Intermittent Conditions

Important: Inspect for improper installation of electrical components if an intermittent condition exists. Inspect for aftermarket theft deterrent devices, lights and cellular phones. Ensure that no aftermarket equipment is connected to the Class 2 circuit. If you can not locate an intermittent condition, a cellular phone signal communication may cause the condition.

Important: The condition may or may not turn ON the Malfunction Indicator Lamp (MIL) or store a DTC. DO NOT use the Diagnostic Trouble Code (DTC) tables for intermittent conditions. The fault must be present in order to locate the condition.

Faulty electrical connections or wiring cause most intermittent conditions. Perform a thorough visual/physical inspection for the following conditions:

^ Poor mating of the connector halves or a terminal not fully seated in the connector body (backed out). Refer to Repairing Connector Terminals in Disgrams.
^ An improperly formed or damaged terminal. Refer to Repairing Connector Terminals in Diagrams.
^ Reform or replace connector terminals in the circuit in order to insure proper contact tension. .
^ Poor terminal to wire connection requires removing the terminal from the connector body in order to inspect. Initial Inspection and Diagnostic Overview

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

Use a scan tool in order to help detect intermittent conditions. The GM Techline equipment (Scan Tool) has several features that you can use to locate an intermittent condition. Use the following features to find intermittent faults:

^ You can trigger the Snapshot feature in order to capture and store engine parameters within the scan tool when the malfunction occurs. You can then review this stored information in order to see what caused the malfunction.
^ Using the Scan Tool Freeze Frame or Failure Records option can also aid in locating an intermittent condition. Review and capture the information in the Freeze Frame and/or Failure record associated with the intermittent DTC being diagnosed. Drive the vehicle in the conditions that were present when the DTC originally set.

Important: If the intermittent condition exists as a start and stall, search for DTCs related to the vehicle theft deterrent system. Inspect for improper installation of electrical options such as lights, cellular phones etc. Any of the following may cause an intermittent Malfunction Indicator Lamp (MIL) with no stored DTC:

^ The ignition coils shorted to a ground, arcing at the ignition wires or the spark plugs.
^ The PCM grounds.
^ The Ignition Control (IC) wires for being routed to close to the secondary ignition wires, coils, or the generator. Ensure that all of the circuits from the PCM to the ignition coils have good connections.
^ An open diode across the A/C compressor clutch and other open diodes.

Use the following tables when diagnosing a symptom complaint:

^ Hard Start
^ Surges/Chuggles
^ Lack of Power, Sluggishness, or Sponginess
^ Detonation/Spark Knock
^ Hesitation, Sag, Stumble
^ Cuts Out, Misses
^ Poor Fuel Economy
^ Poor Fuel Fill Quality
^ Rough, Unstable, or Incorrect Idle and Stalling
^ Dieseling, Run-On
^ Backfire