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. Only perform the steps indicated under action required. It is not necessary to perform all the steps in a test. If you do, the problem will not be found.
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 single module engine controller (SMEC) 60-way and 14-way connectors, 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, shorting or energizing terminals which are connected to the SMEC. Such mistakes can possibly damage the SMEC 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 SMEC.
11. Avoid long checks for fuel flow from the injector to prevent flooding or hydrostatic damage to the engine.
12. Remember, this is a pressurized fuel supply system. After testing make sure all fittings are restored and torqued before starting the engine. Once the engine is started, check for leaks at all lines on which tests were performed.
13. If more than one fault code appears, review the test indication column for multiple code combinations. If one cannot be found, then handle each fault code as a separate failure.
14. Some tests require the use of a digital or analog voltmeter. Make sure you use the correct one or you may see incorrect results. If a test does not specify the type of voltmeter then either one may be used.