Intermittent Conditions. Chevrolet Metro 1999

For 1990-2009 cars

Checks | Action
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DEFINITION: The problem may or may not turn ON the MIL or store a DTC. There is a customer concern, but the symptom cannot currently be duplicated, or the DTC diagnostic table indicates the fault not present at this time.

Preliminary Checks

• | Refer to Important Preliminary Checks in Symptoms

• | The fault must be present in order to be correctly diagnosed. If the fault is intermittent, the use of DTC tables may result in the unnecessary replacement of good parts.

Electrical Connections or Wiring

Usually, intermittent conditions are caused by electrical connections or by wiring.

Determine which circuit is suspected of having an intermittent condition. Any DTCs set with a fault not present can indicate the intermittent.

Check the suspected circuit for the following conditions:

• | Incorrectly-mated connectors

• | Incorrectly seated connectors

• | Incorrectly formed terminals or damaged terminals

• | Poor terminal tension

| Use the terminal repair kit in order to check J-38125 for the correct terminal tension.

• | Poor terminal-to-wire connections

| Checking for incorrect terminal-to-wire connection requires removing the wire or the terminal from the connector body. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

• | Broken wires inside the insulation.

• | Damaged insulation that allows moisture to enter the wiring.The conductor can corrode inside the insulation with little visible evidence. Look for swollen sections or for stiff sections of the wire in the suspected circuit.

Refer to Wiring Repairs and Connector Repairs to in Wiring Systems.

Road Test

Perform the following tests with two people, in order to ensure the safe operation of the vehicle.

• | Drive the vehicle while monitoring the suspected circuit with a scan tool J 39200 or with a digital multimeter. If the malfunction occurs, look for an abnormal scan tool reading or for an abnormal voltage. An abnormal reading or an abnormal voltage indicates that there may be a malfunction in the circuit.

• | If the intermittent causes a DTC to set, monitor the diagnostic on the scan tool. The test has not run if the DTC appears in the Not Ran Since Code Cleared. If the DTC does not appear under Not Ran Since Code Cleared, the DTC diagnostic has run. If the MIL is not illuminated and there is not a pending DTC Status in DTC Information, the DTC diagnostic has passed. Clear the DTCs in order to view the current status of the Not Ran Since Code Cleared list. The Not Ran Since Code Cleared list only indicates the test has run, not if the test has passed or failed. Check the DTC Information for CURRENT status or for PENDING status, in order to determine the result of the test.

Scan Tool

Use the following scan tool features in order to locate an intermittent condition:

• | The snapshot feature

| The scan tool snapshot feature can be triggered to capture the engine parameters if a malfunction occurs. This stored information can be reviewed and compared to the Typical Scan Tool Data Values or the data values of a similarly equipped vehicle.

• | The Freeze Frame and Failure Records

| The Freeze Frame and Failure Records are stored if certain DTCs set. The Freeze Frame Failure Records can aid in reproducing the driving conditions that were present when a DTC set. The engine parameters are also stored. This information can be compared to the typical data values or Engine Scan Tool Data List to the values from a similarly equipped vehicle.

| The Freeze Frame and Failure Records will be erased when the DTC Information is cleared.

Intermittent Malfunction Indicator Lamp (MIL)

The following conditions may cause intermittent MIL operation without any DTCs set:

• | A faulty relay, a control-module-driven solenoid, or a switch that causes an electrical system interference. Usually, the symptom will occur when the faulty component is operating.

• | An ignition control (IC) wire that is routed near to the generator or near the secondary ignition system components.

• | An ignition system secondary voltage that is arcing and is shorted to ground.

• | A faulty ignition control circuit or a faulty ignition module ground.

• | An MIL control circuit that is shorting to ground.

• | Any faulty diodes in the generator or in the charging system circuits.

• | The incorrect installation of add-on electrical devices. Check any of the following add-on devices:

- | Alarm systems

- | 2-way radios

- | Lighting systems

- | Electrical motors

Loss of DTC Memory

In order to check for the correct DTC Memory function, perform the following procedure:

1. Observe the Conditions for Running the DTC for the TP Sensor Circuit Low Voltage DTC.
2. Disconnect the TP sensor connector.
3. Operate the vehicle within the Conditions For Running The DTC.
4. The MIL should illuminate upon completion of the Conditions For Running The DTC. Two key cycles or drive trips may be required.
5. A TP Sensor Circuit Low Voltage DTC should remain in memory after the ignition is OFF.

Failure to store a DTC or a DTC that does not remain in memory may indicate a faulty PCM.

Additional Checks

•

Check for faulty PCM grounds. Refer to

#### Cell 21: Power and Ground

.

• | Check for open diodes that may cause electrical interference.

• | The incorrect installation of add-on electrical devices. Check the following devices:

- | Alarm systems

- | 2-way radios

- | Lighting systems

- | Electrical motors

• | If the intermittent fault involves a particular component, observe the component display on a scan tool while moving the related connectors and the related wiring. A change in the scan tool display can indicate the location of the fault.