System Description and Functional Operation: Diagnostic Trouble Codes: Overview

DIAGNOSTIC TROUBLE CODES (DTC'S)

Always begin diagnosis by performing a visual inspection,
- check the fluid level and condition and correct as necessary
- check and adjust manual linkage as necessary
- check the electrical connections at the PCM, TCM, TPS, TRS and Transmission solenoids for pushed out or corroded terminals. Make sure all connectors are seated properly.
- test drive the vehicle to verify the customer complaint
- read the DTC's, the DTC will direct you to the specific test(s) in the table of contents that must be performed. If more than one code exists, diagnostic priority should be given to the most recent code.

If there is a CCD bus or communication problem, trouble codes will not be accessible until the problem is repaired. The DRBIII(R) will display an appropriate diagnostic message.

The following is a possible list of causes for a bus problem:
- open in either or both CCD bus wires.
- short to ground on either or both CCD bus wires.
- short to battery on either or both CCD bus wires.
- internal failure of any module or component on the bus

NOTE: THE CCD BUS SHOULD HAVE APPROXIMATELY 2.5 VOLTS ON BOTH WIRES. FOR MORE DETAILED INFORMATION ABOUT DIAGNOSING CCD BUS PROBLEMS, REFER TO THE APPROPRIATE BODY DIAGNOSTIC SYMPTOM.

The P-code, P1698 - No CCD messages from TCM was added in 1997.

This is a powertrain symptom (PCM code) and is diagnosed in powertrain diagnostics symptoms.

Each diagnostic trouble code is diagnosed by following a testing sequence. The diagnostic test procedures contain step-by-step instructions for determining the cause of a transmission diagnostic trouble code. Possible sources of the code are checked and eliminated one by one. It is not necessary to perform all of the tests in this book to diagnose an individual code. In certain test procedures within this book, codes are used as a diagnostic tool.

DTC's which affect vehicle emissions will illuminate the Malfunction Indicator Lamp (MIL). Three consecutive "Good" Euro Stage III OBD trips or clearing the DTC's with a diagnostic tool (DRBIII(R) or equivalent) is required to extinguish the MIL.