GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Malibu 🢒 Engine 🢒 Engine Controls - 3.1L 🢒 Intermittent Conditions

A problem may or may not turn on the Malfunction Indicator Lamp (MIL) or store a DTC. DO NOT use the Diagnostic Trouble Code (DTC) charts for intermittent problems. The fault must be present to locate the problem.

Most intermittent problems are caused by faulty electrical connections or wiring. Perform a careful visual/physical check for the following conditions:

    •  Poor mating of the connector halves or a terminal not fully seated in the connector (backed out). Refer to Intermittents and Poor Connections Diagnosis , Connector Repairs and Wiring Repairs in Wiring Systems.
    •  Improperly formed or damaged terminal. Refer to Intermittents and Poor Connections Diagnosis , Connector Repairs and Wiring Repairs in Wiring Systems.
    •  All connector terminals in the problem circuit should be carefully checked for proper contact tension. Refer to Intermittents and Poor Connections Diagnosis , Connector Repairs and Wiring Repairs in Wiring Systems.
    •  Poor terminal to wire connection. This requires removing the terminal from the connector body to check. Refer to Intermittents and Poor Connections Diagnosis , Connector Repairs and Wiring Repairs in Wiring Systems.

Road test the vehicle with a J 39200 Digital Multimeter (DMM) connected to a suspected circuit. An abnormal voltage when malfunction occurs is a good indication that there is a fault in the circuit being monitored.

Use a scan tool to help detect intermittent conditions. The scan tool has several features that can be used to locate an intermittent condition. Use the following features to find intermittent faults:

    •  The Snapshot feature can be triggered to capture and store engine parameters within the scan tool when the malfunction occurs. This stored information then can be reviewed by the service technician to see what caused the malfunction.
    •  Using a Scan Tools Freeze Frame data or Failure Records data can also aid in locating an intermittent condition. Review and record the information in the freeze frame or failure record associated with the intermittent DTC being diagnosed. The vehicle can be driven within the conditions that were present when the DTC originally set

An intermittent MIL (Service Engine Soon) with no stored DTC may be caused by the following:

    •  Ignition coil shorted to ground and arcing at ignition wires or plugs.
    •  MIL (Service Engine Soon) wire to PCM shorted to ground. Refer to Intermittents and Poor Connections Diagnosis , Connector Repairs and Wiring Repairs in Wiring Systems.
    •  Poor PCM grounds, refer to Power and Grounding Component Views in Wiring Systems.

Check for improper installation of electrical options such as lights, cellular phones etc. Route Ignition Control (IC) Module wiring away from secondary ignition wires and ignition coils. Check all wires from the PCM to the ignition control module for poor connections.

Visual/Physical Check

Several of the symptom procedures ask for a Careful Visual/Physical Check. This step is extremely important it can lead to correcting a problem without further checks and can save valuable time. This check includes:

    •  The PCM grounds for being clean, tight, and in their proper location. Refer to Power and Grounding Component Views in Wiring Systems.
    •  Vacuum hoses for splits, kinks, and proper connections, as shown on the Vehicle Emission Control Information label Check thoroughly for any type of leak or restriction. Refer to Emission Hose Routing Diagram .
    •  The Mass Air Flow (MAF) sensor installation. The arrows on the plastic portion of the sensor must point toward the engine.
    •  The air intake ducts for being collapsed or for having damaged areas.
    •  Air leaks at throttle body mounting area, Mass Air Flow (MAF) sensor, and the intake manifold sealing surfaces.
    •  The ignition wires for cracking, hardness, proper routing and carbon tracking.
    •  The engine harness wiring and terminals for proper connections, pinches or cuts. Refer to Connector Repairs and Wiring Repairs in Wiring Systems.