Troubleshooting

GENERAL INFORMATION

WARNING: Read the safety precautions (see Section 14) before starting work.

The following tests are intended for checking basic electrical circuits and must not be used to check sensitive electrical circuits (such as the ABS system), especially if the circuit contains an electronic control unit.

A typical electrical circuit consists of an electrical component, switches, relays, motors, fuses, fusible links or circuit breakers, and wires and connectors that join all the components together and connect them to the battery and to vehicle ground. To simplify fault finding, Subsection 14.20 contains wiring diagrams of the vehicle electrical system. Before checking a faulty circuit, first study the circuit schematic to understand which components it consists of.

A fault can be located faster if you determine which components of the circuit are working normally.

If several components or circuits fail at the same time, the problem is most likely a blown fuse or a poor ground connection, since one fuse often protects several circuits.

Electrical system problems are usually caused by simple faults such as corroded or loose connections, a blown fuse, a blown fusible link, or a faulty relay (for the relay test procedure, see Subsection 14.3).

Visually inspect the condition of all fuses, wires and connectors in the faulty circuit before checking other components of this circuit.

If you intend to use test equipment, use the circuit schematics to determine which connections must be checked to locate the fault.

The main tools required to locate a fault in an electrical circuit are a voltmeter (or a 12-volt test lamp with connecting leads), a continuity tester, an ohmmeter (for measuring resistance), a battery with connecting leads and a jumper wire, preferably with a circuit breaker, which can be used to connect in parallel to the circuit.

Before starting to locate a fault using test equipment, study the circuit schematics to determine the connection points.

To locate a loose connection or a short circuit point (usually caused by a poor or contaminated connection or damaged insulation), you can shake the wire by hand to see if the circuit fails when the wire moves. In this way, you can find the point with a loose connection or the point where the short circuit occurs. This test method can be used together with the other tests described in the following subsections.

In addition to poor connection problems, an electrical circuit can have two other main faults: an open circuit or a short circuit.

An open circuit may be caused by a broken wire or a missing connection somewhere in the circuit that prevents current from flowing. An open circuit will cause a component to stop working, but it will not blow the fuse of that circuit.

A short circuit is caused by contact somewhere in the circuit that causes the current flowing through the circuit to flow into another circuit, most often to ground. A short circuit is usually caused by damaged insulation that allows a live wire to touch either another wire or a grounded component, such as the body. A short circuit will blow the fuse of the affected circuit.