Self Diagnostics

The TCM continuously monitors system performance. When a problem is detected in the electrical control or hydraulic portion of the system, the TCM stores a Diagnostic Trouble Code (DTC). Most DTCs cause the transaxle to enter limp-in or default mode (see Default Desensitization). With the DRB Scan Tool in the Transmission portion of the diagnostic program, it constantly monitors the transmission control module to see if the system is in limp-in mode. If the transaxle is in limp-in, the DRB will flash the red LED. Always begin by reading the diagnostic trouble codes using the DRB Scan Tool. This procedure begins with Test 1 A - Entering Diagnostic Tests. This test will direct you to the specific test(s) that must be performed. If more than one trouble code exists, diagnostic priority should be given to the most recent code.

If there is a communication bus problem, DTCs will not be accessible until the problem is fixed. The DRB will display an appropriate message. The following is a list of possible causes for a bus problem:
- Open or short to ground or battery in either or both Bus wires (only one wire for 1998 PCI bus)
- Internal failure of any control module connected to the bus

The CCD Bus should have +2.5 volts on CCD+ and +2.5 volts on CCD-. The bus error message displayed by the DRB should be helpful in diagnosing the CCD Bus.

The PCI Bus should have above 0.6 volts with the ignition on, headlamps on and all doors open.

Each diagnostic trouble code is diagnosed by following the specific testing sequence found in this publication. These 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 to diagnose an individual code. In certain test procedures, codes are used as a diagnostic tool.