Flow of Diagnosis

START HERE

Begin by reviewing the Initial Inspection and Diagnostic Overview. Initial Inspection and Diagnostic Overview

The System Precheck MUST be the FIRST test performed Reading and Clearing Diagnostic Trouble Codes

Failure to do so may result in an incorrect diagnosis, wasted time and unnecessary replacement of good components. The System Pre-Check is used to screen the vehicle for relatively simple diagnostic repairs such as loose connectors, blown fuses, etc. However, the System Pre-Check is also used to prepare the vehicle for further diagnostics. In addition, anti-lock brake warning indicator concerns are addressed in this check.

PINPOINT TESTS
CAUTION:
- Do not proceed to ANY pinpoint test unless directed to do so.
- The two circuits between the anti-lock brake control module and each brake anti-lock sensor are twisted together at intervals of approximately one turn per 25 mm (1 inch). When circuits are repaired, be sure to restore the turns to ensure proper shielding.

NOTE:
- The connector numbers found in the Pinpoint Tests may not match the numbers found in the Wiring Diagrams. The pin numbers will be the same.
- Parameter Identification (PID) is a mode selectable from the scan tool. This mode will allow you to monitor control module input and output states.

These tests are specific for each diagnostic trouble code (DTC). However jumping to a pinpoint test as the first step can be misleading. The tests have been written under the assumption that the System Pre-Check has been performed and passed. At times, running completely through the pinpoint test will not lead to concern resolution. Often, the concern is due to an intermittent connection, termination, or circuit concern. Review Intermittent Diagnostics when situations like this arise. Component Tests and General DiagnosticsThroughout the pinpoint tests, many of the values given depend on the presence of a good chassis ground available at pins 1, 14, 15, and 27. Once the breakout box, adapter and overlay are installed, check for continuity between pins 1, 14, 15 and 27 and ground. The chassis ground must be verified before any measurement involving those pins can be made. At any time, a known good chassis ground may be substituted when directed to use pins 1, 14, 15 and 27.

EQUIPMENT
Refer to Tools and Equipment for proper tools required to perform the tests. Tools and EquipmentRefer to equipment instructions for proper tool usage and procedures.