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 can not currently be duplicated, or the DTC diagnostic table indicates the fault not present at this time.
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Preliminary Checks
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| • | Refer to Important Preliminary Checks in
Symptoms . |
| • | 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. |
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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:
| • | Connectors that are poorly mated. |
| • | Terminals that are not fully seated in the connector (backed out). |
| • | Terminals that are not properly formed or damaged (may be due to improper diagnostic probing procedures). |
| • | Poor terminal retention (male to female connection). |
| | Checking for proper terminal retention requires the use of the
J-38125 Terminal Repair Kit. |
| • | Poor terminal to wire connections. |
| | Checking for poor terminal to wire connection requires removing the wire / terminal from the connector body. Refer to Wiring Repairs in Wiring Systems. |
| • | Wires that are broken inside the insulation. |
| • | 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 Connector Repairs in Wiring Systems for the proper procedures to use when making a circuit repair.
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Road Test
| The following tests should be performed with two people, in order to ensure the safe operation of the vehicle.
| • | Drive the vehicle while monitoring the suspect circuit with a scan tool
J 39200 or a Digital Multimeter (or an equivalent) 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 multimeter 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 monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If the DTC appears in the Not Ran Since Code Cleared list, the DTC
diagnostic has not yet run. When the DTC does not appear in the Not Ran Since Code Cleared list, the DTC diagnostic has run. If the MIL is NOT ILLUMINATED and there is no PENDING DTC Status in DTC Information, the DTC diagnostic has passed. DTCs MUST BE CLEARED
in order to view the CURRENT STATUS of the Not Ran Since Code Cleared list. DO NOT FORGET that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for CURRENT
or PENDING status, in order to determine the outcome of the diagnostic test involved. |
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Scan Tool
| The scan tool features that can be used to locate an intermittent conditions include the following:
| • | 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
data values taken from a similarly equipped known good vehicle. |
| • | Freeze Frame / Failure Records data feature |
| | 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,
engine parameters are also stored. This stored information can be reviewed and compared to the typical
Engine Scan Tool Data List values or data values taken from a similarly equipped known good vehicle. |
| | Freeze Frame / Failure Records data will be erased when DTC Information is cleared either by scan tool clearing or by disconnection of the control modules (ECU, VCM / PCM or ECM) power supply. |
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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. |
| • | Ignition control (IC) wires routed near the generator or near secondary ignition system wires and components. |
| • | Ignition system secondary voltage that is arcing and shorting to ground. |
| • | Poor ignition control circuit or ignition module grounds. |
| • | A MIL control circuit that is intermittently shorting to ground. |
| • | Faulty diodes in the generator or charging system circuits. |
| • | The improper installation of add-on electrical devices. These can include the following: |
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Loss of DTC Memory
| In order to check for proper DTC Memory function perform the following procedure:
- Observe the Conditions For Running The DTC for the TP Sensor Circuit Low Voltage DTC.
- Disconnect the TP sensor connector.
- Operate the vehicle within the Conditions For Running The DTC.
- The MIL should illuminate upon completion of all the Conditions For Running The DTC. Two key cycles or drive trips may be required.
- A TP Sensor Circuit Low Voltage DTC should be stored in the PCM and remain in memory when the ignition is turned OFF.
Failure to store a DTC or failure of the DTC to remain in memory may indicate a faulty PCM.
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Additional Checks
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| • | Check for faulty PCM grounds. Refer to
Cell 20: Power and Ground
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| • | 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: |
| • | If the intermittent fault is suspected to involve a particular sensor or component, observe the sensor or component display on a scan tool while moving connectors and wiring harnesses related to the sensor or component. A change in the scan tool
display can indicate the location of the fault. |
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