Electronic Diagnosis and Testing

Suitable instruments for fault-tracing in the car's electrical system are an Intelligent Saab Tester (ISAT) scan tool, or equivalent, and a suitable voltmeter and ohmmeter.

Use an ISAT or a voltmeter for measuring the voltage at various points in a circuit.

Use an ISAT or an ohmmeter to check for short circuits and open circuits in wiring, connectors switches and contacts. The ohmmeter must not be used when measuring components which contain semi-conductors, like relays with a time function and control modules.

When you measure resistance, the car's battery must be disconnected, as the instrument has a built-in battery which feeds current to the circuit being measured. This will ensure that no current is already flowing through the circuit and that a correct reading will be obtained.