Checking Wiring and Components

Checking Resistance Or Continuity
Checking a portion of the wiring harness or a component as shown indicates whether or not there is a continuous conductive path - whether current can flow between the two test points. The example illustrates troubleshooting the Close Throttle Position switch and the Wide Open Throttle Position switch in the fuel injection system.

CAUTION:
Resistance measurements and continuity checks must always be made with all power to the circuit or component switched OFF. When testing continuity in a circuit that is always powered (fuse/relay panel "30" circuit for example) disconnect the battery before testing.
Always use a digital (low current) meter. An ohmmeter, or the Ohms scale of a multimeter, measures resistance by passing a small amount of current through the circuit or component being checked. Improper testing may damage sensitive electronic components.
Direct contact with meter probes at the connector terminals can easily damage the small contacts, causing poor connections and risking future intermittent malfunctions.
Special Tools include adapters for making test connections safely and preventing connector damage. See Tools and Equipment.

Example 1: Checking A Closed Throttle Position Switch

Testing For Resistance Or Continuity:

Continuity (approximately 0 ohm):
Little or no resistance indicates that there is a continuous conductive path between the two test points. As shown, this is correct for the normally Closed Throttle Position switch in the Closed Throttle Position (switch not actuated). Also check that the switch opens (no continuity) when actuated by the throttle.

No Continuity:
There is resistance to current flow through the switch. In the example, this indicates that the normally Closed Throttle Position switch or the wires between it and the connector (t3) are malfunctioning.

Example 2: Checking A Wide Open Throttle Position Switch

Testing For Resistance Or Continuity:

Continuity (approximately 0 ohm):
Little or no resistance indicates that there is a continuous conductive path between the two test points. In the example, this indicates that the normally Wide Open Throttle Position switch is malfunctioning.

No Continuity:
There is no connection-an open circuit. As shown, this is correct for the normally Wide Open Throttle Position switch. Also check that the switch closes, completing the circuit, when actuated by the Wide Open Throttle Position switch.