Diagnostic Aids

WARNING: This page is about a different car, the 1996 Mercury Villager and 1995 Mercury Villager. However, it is still accessible from the selected car via links, so may be relevant.

Following information should be noted during testing:

Ensure 5-amp ENGINE fuse is okay.
All voltage readings given in test procedures are based on values obtained using a standard DVOM.
When instructed to inspect a wiring harness, perform both a visual inspection and a continuity test.
When making voltage checks, ground connections should be made at negative battery terminal or cast iron surface of engine.
When making measurements on a wiring harness or connector, perform a wiggle test while measuring.
When checking voltage, ground reading is defined as value of less than one volt. Battery voltage is defined as value of 10-14 volts.
DO NOT measure voltage or resistance at PCM. DO NOT connect any test light unless specified in testing procedure. All measurements are made by probing rear of connector.
Isolate both ends of a circuit and turn ignition off when checking continuity.
An open circuit is defined as a resistance reading of greater than 5 ohms. This specification tolerance may be too much for some items in EEC system. If resistance approaches 5 ohms, always clean suspect connector and coat it with protective dielectric silicone grease. A short is defined as a resistance reading of less than 10,000 ohms to ground, unless stated otherwise.
Test procedures are intended to identify faulty components or wiring while fault is present. If complaint is an intermittent condition, refer to TESTS W/O CODES article in the ENGINE PERFORMANCE section.