On-Board Diagnostic System Description

On-Board Diagnostic System Description

For automatic transmission control system, TCM has the following functions. Refer to Inspection of TCM and Its Circuits Inspection of TCM and Its Circuits.

- When the ignition switch is turned ON with the engine at a stop, malfunction indicator lamp (MIL) (1) turns ON to check the bulb of the MIL.
- When TCM detects a malfunction in A/T control system (and/or a malfunction which gives an adverse effect to vehicle emission) while the engine is running, TCM requires ECM to make the MIL in the meter cluster of the instrument panel turn ON. TCM stores the malfunction area (DTC according to SAE J2012) in TCM memory.
(If it detects that continuously 3 driving cycles are normal after detecting a malfunction, however, it makes MIL turn OFF although DTC stored in its memory will remain.)
- Malfunctions detected by TCM are stored in its memory as pending DTC, confirmed DTC (current and history) and permanent DTC. The permanent DTC, among others, will be stored in the memory that cannot be manually erased. (For the details, refer to description on Permanent DTC.)
- It is possible to communicate through DLC (2) by using not only SUZUKI scan tool but also OBD-II generic scan tool which are in compliance with SAEJ1978. (Diagnostic information can be checked and erased by using a scan tool.)
Special Tool

(A): SUZUKI scan tool (SUZUKI-SDT)





2 Driving Cycle Detection Logic

The malfunction detected in the first driving cycle is stored in TCM memory (in the form of pending DTC and freeze frame data) but the malfunction indicator lamp does not light at this time. It lights up at the second detection of same malfunction also in the next driving cycle.

Pending DTC

Pending DTC means a DTC detected and stored temporarily at 1 driving cycle of the DTC which is detected in the 2 driving cycle detection logic.

Permanent DTC

In accordance with SAE J1979, TCM stores DTCs that adversely affect vehicle emission (i.e. DTCs with MIL turning on) in a non-volatile RAM (NVRAM) separately from that for pending and confirmed DTCs. This DTC is called a permanent DTC.

Unlike pending and confirmed DTCs, the permanent DTC will not be cleared even when executing the clear command of scan tool or when shutting off the power to TCM. Only when does TCM detect no malfunction in the trouble area of the stored permanent DTC with the condition determined normal, the permanent DTC will be cleared. (For permanent DTC clearance, refer to DTC Clearance DTC Clearance.)

The maximum of four earliest detections of the permanent DTCs will be stored in memory. The DTCs are cleared in the order of completing determination as normal.

Freeze Frame Data

TCM stores the engine and driving conditions at the moment of the detection of a malfunction in its memory. This data is called "Freeze frame data".

Therefore, it is possible to know engine and driving conditions (e.g., whether the engine was warm or not, where the vehicle was running or stopped) when a malfunction was detected by checking the freeze frame data.