions under which original symptom was noted. If system operate properly, system is okay at this time. If system does not operate properly, go to step 2).

Fuel Tank Pressure Sensor Diagnosis

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
2. Disconnect fuel tank pressure sensor harness connector. Measure voltage at reference voltage circuit (Gray wire) at fuel tank pressure sensor harness connector. If about 5 volts does not exist, go to next step. If about 5 volts exists, go to step 5).
3. Check for poor connection at PCM. If poor connection does not exist, go to next step. If poor connection exists, go to step 12).
4. Check fuel tank pressure sensor reference voltage circuit (Gray wire) for open between PCM and fuel tank pressure sensor harness connector. If open does not exist, go to step 8). If open exists, go to step 12).
5. Remove fuel filler cap. Using 2 fused jumper wires, connect reference voltage and signal circuits between fuel tank sensor and fuel tank pressure sensor harness connector. Measure voltage at ground terminal at fuel tank pressure sensor. If 1.3-1.7 volts exists, go to next step. If 1.3-1.7 volts does not exist, go to step 13).
6. Check fuel tank pressure sensor signal circuit (Dark Green wire) for poor connection at PCM. If poor connection does not exist, go to next step. If poor connection exists, go to step 11).
7. Check fuel tank pressure sensor signal circuit (Dark Green wire) for open and short between PCM and fuel tank pressure harness connectors. If open or short exists, go to step 12). If open or short does not exist, go to step 14).
8. Check fuel tank pressure sensor ground circuit (Black wire) for poor connection at PCM. If poor connection does not exist, go to next step. If poor connection exists, go to step 11).
9. Check fuel tank pressure sensor ground circuit (Black wire) for open between PCM and fuel tank pressure harness connectors. If open exists, go to step 12). If open does not exist, go to step 14).
10. Check for poor connection at fuel tank pressure sensor. If poor connection exists, go to next step. If poor connection does not exist, go to step 13).
11. Repair poor connections as necessary and go to step 15).
12. Repair open or short as necessary and go to step 15).
13. Replace fuel tank pressure sensor and go to step 15).
14. Replace PCM and go to next step.
15. Turn ignition switch to LOCK position. Remove gas cap. Connect scan tool to data link connector. Turn ignition switch to RUN position. Observe fuel tank pressure on scan tool. If zero in. H2O is displayed, go to next step. If zero in. H2O is not displayed, go to step 2).
16. Replace gas cap. Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to EVAP service port. Using scan tool, command EVAP canister vent valve on. Using diagnostic station, pressurize EVAP system to 5 in. H2O. Observe fuel tank pressure on scan tool. If 5 in. H2O is displayed, system is okay at this time. If 5 in. H2O is not displayed, go to step 2).

Required Service

The PCV system may require service for obstructions if any of the following conditions exist

1. Rough idle.
2. Stalling or slow idle speed.
3. Oil leaks.
4. Oil in air cleaner.
5. Sludge in engine.

A leaking PCV valve or hose could cause

1. Rough idle.
2. Stalling.
3. High idle speed.

If engine idles rough, check for clogged PCV valve or plugged or broken hoses BEFORE adjusting idle. Check PCV valve application to ensure correct valve is fitted. Replace PCV valve if required.

Checking PCV Valve Function

1. Remove PCV valve from rocker cover. Run engine at idle. Place thumb over open end of valve to check for vacuum. If there is no vacuum at valve, check for obstruction in manifold port, hoses or PCV valve. Repair or replace as necessary.
2. Turn engine off. Remove PCV valve. Shake valve and listen for rattle of check valve inside. If a clear rattle is not heard, replace PCV valve.
3. Visually inspect valve for varnish or deposits which may make PCV valve operation sticky or restricted, or cause incomplete seating of valve. Replace if necessary.
4. An engine must be sealed for PCV system to function as designed. If leakage, sludging or dilution of oil is noted and PCV system is functioning properly, check engine for cause and repair as required to ensure PCV system will continue to function properly.
5. An engine operating without any crankcase ventilation can be damaged, so it is important to replace PCV valve and air cleaner breather (if equipped) at regular intervals (at least every 30,000 miles). Check all hoses and clamps for failure or deterioration.

MISCELLANEOUS CONTROLS

Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

TRANSMISSION

Note. Computerized transmission controls are also covered in greater detail in TRANSMISSION SERVICING - A/T article in AUTOMATIC TRANS SERVICE section manual for domestic vehicles. For component circuit identification, see wiring diagram in WIRING DIAGRAMS - 3.1L article.

Converter Clutch Solenoid

Disconnect harness connector to Torque Converter Clutch (TCC) solenoid. Measure resistance between appropriate TCC solenoid terminals. Solenoid resistance should be greater than 20 ohms.

Note. Some solenoids may have an internal pressure switch in series with the solenoid winding and will not show continuity until that pressure switch is applied by transmission hydraulic pressure.

Converter Lock-Up Signal At Transmission

1. Warm engine to operating temperature. Raise vehicle and support drive wheels. Support suspension where necessary to prevent damage to drive axles.
2. Disconnect converter clutch connector at transmission. Connect a test light across appropriate converter clutch harness terminals. Start engine and place transmission in Drive. Accelerate vehicle to 45 MPH and note test light.
3. If test light is off, check solenoid power supply wire of harness for open or short to ground. Check ground circuit for open between harness connector and PCM. If harness is okay, see CONVERTER LOCK-UP SIGNAL FROM PCM.

Converter Lock-Up Signal From PCM

1. Warm engine to operating temperature. Raise vehicle and support drive wheels. Support suspension where necessary to prevent damage to drive axles.
2. Connect a test light to battery voltage. Touch TCC control driver terminal with test light. Accelerate vehicle to 45 MPH and note test light. If test light does not illuminate, problem is a faulty PCM connector or PCM.

PCM CONTROLLED TACHOMETER

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
2. Check instrument cluster. See «INSTRUMENT PANEL»(/chevrolet/malibu/v-1996-2000/remont/gauges-instrument-panels/#instrument-panel) article in ACCESSORIES/SAFETY EQUIPMENT in section. If instrument panel is okay, go to next step.
3. Turn ignition switch to LOCK position. Disconnect PCM connector. Turn ignition switch to RUN position. Measure voltage between ground tachometer control circuit (White wire) at PCM harness connector. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 7).
4. Set DVOM to 10-amp scale. Check current between ground and tachometer control circuit (White wire) at PCM harness connector. Monitor reading for about 2 minutes. DVOM should read less than .05 amps. If reading is as specified, go to step 12). If reading is not as specified, go to next step.
5. Turn ignition switch to LOCK position. Disconnect instrument cluster harness connectors, but leave PCM connector disconnected. Measure voltage between ground and tachometer control circuit (White wire) at PCM harness connector. If zero volts exists, go to step 17). If voltage exists, go to next step.
6. Locate and repair short to voltage in tachometer control circuit between instrument panel and PCM harness connectors. After repairs are complete, go to step 19).
7. Check ignition feed fuse for instrument panel cluster. 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. After repairs are complete. replace fuse and go to step 19).
9. Disconnect instrument cluster connectors. Turn ignition switch to RUN position. Measure voltage between ground and ignition feed circuit (Pink wire) at instrument cluster harness connector. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 16).
10. Check tachometer control circuit (White wire) for open or short to ground, between instrument cluster and PCM harness connectors. If open or short exists, repair as necessary and go to step 19). If open or short does not exist, go to next step.
11. Check tachometer and ignition feed circuits for poor connection at instrument panel cluster and PCM. If problem exists, repair as necessary and go to step 19). If problem does not exist, go to step 17).
12. Turn ignition switch to LOCK position. Connect PCM harness connectors. Disconnect instrument cluster connectors. Turn ignition switch to RUN position. Connect a test light between tachometer control circuit and ignition feed circuit at instrument panel harness connector. Start engine. If test light flashes, check for shorted component or circuit in the output driver circuit. Check for faulty instrument cluster. If test light does not flash, go to next step.
13. If test light illuminates constantly, go to next step. If test light does not illuminate, go to step 15).
14. Locate and repair the following circuit conditions: Short to ground in crankshaft position sensor feed circuit. Open in camshaft position sensor ground circuit. Poor connection at crankshaft position sensor. After repairs are complete, go to step 19).
15. Check for poor connection at PCM. If problem does not exist, go to step 18). If problem exists, repair as necessary and go to step 19).
16. Locate and repair open in instrument cluster ignition feed circuit. After repairs are complete, go to step 19).
17. Repair or replace instrument cluster as necessary. After repairs, go to step 19).
18. Replace PCM and go to next step.
19. Start engine. Observe tachometer. If tachometer is operating properly, system is okay at this time. If tachometer is not operating properly, repair instrument cluster as necessary.

PCM CONTROLLED GENERATOR

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
2. Turn ignition switch to RUN position. If charging light illuminates, go to next step. If charging light does not illuminate, go to step 4).
3. Start engine. If charging light does not go out, go to step 5). If charging light goes out, go to step 21).
4. Turn ignition switch to LOCK position. Disconnect generator harness connectors. Turn ignition switch to RUN position. If charging light illuminates, go to step 6). If charging light does not illuminate, go to step 7).
5. Turn ignition switch to LOCK position. Connect scan tool to data link connector. Turn ignition switch to RUN position. Ensure all accessories are off. Observe generator voltage on scan tool. If battery voltage is displayed, go to step 8). If less than battery voltage is displayed, go to step 9).
6. Using a test light connected to ground, probe charging light signal circuit at generator harness connector. If test light illuminates, go to step 10). If test light does not illuminate, go to step 11).
7. Replace or repair instrument cluster and/or charging light bulb as necessary. After repairs are complete, go to step 21).
8. Using scan tool, check GEN F valve. If 5 percent is displayed, go to step 7). If 5 percent is not displayed, go to step 12).
9. Turn ignition switch to LOCK position. Disconnect generator harness connectors. Turn ignition switch to RUN position. Using a test light connected to battery voltage, probe charging light signal circuit at generator harness connector. If test light illuminates, go to step 13). If test light does not illuminate, go to step 14).
10. Locate and repair short to ground in charging light control signal circuit and go to step 21).
11. Replace generator and go to step 21).
12. Turn ignition switch to LOCK position. Disconnect generator harness connectors. Turn ignition switch to RUN position. Using a test light connected to battery voltage, probe generator field circuit at generator harness connector. If test light illuminates, go to step 15). If test light does not illuminate, go to step 16).
13. Locate and repair short to ground in field circuit and go to step 21).
14. Measure voltage at charging light signal circuit at generator harness connector. If 4.5 volts or greater exists, go to step 17). If 4.5 volts or greater does not exist, go to step 18).
15. Locate and repair short to ground in field circuit. After repairs are complete, go to step 21).
16. Locate and repair poor connection and/or open in field circuit. After repairs are complete, go to step 21).
17. Measure voltage at battery voltage supply circuit at generator harness connector. If battery voltage exist, go to step 11). If battery voltage does not exist, go to step 19).
18. Check for poor connection and/or open in battery voltage supply circuit. If poor connection and/or open does not exist, go to step 20). If poor connection and/or open exists, repair as necessary and go to step 21).
19. Locate and repair poor connection and/or open in battery voltage supply circuit. After repairs are complete, go to step 21).
20. Replace PCM and go to next step.
21. Operate vehicle under condition under which original symptom was noted. If system does not operate properly, go to step 2).

Warning Light Diagnosis

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l) article.
2. Check instrument cluster. See «INSTRUMENT PANEL»(/chevrolet/malibu/v-1996-2000/remont/gauges-instrument-panels/#instrument-panel) article in ACCESSORIES/SAFETY EQUIPMENT in section. If instrument panel is okay, go to next step.
3. Turn ignition switch to LOCK position. Disconnect PCM connector. Turn ignition switch to RUN position. Measure voltage between affected PCM output circuit at PCM harness connector and ground. See diagram in «WIRING DIAGRAMS - 3.1L»(/chevrolet/malibu/v-1996-2000/remont/wiring-diagrams-engine-performance/#engine-performance-wiring-diagrams-31l) article. If battery voltage does not exist, go to step 7). If battery voltage exists, go to next step.
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. Turn ignition switch to LOCK position. Disconnect instrument cluster harness connectors, but leave PCM connector disconnected. Measure voltage between affected PCM output circuit and ground. If zero volts exists, go to step 15). If voltage exists, go to next step.
6. Locate and repair short to voltage in affected PCM output circuit. After repairs are complete, 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 connectors. Turn ignition switch to RUN position. Measure voltage between ignition feed circuit for instrument panel cluster indicator lights and ground. If battery exists, go to next step. If battery voltage does not exist, go to step 14).
10. Check affected PCM output circuit for an open or short to ground. If open or short exists, repair as necessary and go to step 17). If open or short does not exist, go to next step.
11. Check affected PCM output circuit and ignition feed circuit for poor connection at instrument panel cluster and PCM. If problem exists, repair as necessary and go to step 17). If problem does not exist, go to step 15).
12. Turn ignition switch to LOCK position. Connect PCM harness connectors. Disconnect instrument cluster connectors. Turn ignition switch to RUN position. Connect a test light between affected PCM output circuit and ignition feed circuit at instrument panel harness connector. Using a scan tool, perform OUTPUT TESTS 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 not flash on and off, go to next step.
13. Check affected PCM output circuit for poor connection to PCM. If problem exists, repair as necessary and go to step 17). If problem does not exist, go to step 16).
14. Locate and repair open in ignition feed circuit to instrument panel cluster indicator lights. After repairs are complete, go to step 17).
15. Repair or replace instrument cluster as necessary. After repairs, go to step 17).
16. Replace PCM and go to next step.
17. Using scan tool, operate affected warning light. If warning light does not operate properly, go to step 3).

A/C COMPRESSOR CLUTCH CONTROLS

Note. For A/C clutch circuit testing, see A/C-HEATER SYSTEM article in the AIR CONDITIONING & HEAT section. See wiring diagram in WIRING DIAGRAMS - 3.1L article for terminal and wire color identification.

To provide improved idle quality, improved Wide Open Throttle (WOT) performance and A/C system protection, the compressor clutch is controlled by PCM.

For proper control of cooling fans, compressor clutch and Idle Air Control (IAC) valve, a refrigerant pressure sensor is used. PCM uses signals provided by sensor to monitor high and low side refrigerant pressures. If PCM detects a fault in refrigerant pressure circuit, compressor clutch will be disabled.

The A/C clutch relay is controlled by PCM. This allows PCM to raise idle speed before engaging compressor clutch, or disable compressor clutch during WOT, high engine RPM, high power steering loads and hot engine restarts. PCM also disables compressor clutch if coolant temperature becomes excessive. To locate A/C clutch relay, see A/C CLUTCH RELAY LOCATION table.

A/C CLUTCH RELAY LOCATION

Note. To help save diagnostic time, check for blown fuses or fusible links before proceeding with any testing. If fuses are blown, locate and repair short circuit before replacing fuses. Ensure all related relay and wire harness connections are clean and tight. Repair as necessary.

ELECTRIC COOLING FAN CONTROL

Note. For electric cooling fan circuit testing, see AIR CONDITIONING & HEAT section. See wiring diagram in WIRING DIAGRAMS - 3.1L article for terminal and wire color identification.

All FWD and some RWD vehicles use an electric cooling fan. The electric cooling fan is used for radiator and A/C condenser cooling. Cooling fan operates when A/C is on and when engine coolant temperature exceeds a specific value. One or more cooling fan relays may be used. For cooling fan relay location, see COOLING FAN RELAY LOCATION table.

COOLING FAN RELAY LOCATION

To help save diagnostic time, ALWAYS check for blown fuses or fusible links before proceeding with any testing. If fuses are blown, locate and repair short circuit before replacing fuses. Ensure all related relay and wire harness connections are clean and tight. Repair as necessary. For component location and terminal and wire color identification, see wiring diagram in WIRING DIAGRAMS - 3.1L article.

COMPONENT LOCATIONS

Note. Component location illustrations are not available for Malibu.

COMPONENT LOCATIONS (VIN M)

See also:
• BASIC TESTING - 3.1L
• TESTS W/CODES - 3.1L
• WIRING DIAGRAMS - 3.1L
• AUTO TRANS DIAGNOSIS - 4T40-E (3.1L)
• SENSOR RANGE CHARTS - 3.1L
• INSTRUMENT PANEL
• A/C-HEATER SYSTEM
• POWERTRAIN CONTROL MODULE (PCM) CONNECTOR I.D.