Checking Wiring and Terminals. Intermittent Faults

Checking wiring and terminals. Intermittent faults

Inspect terminals visually





Note! When checking the engine control module (ECM), do not remove the control module from the car before the main relay has interrupted the power supply. This may take up to 4 minutes after the ignition has been switched off and the engine cooling fan (FC) has stopped running.

Inspect the terminals visually when checking, or taking readings from, opened connectors.
For repair of wiring and terminals, reference the relevant wiring diagram(s).

Checks:
- Check for oxidation. This can cause poor connections in the terminals
- Check for damage to pins and terminals. Check that they are properly inserted into the connector. Check that the cable is properly connected to the pin or terminal. Check pins and terminals particularly carefully
- Using a loose male connector, test to see if the female connector provides a good contact and that the pin remains in place when the male connector is pulled lightly
- Shake the cable lightly and pull on connectors during measurement to locate damage.

Open-circuit, intermittent faults




An open-circuit in a cable will be indicated by the loss of a function (or functions).
Chafed and broken leads are common causes of faults.
For repair of wiring and terminals, reference the relevant wiring diagram(s).

Checks:
- Disconnect the connectors at both ends of the cable.
Check the cables visually according to Inspect terminals visually.
Connect an ohmmeter between the ends of the cable.
The ohmmeter should read approximately 0 ohms if there is no open-circuit in the cable.
Shake the cable lightly and pull on connectors during measurement to locate the damage.
If the reading is not correct. Replace the cable and / or continue according to Contact resistance and oxidation.




Always check the control module and control module box connectors to ensure that their pins and sockets are not bent or damaged, this may cause faults.
Check pins and terminals particularly carefully.

Short-circuit to ground, intermittent faults




A short-circuit between a live cable and ground is often indicated by the loss of a function or a fuse blowing when a current is passed through the cable.
For repair of wiring and terminals, reference the relevant wiring diagram(s).

Checks:
- Check the cables visually according to Inspect terminals visually.
Activate all switches and sensors in the circuit. Check whether the fuse blows
- Disconnect the connectors in the circuit to ensure that they do not affect readings.
Connect an ohmmeter between cable and ground.
The ohmmeter should read infinite resistance if no components are connected.
Shake the cable lightly and pull on connectors during measurement to locate the damage.
If the reading is not correct, replace the cable and / or continue according to Contact resistance and oxidation.

Short-circuit to supply voltage, intermittent faults




A short-circuit between a cable and supply voltage is often indicated by the loss of a function or a fuse blowing when a current is passed through the cable.
For repair of wiring and terminals, reference the relevant wiring diagram(s).

Checks:
- Check the cables visually according to Inspect terminals visually.
Use a voltmeter to take readings at various points in the circuit while operating switches and sensors.
The voltmeter reading depends on the circuit being tested and the positions of switches and sensors. Use the wiring diagram to determine the correct voltage in the circuit.
Use an ohmmeter between the suspect cables to detect short-circuits between them.
The ohmmeter should read infinite resistance between cables not connected to each other in the circuit.
Shake the cable lightly and pull on connectors during measurement to locate the damage.
If the reading is not correct. Replace the cable and / or continue according to Contact resistance and oxidation.

Loose connections (terminals)




For repair of wiring and terminals, reference the relevant wiring diagram(s).
Loose connections in terminals may be caused by oxidation of the pins and sockets, or by a faulty connection of a cable to its cable terminal.
Loose connections produce the same faults as an intermittent open-circuit in a cable.

Checks:
- Inspect terminals visually according to Inspect terminals visually.
Continue according to Contact resistance and oxidation.

Contact resistance and oxidation




In theory, the resistance across contacts, leads and terminals should be 0 ohms. However, there is always some resistance due to terminal oxidation.
If resistance is too great there will be function problems. The magnitude of the resistance before it causes a malfunction depends on the circuit load. A guideline would be a few ohms.

Cleaning female socket terminals and male pin terminals





Note! Do not apply rust solvent spray or grease to the catalyst monitor sensor or instrument cluster connectors.

- Ignition off
- Disconnect the battery negative terminal
- Use compressed air to clean the disconnected connector
- Apply rust solvent spray 1161422 to the disconnected connectors
- Blow clean using compressed air.

Greasing female terminals





Note! Do not fill the protective cover with grease.

- Press grease, P/N 1161417-9, into the terminals directly from the tube
- Check that all the cavities in the connectors are filled
- Use a loose male pin to ensure that contact in sockets is good. The pin should remain in position when pulled gently.