Testing For An Intermittent Condition

INTRODUCTION:  Duplicating the conditions under which the stored DTC set is very important when diagnosing an intermittent condition. Review the Freeze Frame Data (if available), Event Data (if available), Environmental Data, and the When Monitored information for the DTC being diagnosed. The customer can also provide vital information regarding the conditions when the DTC set.

If possible, pay particular attention to the ambient air temperature when the DTC set. Electrical connections, such as wire terminal connections, solder joints, and printed circuit board traces will expand and contract due to temperature changes. If the DTC was set in extreme cold conditions, the vehicle may need to be tested in extreme cold conditions.

IMPORTANT:  Poor wire harness terminal connections are a big contributor to intermittent electrical connections. Follow the directions below to help identify the source of the intermittent electrical condition:

• Record all DTCs on the repair order.
• Run a Vehicle Scan Report.
• With a scan tool, check all electronic control modules for software updates that are related to the customer complaint.
  • Update the electronic control module(s) as needed.
• Use the Search function in TechCONNECT to search for any related information under SERVICE ACTIONS/TIPS.
  • Perform any Service Bulletins or other procedures that may apply.
• With the scan tool, perform any applicable System Tests or Actuations to the component(s) that may cause the DTC to set.
• For Communication DTCs, perform the scan tool LOSS OF COMM TEST. This will force the modules on the CAN C bus to continuously ping each other once every second. Wiggle the applicable wires while reading the NUMBER OF NO RESPONSES. A value above 0 indicates the location of a circuit fault.
• For Relay related DTCs, with the scan tool, actuate the Relay and wiggle the related wiring harness and connectors to attempt to interrupt the actuation.
• Review any applicable scan tool Freeze Frame, Event and Environmental Data information and attempt to duplicate the conditions under which the DTC set. If needed, operate the vehicle.
• Monitor the scan tool parameters related to the DTC while wiggling the related wiring harness and connectors. Look for the DTC status or parameter values to change.
  • Using a data recorder and/or a lab scope may help diagnose intermittent conditions.
• Using the wiring diagrams as a guide, visually inspect the related wiring harness and check for the following:
  • Proper wiring harness routing.
  • Chafed, pierced, pinched or open wiring harness insulation.
  • Partially broken wires.
  • Wiring or wiring strands broken inside of the insulation.
• If multiple DTCs are set, use the wiring diagrams and inspect the following for poor connections or corrosion:
  • Module power and ground circuits.
  • Sensor reference and return circuits.
  • Chassis grounds.
  • Any common circuits.
• Disconnect all the related module, component and in-line wiring harness connectors and perform the following steps:
  1. Visually inspect the connector casings, locks, and weather-proof seals for any damage or water intrusion.
  2. Visually inspect for broken, bent, pushed out, or corroded terminals.
  3. Visually inspect the connectors and terminals for overheating due to a poor connection (terminals may be discolored due to excessive current draw).
  4. Verify the terminals in the connectors are fully seated into the connector/component and properly locked into position.
  5. Inspect the male and female connector terminals for proper terminal tension (drag test).
  6. Connect all the related module, component and in-line wiring harness connectors and verify they are fully seated.
• Check for any aftermarket accessories and verify they are installed and operate correctly. If needed, disconnect them to verify they are not the cause of the problem.
• For additional information on performing circuit tests. Refer to STANDARD PROCEDURE .
• Before releasing the vehicle, perform the following steps:
  1. Verify all connectors are fully seated, connected and properly locked.
  2. With the scan tool, erase DTCs.
  3. Using the recorded Freeze Frame Data (if available), Event Data (if available), Environmental Data, and the When Monitored information for the DTC being diagnosed, operate the vehicle in the conditions that set the DTC.
  4. With the scan tool, read DTCs.
     • If the DTC sets, refer to the appropriate DTC procedure.