Many intermittent open or shorted circuits are affected by harness/connector movement that is caused by vibration, engine torque, bumps/rough road, etc. In order to duplicate the customer's concern, it may be necessary to manipulate the wiring harness if the malfunction appears to be vibration related. Manipulation of a circuit can consist of a wide variety of actions, including:

All these actions should be performed with some goal in mind. For instance, with a scan tool connected, wiggling the wires may uncover a faulty input to the control module. The snapshot option would be appropriate here. Refer to Scan Tool Snapshot Procedure in Wiring Systems. Another option is, with the component commanded ON and OFF by the scan tool, move related connectors and wiring and observe the component operation. With the engine running, move related connectors and wiring while monitoring engine operation. If harness or connector movement affects the data displayed, component/system operation, or engine operation, inspect and repair the harness/connections as necessary.

You may need to load the vehicle in order to duplicate the concern. This may require the use of weights, floorjacks, jackstands etc. In these cases you are attempting to duplicate the concern by manipulating the suspension or chassis. This method is useful in finding harnesses that are too short and their connectors pull apart enough to cause a poor connection. A Digital Multimeter set to Peak Min/Max mode and connected to the suspect circuit while testing can yield desirable results. Refer to Testing for Electrical Intermittents in Wiring Systems.

Certainly, using the senses of sight, smell, and hearing while manipulating the circuit can provide good results as well.

There may be instances where circuit manipulation alone will not meet the required criteria for the fault condition to appear. In such cases it may be necessary to expose the suspect circuit to other conditions while manipulating the harness. Such conditions would include high moisture conditions, along with exceptionally high or low temperatures. The following discusses how to expose the circuit to these kinds of conditions.

Some compounds possess the ability to conduct electricity when dissolved in water such as ordinary salt. By mixing table salt with water in sufficient quantities, you can enhance the conductive properties of water so that any circuit which may be sensitive to moisture will more readily fail when liberally sprayed with this mixture.

Mixing 0.35L (12 oz) of water with approximately 1 tablespoon of salt will yield a salt solution of 5 percent. Fill a normal spray bottle with this mixture. This mixture is sufficient to enhance the water's own conductivity. This may cause the circuit to fail more easily when sprayed. Once the mixture is completed, spray the suspect area liberally with the solution. Then, while monitoring either a scan tool or Digital Multimeter, manipulate the harness as discussed previously.

If the complaint tends to be heat related, the high temperature condition may be achieved simply by test driving the vehicle at normal operating temperature.

Manipulate the harnesses under high temperature conditions while monitoring the scan tool or Digital Multimeter to locate the fault condition.

Depending on the nature of the fault condition, leaving the car to sit for 3 - 4 hours or getting the customer to drop the vehicle off the night before to sit overnight can have the desired effect.

If this is unsuccessful, use local cooling treatments such as ice. This is ideally suited for localised cooling needs.

Once the vehicle, component, or harness has been sufficiently cooled, manipulate the harness or components in an effort to duplicate the concern.