Diagnostic Trouble Codes and Freeze Frames

Diagnostic Trouble Codes And Freeze Frames
When an OBD relevant transmission fault is detected the TCM stores a temporary (Pending) fault code in its memory. An OBD Scan Tool can read this temporary fault code using J1979 mode $07. The temporary fault code is retained until the associated fault counter reaches zero. At the first initialisation of the TCM this counter is pre-loaded with a value of 10. The counter is decremented one count for each successful pass of all the diagnostic tests during a warm-up cycle.

If during the next driving cycle of the vehicle (this may be after any number of journeys if the diagnostic has not been executed) when the subsequent operation of the diagnostic test identifies the same fault, the following occurs:

The temporary diagnostic trouble code (DTC) becomes a permanent code and the TCM transmits this DTC code as the response to OBD diagnostic mode $03 and MIL illumination is requested. The ECM stores a generic transmission failure P code and a data freeze frame. This freeze frame can be requested from the ECM using the scan tool J1979 mode $02 request. On this request the TCM will send a positive response, but the data will equal $00 (i.e. No Parameter Identifiers - PIDs are supported). Upon ignition off this permanent code is stored in the TCM memory and the pending DTC code is erased.

If the subsequent and consecutive 3 complete driving cycles (in which the diagnostic test for the fault is completed) are clear of the fault at ignition off, then the MIL ON request is turned off.
If the subsequent and consecutive 40 warm-up cycles (in which the diagnostic test for the fault is also completed) are clear, then the permanent code (DTC) is erased from the TCM memory.
All permanent and temporary faults can be cleared from the TCM memory using the scan tool J1979 mode $04 request.
All current transmission diagnostic data will be returned to a scan tool J1979 mode $01.
All transmission vehicle information will be returned to a J1979 mode $09 request.