How to Use This Section

Diagnosis of faults is done in three basic steps:

1. Visual inspection
- A careful and thorough visual inspection may quickly identify the cause of a malfunction and eliminate the need for additional diagnostic procedures.
- Diagnosis of vehicle faults always starts with the visual inspection. If the fault is not resolved by the visual inspection, perform the diagnostic test(s).

2. Diagnostic tests
- Each specific fault is diagnosed by following a specific testing sequence. It is not necessary to perform all of the tests to diagnose an individual fault.
- Always begin diagnostic testing with Test 1A. This will direct you to the specific test(s) that must be performed in response to the specific vehicle fault.

3. Verification test
- A verification of system operation must always be performed to ensure that the system is operating normally after the cause of a fault has been found and repaired.

All of the information has been specifically included to assist you to find the cause of a vehicle fault.

- The Helpful Information section contains all of the basic information you will need to perform diagnostic tests using the DRBII.

- Begin by reading the Helpful Information section carefully and thoroughly.

- Included in the Helpful Information are several "HELP" subjects. These provide important basic information about the DRBII, components, connectors, and safety. Reference is made to the Helps within a test procedure when the information is required for correct performance of the test.

Diagnostic Test Procedures

Finding the cause of a vehicle fault is not always easy or quick. However, the diagnostic test procedures have been designed to lead you through the steps necessary to find the cause of a vehicle fault as easily and quickly as possible.

- The diagnostic test procedures contain step by step instructions for how to determine the cause of a vehicle fault. Possible sources of the fault are checked and eliminated one by one.

- The diagnostic tests include a schematic of the electrical circuitry for the system, and illustrations of the system components and connectors to clarify the test steps.

- For instructions on performing test procedures, see "Diagnostic Test Procedures" later in this section.

To successfully perform diagnostic testing, use the information and follow the procedures as presented.