Important Guidelines When Performing Test Procedures

WHAT IS A DIAGNOSTIC TEST PROCEDURE?
A diagnostic test procedure is a systematic method of checking the function of a vehicle control system to determine if it is working properly. The diagnostic test procedure is also a systematic method of determining where the problem Is.

IMPORTANT GUIDELINES WHEN PERFORMING TEST PROCEDURES
1. Each category has many tests. Always start at test one of a category. Starting at any other test may give incorrect results.
2. Accurately answer each question in a test and only perform those tests required by that answer.
3. At the end of each test (or when specifically directed) reconnect all wires and hoses.
4. The vehicle being tested must have a fully charged battery.
5. As you test, visually inspect connectors and wiring of the circuit being worked on.
6. Use only a fused jumper wire on all tests.
7. Never use a test lamp in place of a voltmeter.
8. If you must crank the engine with the coil wire disconnected, make sure you ground the wire or hold it no more than 1/4 inch from ground. Failure to do this could result in damage to ECU electronics.
9. MMC vehicles use an air flow meter for air volume measurement. All air intake hoses must be in place and secure for proper engine performance and testing.
10. Avoid long tests on injectors to prevent flooding or hydrostatic engine lock.
11. Fuel lines are under pressure even when the engine is off. Use only the proper special tool for fuel pressure measurement and observe all warnings and cautions.
12. when a vehicle has multiple fault codes always start with the lowest fault code number first. This is important!