Diagnostic Starting Point - Automatic Transmission V6
The transmission diagnostic procedure is organised in a logical structure that begins with the Diagnostic System Check and as such must always be used as the starting point. The Diagnostic System Check directs the technician to the logical steps necessary to diagnose a transmission driveability fault condition.
Test Modes
Tech 2 has six test modes for diagnosing the transmission. To get to these various test modes, on Tech 2 select: Diagnostics / Model Year / Model / Transmission / Automatic Transmission
and follow Tech 2's prompts. This will then display the following menu operations.
Diagnostic Trouble Codes
If Diagnostic Trouble Codes is selected, a selection list is displayed which contains:
| • | Read DTC Information - Once selected, both current and history Diagnostic Trouble Codes (DTCs) stored in the transmission control module will be displayed. |
| • | Clear Engine & Transmission DTC(s) - Once selected, DTCs stored in the transmission control module (TCM) and engine control module (ECM) memory may be cleared. |
| • | Freeze Frame / Failure Records - Shows Freeze Frame / Failure Records information. Freeze Frame / Failure Records are types of snapshots stored in the memory of the TCM and contain data parameters from the TCM at the time the DTC is set. |
Important: For a complete list of TCM DTCs, refer to 4.6 Diagnostic Trouble Code List.
Snapshot
In this test mode, Tech 2 captures TCM data before and after a forced manual trigger.
Additional Functions
If Additional Functions is selected, a selections list is displayed which contains:
System Identification: In this mode, Tech 2 will display the transmission identification screen. The following items will be displayed; Identifier, Partnumber, Hardware Partnumber, Alpha Code, Software Version Number, Software Partnumber, VIN Digit 1-10, VIN Digit 11-17.
Programming
If Programming is selected, a selection list is displayed which contains:
Reset TAP Cells - This test allows the user to reset the Transmission Adapt (TAP) cells by pressing the Reset soft key.
Important: Upon resetting the TAP cells the TCM loses all learnt adaptive functions. When the vehicle is first driven after this, the shifts may be harsh. This harshness will ease as the TCM relearns the TAP cells.
Diagnostic Trouble Code Tables
The Diagnostic System Check and the DTC list, directs the technician to the appropriate diagnostic trouble code (DTC) tables if there is a DTC currently stored in the TCM.
The diagnostic tables locate a faulty circuit or component through a logic based on the process of elimination. These diagnostic tables are developed with the following assumptions:
| • | The vehicle functioned correctly at the time of assembly, |
| • | There are no multiple faults, and |
| • | The problem currently exists. |
Understanding and the correct use of the diagnostic tables are essential to reduce diagnostic time to prevent misdiagnosis.
Multiple DTCs Fault Condition
Some fault conditions trigger multiple component DTCs even if the fault condition exists only on a single component. If there are multiple DTCs stored in the TCM, the service technician must view and record all DTCs logged.
Relationship between the logged DTCs can then be analyzed to determined the source of the fault condition. Always begin the diagnostic process with the DTC table of the fault condition that may trigger other DTCs to set.
The following fault conditions may trigger multiple DTCs:
| • | A fault in the serial data communication circuit. |
| • | A system voltage that is too low may cause incorrect transmission tem operation or transmission component malfunction. |
| • | A system voltage that is too high may damage the TCM and/or other components. |
| • | Fault condition in the TCM Read Only Memory (ROM) or Random Access Memory (RAM). |
| • | Fault condition in the TCM internal circuitry or programming. |
| • | Improperly connected sensor or component wiring connector. |
If there are no obvious faults to begin a multiple DTC fault condition diagnostic procedure, refer to the Conditions for Running the DTC in each diagnostic.
