Diagnostic Strategies

The following are some guidelines for perfofrming the test procedures:

1. Each category is made up of many tests. Always start at test one of the category. Starting at any other test may give incorrect results.
2. Each test may have many steps and branches. Answer each branch question and perform only those steps required by that answer.
3. At the end of each test (not step) reconnect all wires and hoses, turn the engine off, and reinstall any components that were removed for testing.
4. The vehicle being tested must have a fully charged battery.
5. When performing the cold test, the engine must not be started for at least 7 hours.
6. When performing the warm test, the engine must be at normal operating temperature.
7. When checking for voltage or continuity at the Engine Controller 60-way connector, use the terminal side of the connector not the wire side. Probing the wire side will give inaccurate results, damage the female terminals, and cause failures.
8. Use extreme care when making electrical tests and when disconnecting and re-connecting connectors to prevent accidental grounding, or shorting of terminals. Such mistakes can possibly damage fuses and components such as the Engine Controller and also can cause a second fault that could make diagnosing the original problem more difficult.
9. Under no circumstances should a test light be used in place of a voltmeter because damage to electronic components may occur.
10. If the procedure requires you to crank the engine with the coil wire disconnected, make sure that it is grounded or held a quarter inch away from ground to allow sparking. Failure to do this will erase all fault codes and possibly damage the vehicle electronics.
11. Avoid long checks for fuel flow from the injector to prevent flooding or hydrostatic damage to the engine.
12. If more than one fault message is in memory, always repair the #1 fault message first.