FA. Checking Wiring and Connections

F. Other electrical fault tracing

FA. checking wiring and connections






Many electrical system faults can be due to faulty wiring and poor connections. Faults of this type may be due to interference from other electrical Systems, physical damage or chemical action.

FA1

Inspect terminals visually.

Terminals should be inspected visually in the case of all measurements and checks in which connectors are opened.


Checks:

- Inspect for oxidation, which may cause poor contact in the terminals
- Inspect the terminal pins and sockets are not damaged and that they are correctly locked in to the connector. The copper conductor must be properly connected to the cable terminal. Pay extra attention to the pin and socket for the DTC stored.
- Use a spare male terminal to test the contact on a female terminal and that the cable terminal is securely in place.

FA2

Circuit break (Open-circuit)






A break or open circuit in a cable is indicated when a function stops operating.

Chaffed or broken cables and terminals that have come loose are all common causes of faults in electrical systems.



Checks:

- Disconnect connectors at both ends of a cable.
- Inspect terminals visually as per FA1.

Use an ohmmeter between the ends of the cable. The ohmmeter should read approx. 0 Ohms if the cable is not damaged.



Checking intermittent breaks (open circuit):

- Inspect cables visually as per FA1.
- Shake leads slightly and pull terminals gently during measurement to identify which cable is damaged.


FA3

Short circuit to ground

A short circuit between a voltage carrying cable in the circuit and ground is usually indicated by the fuse blowing when the power is turned on or loss of function operability.


Checks:






- Activate all switches and sensors in the circuit and check if the fuse blows.
- Disconnect component connectors on the circuit to ensure that they do not affect measurements.


Use an ohmmeter to measure between the cables and ground.
Instrument should read infinity if no components are in circuit.

Checking intermittent short circuit to ground:






- Inspect cable visually as per FA1.
- Shake leads slightly and pull terminals gently during measurement to identify where cable is damaged.



FA4

Short circuit to supply

A short circuit between a cable in the circuit and supply will usually result in the fuse blowing when the power is turned on or loss of function operability.






Checks:

- Use voltmeter to measure at various points on the circuit while activating switches and sensors.

Voltmeter reading will depend on the particular circuit, and status of switches and sensors. Use wiring diagram to determine correct voltage in circuit.

- To locate short circuits between cables use an ohmmeter to measure resistance between suspect cables.

Resistance between leads not connected to each other in the circuit should be infinity.






Checking for intermittent short circuit to supply

- Inspect cable visually as per FA1.
- Shake leads slightly and pull terminals gently during measurement to identify where cable is damaged.


FA5

Loose connections






Poor contact in terminals may be caused by oxidation of the pins and sockets, or by defective connection of a cable to its cable terminal.

Loose connections cause the same fault symptoms as an intermittent break in a cable.


Checks:

- Inspect cable visually as per FA1.
- Shake cable slightly and pull connections gently during measurement to locate faulty connections.
- Pay extra attention to the pins and sockets for the DTC stored.






- Always check the control module and connector on the control module box for bent or damaged pins or sockets.
- Pay extra attention to the pins and sockets for the DTC stored.

NOTE: Always turn off the ignition before removing a control module for inspection.


Contact resistance and oxidation in connections

In theory, the resistance across contacts, leads and terminals should be 0 Ohms. But there is always some resistance due to terminal oxidation.

If the resistance in terminals is too great a malfunction in a component or system will result. Circuit load determines how much resistance there can be in a circuit before it impairs the operation of components or systems. A few Ohms resistance is normally within tolerance levels.

Check

- Inspect terminals visually as per FA1.

Cleaning female socket terminals and male pin terminals






NOTE: Rust solvent spray or grease must not be used on the HO2S sensor connector.

- Ignition OFF
- Disconnect battery negative lead.
- Blow the disconnected connector clean with compressed air
- Spray the disconnected connector with rust solvent 1161422 (1161435 USA/CDN).
- Blow clean with compressed air.

Applying grease to female connectors

NOTE: Do not fill the protective cover with grease.

- Using grease 1161417 directly from the tube, press in to the female connector half.






- Check that all the terminal cavities are filled.







- Use loose male pin to check that contact with sockets is good. Pin should remain in position when pulled gently.