For 1990-2009 cars

Checks | Action
--- | ---
DEFINITION: The problem may or may not turn ON the MIL or store a DTC. There is a customer concern, but the symptom can not 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 - Engine Controls .

• | The fault must be present in order to be diagnosed correctly with a DTC table. If the fault that set the DTC is intermittent, then the use of DTC tables may result in replacement of good parts.

Electrical Connections or Wiring | Electrical connections and wiring cause most intermittent conditions. Determine which circuit is suspected of having an intermittent condition. This may be indicated by DTCs with a fault not present. Check the suspect circuit for the following conditions:

• | Any connectors that are poorly mated

• | Any terminals that are not fully seated in the connector

• | Any terminals that are not properly formed or damaged

• | A poor male to female connection--Checking for proper terminal retention requires the use of the J-38125 Terminal Repair Kit.

• | Any poor terminal-to-wire connections--Checking for poor terminal-to-wire connections requires removing the wire/terminal from the connector body. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

• | Any wires that are broken inside the insulation

• | A pierced or damaged insulation that allows water or moisture to enter the wiring--The conductor can corrode inside the insulation with little visible evidence. Look for swollen and stiff sections of wire in the suspect circuit.

Refer to Wiring Repairs and to Connector Repairs in Wiring Systems for the proper procedures to use when making a circuit repair.

Road Test | The following tests should be performed with 2 people in order to ensure the safe operation of the vehicle.

• | Drive the vehicle while monitoring the suspect circuit with a scan tool or a DMM connected to the circuit. Look for an abnormal reading or voltage when the malfunction occurs. An abnormal reading on the scan tool or an abnormal voltage on the DMM display is an indication that there may be a malfunction in the circuit that was being monitored.

• | If the intermittent fault sets a DTC, the diagnostic that sets the DTC can be enhanced using Check Mode. Operating the vehicle while in Check Mode can enable certain DTC diagnostics to run faster. Check Mode also turns some B type DTCs to A type DTCs. Refer to Service Bay Test .

• | Certain DTCs must run before I/M system status can be determined. Any DTC that affects the status of an I/M system can be monitored indirectly on the scan tool under the I/M System Information selection. In order to determine which DTCs are associated with a particular I/M system test, refer to Inspection/Maintenance (I/M) System DTC Table . If an intermittent DTC is associated with a particular I/M system, monitoring the I/M system test can indicate whether the diagnostic for that DTC has run. When the I/M system test displays a YES status, indicating that the system diagnostic is complete, check for the applicable DTC in the Last Test Failed screen of the scan tool. If the DTC is not displayed, the diagnostic for that DTC has run and passed, indicating that no malfunction was present this time. All DTCs MUST BE CLEARED in order to view the Current Status of the I/M system tests. Do not forget that the I/M System Information tests only indicate that the test has run, not if the test passed or failed. The Last Test Failed screen must be checked for related DTCs in order to determine the outcome of the diagnostic test involved.

Scan Tool | The scan tool features that can be used to locate an intermittent conditions include the following:

• | The scan tool Snapshot feature--The scan tool Snapshot feature can be triggered to capture and store engine parameters when a malfunction occurs. This stored information can be reviewed and compared to the Typical Scan Tool Data Values or to data values taken from a similarly equipped known-good vehicle.

• | The Freeze Frame/Failure Records data feature--The Freeze Frame/Failure Records are stored when certain DTCs set. They typically include information to aid in reproducing the driving conditions that were present when a DTC is stored. In addition, the engine parameters are also stored. This stored information can be reviewed and compared to the typical Scan Tool Data List values or to data values taken from a similarly equipped known-good vehicle.

| The Freeze Frame/Failure Records data will be erased when DTC Information is cleared either with the scan tool or by disconnection of the control modules ECU, vehicle control module/powertrain control module (VCM/PCM), or engine control module (ECM) power supply.

Intermittent malfunction indicator lamp (MIL) | The following conditions may cause intermittent MIL operation with no DTCs stored:

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

• | Any ignition control (IC) wires routed near the generator or near the secondary ignition system wires and components

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

• | Any poor ignition control circuit or ignition module grounds

• | A MIL control circuit that is intermittently shorting to ground

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

• | The improper installation of add-on electrical devices--These can include the following:

- | Alarm systems

- | 2-way radios

- | Lighting systems

- | Electrical motors

Loss of DTC Memory | In order to check for proper DTC Memory function, perform the following procedure:

1. Observe the Conditions For Running The DTC for the throttle position (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 all the Conditions for Running the DTC. Two key cycles or drive trips may be required.
5. A TP sensor circuit low voltage DTC should be stored in the PCM and remain in memory when the ignition is turned OFF.

A failure to store a DTC or failure of the DTC to remain in memory may indicate a faulty PCM.

Additional Checks |

• | Check for faulty PCM grounds. Refer to Engine Controls Schematics .

• | Check for open diodes (A/C clutch, charging system, etc.) that may cause electrical interference.

• | The improper installation of add-on electrical devices--These can include the following:

- | Alarm systems

- | 2-way radios

- | Lighting systems

- | Electrical motors

• | If the intermittent fault is believed to involve a particular sensor or component, observe the sensor or component display on a scan tool while moving the connectors and the wiring harnesses related to the sensor or the component. A change in the scan tool display can indicate the location of the fault.