Engine Controls - 3.9L - Troubleshooting & Diagnosis: Other Chevrolet Uplander I

Identifying Intermittent Conditions

Many intermittent conditions occur with harness or connector movement due to engine torque, rough pavement, vibration or physical movement of a component. Refer to the following for a list to help determine an intermittent condition

1. Moisture and water intrusion in connectors, terminals and components
2. Connector mating
3. Terminal contact
4. High circuit or component resistance-High resistance can include any resistance, regardless of the amount, which can interrupt the operation of the component.
5. Harness that is located too tight or chaffed circuits
6. High or low ambient temperature
7. High or low engine coolant temperatures
8. High underhood temperatures
9. Heat build up in component or circuit due to circuit resistance, poor terminal contact or high electrical load
10. High or low system voltage
11. High vehicle load conditions
12. Rough road surface
13. Electro-magnetic interference (EMI)/circuit interference from relays, solenoids or other electrical surge
14. Incorrect installation of non-factory, aftermarket and after factory add on accessories

If an intermittent is determined, refer to Testing for Intermittent Conditions and Poor Connections for specific strategies in diagnosing intermittent conditions.

Visual/Physical Check

Note. Use the connector test adapter kit J 35616-A for any test that requires probing the following items: The PCM harness connectors The electrical center fuse/relay cavities The component terminals The component harness connector Using this kit will prevent damage caused by the improper probing of connector terminals.

Several of the symptom procedures call for a careful visual and physical inspection. This can lead to correcting a condition without further tests and can save time. This inspection should include the following areas

1. Ensure that the control module grounds are clean, tight and correctly located. Refer to «Master Electrical Component List»(ref-241683-S00068215092006081100000) and «Power and Grounding Connector End Views»(ref-241719-S04638886242006081100000) .
2. Inspect vacuum hoses for splits, kinks and proper connections, as shown on the Vehicle Emission Control Information label. Inspect thoroughly for any type of a leak or a restriction. Refer to «EVAPORATIVE EMISSIONS (EVAP) HOSE ROUTING DIAGRAM»(ref-241687-S22420438352006081100000) .
3. Inspect for a dirty or restricted air filter.
4. Inspect for water intrusion in the mass air flow (MAF)/intake air temperature (IAT) sensor connector, heated oxygen sensor (HO2S) connectors, control module connectors or any other harness connectors.
5. Inspect the air intake ducts, particularly between the MAF sensor and the throttle body for the following conditions: Collapsed Damaged areas Looseness Incorrect installation Leaking
6. Inspect for air leaks at the throttle body mounting area, the MAF sensor and intake manifold sealing surfaces.
7. Inspect the wiring harness for the following conditions: Poor connections Pinches Cuts
8. Inspect for loose, damaged, unseated or missing sensors/components.
9. Inspect terminals for corrosion and correct contact.

Electrical Information Reference

1. «Circuit Testing»(ref-241671-S15536097382006081100000)
2. «Connector Repairs»(ref-241671-S30908621342006081100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000)
4. «Wiring Repairs»(ref-241671-S28487612812006081100000)

Circuit/System Verification

The MIL should turn ON and OFF when commanded with a scan tool.

Repair Procedures

1. Refer to «Control Module References»(ref-241672-S08014971642006081100000) for ECM replacement, setup and programming.
2. Refer to Instrument Panel Cluster (IPC) Replacement .

1. «Circuit Testing»(ref-241671-S15536097382006081100000)
2. «Connector Repairs»(ref-241671-S30908621342006081100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000)
4. «Wiring Repairs»(ref-241671-S28487612812006081100000)
5. «Starting System Description and Operation»(ref-241706-S33625683732006081100000)

Attempt to start the engine. Engine should start and run.

1. «Circuit Testing»(ref-241671-S15536097382006081100000)
2. «Connector Repairs»(ref-241671-S30908621342006081100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000)
4. «Wiring Repairs»(ref-241671-S28487612812006081100000)

1. With the ignition ON, engine OFF, command the fuel pump relay ON and OFF several times using the scan tool output control function. You should either hear or feel the relay click and the fuel pump should turn ON and OFF with each command. If the fuel pump operates continuously, test for a faulty relay or a short to voltage in the supply voltage circuit of the fuel pump.

1. for ECM replacement, setup and programming.
2. Fuel Tank Module Replacement
3. «Relay Replacement (Within an Electrical Center)»(ref-241671-S35940232652006081100000) or «Relay Replacement (Attached to Wire Harness)»(ref-241671-S12712310652006081100000)
4. «Relay Replacement (Within an Electrical Center)»(ref-241671-S35940232652006081100000) or «Relay Replacement (Attached to Wire Harness)»(ref-241671-S12712310652006081100000)

1. «Circuit Testing»(ref-241671-S15536097382006081100000)
2. «Connector Repairs»(ref-241671-S30908621342006081100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000)
4. «Wiring Repairs»(ref-241671-S28487612812006081100000)

1. Turn ON the ignition, with the engine OFF.
2. Command the fuel pump relay ON with a scan tool. If the fuel pump does not operate, refer to «Fuel Pump Electrical Circuit Diagnosis»(ref-241724-S22717874872006081100000) .
3. Turn OFF the ignition.
4. Turn OFF all accessories.
5. Install a J 34730-1A . Refer to «Special Tools Required»(ref-241724-S13976037302007031900000) .
6. Turn ON the ignition, with the engine OFF.
7. Command the fuel pump relay ON with a scan tool.
8. Observe the J 34730-1A with the fuel pump commanded ON. The fuel pressure should be 345-414 kPa (50-60 psi). If the fuel pressure is less than 345 kPa (50 psi), inspect for a restricted fuel feed pipe, poor connections at the harness connectors and ground circuits of the fuel pump or a faulty fuel sender assembly. If the fuel pressure is more than 414 kPa (60 psi), replace the fuel sender assembly.
9. Monitor the J 34730-1A for 1 minute. The fuel pressure should not decrease more than 34 kPa (5 psi). If the fuel pressure decreases more than 34 kPa (5 psi), continue with Circuit/System Testing.
10. Relieve the fuel pressure to 69 kPa (10 psi).
11. Monitor the J 34730-1A for 5 minutes. The fuel pressure should not decrease more than 14 kPa (2 psi). If the fuel pressure decreases more than 14 kPa (2 psi), replace the fuel sender assembly.
12. Remove the J 34730-1A . Refer to «Special Tools Required»(ref-241724-S13976037302007031900000) .
13. Operate the vehicle within the conditions to reproduce the original symptoms.
14. Monitor the O2 and the Fuel Trim parameters with a scan tool. If the scan tool parameters indicate a lean condition, inspect for a restricted fuel feed pipe, poor connections at the harness connectors and ground circuits of the fuel pump or a faulty fuel sender assembly. If the scan tool parameters do not indicate a lean condition, go to «Symptoms - Engine Controls»(ref-241724-S40028774192006081100000) .

1. «FUEL INJECTOR AND FUEL RAIL REPLACEMENT»(ref-241687-S16201871072007030600000)
2. Fuel Sender Assembly Replacement

1. «Circuit Testing»(ref-241671-S15536097382006081100000)
2. «Connector Repairs»(ref-241671-S30908621342006081100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-241671-S27410119602006081100000)
4. «Wiring Repairs»(ref-241671-S28487612812006081100000)

Pressure Drop Calculation

1. Subtract the second pressure reading from the first pressure reading for one fuel injector. The result is the pressure drop value.
2. Obtain a pressure drop value for each fuel injector.
3. Add all of the individual pressure drop values. This is the total pressure drop.
4. Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop. The difference between any individual pressure drop and the average pressure drop should not be more than 20 kPa (3 psi). If the difference between any individual pressure drop and the average pressure drop is more than 20 kPa (3 psi), replace the fuel injector.

Diagnostic Repair Verification

System Verification

1. The fuel sample should be drawn from the bottom of the tank so that any water present in the tank will be detected. The sample should be bright and clear. If the sample appears cloudy or contaminated with water, as indicated by a water layer at the bottom of the sample, perform the Particulate Contaminants in Fuel Testing Procedure. If alcohol contamination is suspected, perform the Alcohol in Fuel Testing procedure.

Fuel System Cleaning

Reference Information

1. «Electronic Ignition (EI) System Description»(ref-241687-S41357313292006081100000)
2. «Ignition System Specifications»(ref-241687-S24517631502006081100000)

1. «SPARK PLUG WIRE REPLACEMENT»(ref-241687-S41806885742007030600000) for spark plug wire replacement
2. «SPARK PLUG REPLACEMENT»(ref-241687-S07054642802007030600000) for spark plug replacement
3. «IGNITION COIL REPLACEMENT»(ref-241687-S11115013492007030600000) for ICM and coil assembly replacement

Conditions for Updating the I/M System Status

Each system monitor requires at least one and sometimes several diagnostic tests. The result of each test is reported by a diagnostic trouble code (DTC). A system monitor is complete when either all of the DTCs composing the monitor have Run and Passed or when any one of the DTCs comprising the monitor has illuminated the malfunction indicator lamp (MIL). Once the system monitor is complete, the I/M System Status display will indicate YES in the Completed column.

For example, when the HO2S Heater Status indicates YES, either all of the oxygen sensor heater tests have passed or one of the tests has illuminated the MIL. If the vehicle has four heated oxygen sensors, either all four heater circuit tests have passed or one of the heater circuit tests has illuminated the MIL. The I/M System Status will indicate NO under the Completed column when any of the required tests for that system have not run. The following is a list of conditions that would set the I/M System Status indicator to NO

1. The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
2. The battery has been disconnected or discharged below operating voltage.
3. The control module power or ground has been interrupted.
4. The control module has been reprogrammed.
5. The control module DTCs have been cleared.

Monitored Emission Control Systems

The OBD II System monitors all emission control systems that are on-board. The OBD II regulations require monitoring of the following

1. The air conditioning system
2. The catalytic converter efficiency
3. Comprehensive component monitoring-Emission related inputs and outputs
4. The evaporative emission (EVAP) system
5. The fuel delivery system
6. Heated catalyst monitoring
7. Misfire monitoring
8. The oxygen sensor system (O2S or HO2S)
9. The oxygen sensor heater system (HO2S heater)

For the specific DTCs required for each system, refer to. Systems such as fuel delivery, misfire and comprehensive components may not be listed in a system status list. These tests run continuously and do not require an I/M System Status indicator.

Review the I/M System Status indicators. All I/M System Status indicators should report YES.

Conditions for Meeting a Cold Start

1. The ignition voltage between 11-18 volts.
2. The barometric pressure (BARO) is more than 75 kPa.
3. The start-up engine coolant temperature (ECT) is between 4-30°C (39-86°F).
4. The start-up intake air temperature (IAT) is between 4-30°C (39-86°F).
5. The difference between the IAT and the ECT is 6°C (10.8°F)
6. The ambient air temperature is between 4-30°C (39-86°F).
7. Fuel level is between 15 and 85 percent
8. Vehicle has NOT been refueled since the last cold start ignition cycle.

Review the I/M System Status indicators. All I/M System Status indicators should report YES.