Wiring

B. Checking wiring and data link connectors (DLCs)

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


B1 Inspect connections visually
B2 Short-circuit
B3 Short-circuit to ground
B4 Short-circuit between leads
B5 Poor contact (intermittent open-circuit)
B6 Contact resistance in terminal connections
B7-B1O Checking DLC

Intermittent faults

Faulty wiring and terminal connections are the commonest source of intermittent faults. Check for faults of this nature as described below.





B1
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.
- Ensure that male pins are intact and that copper conductors are connected securely to pins.





B2
Open-circuit

An open-circuit in a lead will be indicated by the loss of a function (or functions).
Chafed and broken leads are the commonest fault sources.
Check:

- Disconnect connectors at each end of lead.

Measure resistance by connecting ohmmeter to each end of lead.
Instrument should read approx. 0 Ohms if lead is intact. Intermittent open-circuit

- Inspect lead visually as per B1.

Shake lead and pull terminals gently during measurement to identify location of fault.





B3
Short-circuit to ground

A short-circuit between a live lead and ground will usually result in failure of the fuse or loss of a function (or functions) when the lead is made live.
Checks:

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

Use ohmmeter to measure resistance between lead and ground.
Instrument should read infinity if no components are in circuit




Intermittent short-circuit to ground

- Inspect lead visually as per B1. Shake lead and pull terminals gently during measurement to identify location of fault.





B4
Short-circuit to supply

A short-circuit between a live lead and the supply will usually result in failure of the fuse or loss of a function (or functions) when the lead is made live. This type of fault may cause the circuits to activate' each other.
Check:

- Use voltmeter to measure at various points of the circuit while operating switches and sensors.

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

- To locate short-circuits, use ohmmeter to measure resistance between suspect leads.

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





Intermittent short-circuit to supply

- Inspect lead visually as per B1.
- Shake lead and pull terminals gently during measurement to identify location of fault.





B5
Poor contact in terminals

Poor contact in terminals may be caused by oxidation of the pins and sockets, or by faulty connection of the leads.
Poor contact causes the same symptoms as an intermittent open-circuit.
Check:

- Inspect lead visually as per B1.
- Shake lead and pull terminals gently during measurement to identify location of fault.

B6
Contact resistance and oxidation

In theory, the resistance across contacts, leads and terminals should be 0 Ohms. However, a certain resistance is always present due to faulty connections, oxidation of the terminals and wear.
The function in question will be impaired if the value becomes excessive. The value which is tolerable without impairment of the function is dependent on the circuit load. A typical value is a few Ohms.
Checks

- Inspect terminals visually as per B1.





Cleaning of male pins and female sockets

Caution!
Rust remover or grease must not be applied to HO2S connectors!

- Disconnect battery ground lead.

Spray connector halves with rust remover, P/N 1161034-2.

- Blow clean with compressed air.





Greasing connectors

Caution!
Do not fill protective sleeve with grease.

- Press grease, PIN 1161417-9, into female sockets directly from tube.
- Check that cavities in all connector halves are filled.





- Use separate male pin to check that contact with female sockets is firm and that pin remains in place when lead is pulled gently.