By Larry Turay
In the previous issue, wiring harness issues were discussed. The subject of harness issues continues with a look at connectors and connections either in the harness or at a control module or component. Often a component or module is replaced without resulting in any change in the condition or elimination of the DTCs. In addition to the wiring harness, the connectors must be inspected carefully and tested. It is recommended that technicians use the listed resources found in the service manuals whenever appropriate to assist them in the diagnostic process. Circuit testing procedures are found in the troubleshooting section of the service information references.
It is a good practice to have a procedure to follow when troubleshooting electrical problems to help find the problem as quickly as possible with the least amount of time and disassembly.
A proven diagnostic process is the 7-step diagnostic test. The 7 troubleshooting steps are:
• Verify the complaint.
• Obtain pertinent information.
• Determine potential causes.
• Narrow the list of potential causes.
• Test to determine the root cause.
• Repair the root cause and any progressive damage it caused.
• Verify the complaint has been eliminated.
ATTENTION! Keep in mind, when applying pertinent information, use both the OEM and VENDOR data.
Using the service manual information, determine and investigate the following circuit characteristics. Though the symptoms may vary, basic electrical failures are generally caused by:
• Loose connections: open/high resistance in terminals, splices, connectors and
• Improper connector/harness routing: assembly, opens/shorts and high resistance in
terminals, splices, connectors and grounds.
• Corrosion and wire damage: opens/shorts and high resistance in terminals, splices,
connectors and grounds.
• Component failure: opens/shorts and high resistance in relays, modules, switches,
• Aftermarket (vendor) equipment: installation of non-OEM equipment may affect the
normal operation of other electrical systems. (Read more)