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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 GMC C Sierra - 2WD (CNG) 🢒 Engine 🢒 Engine Controls - 6.0L 🢒 Intermittent Conditions

Checks

Action

DEFINITION: The problem may or may not turn ON the MIL or store a DTC. If a DTC was stored and the DTC diagnostic table indicates the fault is not present an Intermittent Condition is indicated.

Preliminary Checks

Refer to Important Preliminary Checks in Symptoms - Engine Controls .

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.

Inspect the suspect circuit for the following conditions:

    • Connectors poorly mated.
    • Terminals not fully seated in the connector -- backed out.
    • Terminals not properly formed or damaged -- usually due to improper diagnostic probing procedures.
    • Poor terminal retention.
        Testing for terminal retention requires the use of the J-38125 Terminal Repair Kit.
    • Poor terminal to wire connection.
        Inspecting for poor terminal to wire connection requires removing the wire / terminal from the connector body.

Road Test

Drive the vehicle while monitoring the suspect circuit with the scan tool or the J 39200 DMM connected to the circuit. An abnormal voltage or scan tool reading indicates the suspect circuit and a possible circuit condition.

Scan Tool

The scan tool features that can be used to locate an intermittent conditions source 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 Engine Scan Tool Data List 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 Engine Scan Tool Data List 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 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.
    • The improper installation of add-on electrical devices. These can include the following:
       - Lighting systems
       - 2-way radios
       - Electrical motors
    • Ignition control (IC) wires routed near the generator or secondary ignition system wires and components.
    • The ignition system secondary voltage shorted to ground.
    • Poor control or ignition module grounds.
    • The MIL control circuit intermittently shorted to ground.

Loss of DTC Memory

In order to test for proper DTC Memory function perform the following:

  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 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 control module and remain in memory when the ignition is turned OFF.

Failure to store a DTC or for the DTC to remain in memory may indicate a faulty control module.

Additional Checks

Test for open diodes -- A/C clutch, etc. -- that may cause electrical interference.

Vehicle Data Recorder

The J 42598 Vehicle Data Recorder is connected to the data link connector (DLC) and sent with the customer. The captures data for later retrieval and analysis by the technician. Refer to the vehicle data recorder user instructions for more information.