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. Most DTCs cause the transaxle to enter limp-in or default mode (see next section on 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 performing Test 1 "Pre-Diagnostic Checkout". Following this test, perform Test 2 "Entering 41TE/AE 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 CCD Bus bias or communication 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/battery in either or both CCD Bus wires
- 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.

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.