ECU Test Harness Installation

Before troubleshooting this system, ensure that other elements that affect engine performance such as the emission control components and ignition system are operating properly. Also, check valve clearances, air cleaner, PCV valve, ignition timing, vacuum and centrifugal advance and spark plugs. The following conditions and/or problems may not all be exhibited on any particular model and/or engine.





Test Harness Use
If the inspection for a particular system requires the ECU test harness remove the drivers seat, then remove the three screws on the [1][2]control unit cover and remove the cover to expose the control unit connectors. Connect the test harness to the control unit.





CAUTION:
- Puncturing the insulation on a wire can cause poor or intermittent electrical connections.
- For testing at connectors other than the ECU test harness, bring the tester probe into contact with the terminal from the connector side of wire harness connectors in the engine compartment. For female connectors, just touch lightly with the tester probe and do not insert the probe.

Flow Chart Use
A flow chart is designed to be used from start to final repair. It's like a map showing you the shortest distance. But beware; if you go off the "map" any where but a "shop" symbol, you can easily get lost.

[START] (bold type)
Describes the conditions or situation to start a troubleshooting flow chart.
[ACTION]
Asks you to do something; perform a test, set up a condition, etc.

Asks you about the result of an action, then sends you in the appropriate troubleshooting direction.
[STOP] (bold type)
The end of a series of actions and decisions, describes a final repair action and sometimes directs you to (bold an earlier part of the flow to confirm your repair.

NOTE:
- "Open" and "Short" are common electrical terms. An open is a break in a wire or at a connection. A short is an accidental connection of a wire to ground wire. In simple electronics, this usually means something won't work at all. In complex electronics (like electronic control units), this can sometimes works, but not the way it's supposed to.
- If no trouble is found by the end of a particular Output inspection, return to the symptom-to-sub system chart and try the next-likely cause.
- A shorted wire may damage the emission control unit.