Engine Controls - 3.5L - 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. Electromagnetic 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 «Emission Hose Routing Diagram»(ref-241686-S08700489162006081100000) and «Evaporative Emissions (EVAP) Hose Routing Diagram»(ref-241686-S16796803672006081100000) .
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. «Control Module References»(ref-241672-S08014971642006081100000) for ECM replacement, setup and programming
2. CELL LINK 50650

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)

Attempt to start the engine. The 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. «Manifold Absolute Pressure (MAP) Sensor Replacement»(ref-241686-S05170885732006081100000)
2. «Control Module References»(ref-241672-S08014971642006081100000)

Repair Verification

Diagnostic Repair Verification

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 11.0 and 18.0 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 15-85 percent
8. Vehicle has NOT been refueled since the last cold start ignition cycle.

Review the Inspection/Maintenance (I/M) System Status indicators. All I/M System Status indicators should report YES.