System Operation

General Description
The automatic transmission control system in this vehicle is controlled by TCM. TCM has an On-Board Diagnostic system which detects a malfunction in this system and abnormality of those parts that influence the engine exhaust emission. When diagnosing automatic transmission troubles, be sure to have full understanding of the outline of "On-Board Diagnostic System Description:" and each item in "Precautions in Diagnosing Trouble for Automatic Transmission:" and execute diagnosis according to "A/T System Check:".

On-Board Diagnostic System
For automatic transmission control system, TCM has the following functions.
^ When the ignition switch is turned ON with no malfunction in A/T control system detected, the "O/D OFF" lamp lights for about 2 seconds after the ignition switch is turned ON and then goes OFF for the bulb check. If the O/D cut switch is ON at this time, however, "O/D OFF" lamp remains ON to let driver know that gear is not shifted to overdrive gear (4th gear).





^ When a malfunction in A/T control system (and/or a malfunction which gives an adverse effect to vehicle emission) is detected, it flashes "O/D OFF" lamp, stores the malfunction DTC and at the same time transmits DTC of that malfunction to ECM. (Based on this signal, ECM turns ON malfunction indicator lamp (MIL, "CHECK ENGINE" lamp) and stores DTC/freeze frame data then in its memory.)
^ If no malfunction is detected in the next driving cycle after detecting above malfunction, TCM does not flash "O/D OFF" lamp and does not transmit DTC of that malfunction to ECM, however, DTC stored in TCM memory will remain. If ECM receives no DTC of malfunction for 3 driving cycles continuously, it turns OFF MIL although DTC stored in ECM memory will also remain.

Freezed Frame Data
ECM 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, where air/fuel mixture was lean or rich) when a malfunction was detected by checking the freeze frame data. Also, ECM has a function to store each freeze frame data for three different malfunctions in the order as the malfunction is detected. Utilizing this function, it is possible to know the order of malfunctions that have been detected. Its use is helpful when rechecking or diagnosing a trouble.

2 Driving Cycle Detection Logic
When a malfunction is detected during the initial driving cycle, it is stored in TCM memory and at the same time TCM transmits a data to inform that a malfunction occurred to ECM. At this time, ECM stores a corresponding pending DTC in its memory.
(Neither lighting of MIL nor flashing of "O/D OFF" light takes place then.)
If the same malfunction is also detected in the next driving cycle, TCM flashes "O/D OFF" light and ECM lights MIL when it receives a data informing occurrence of a malfunction from TCM.

Precautions in Diagnosing Trouble for Automatic Transmission
^ Don't disconnect couplers from ECM, battery cable from battery, ECM ground wire harness from engine or main fuse before checking the diagnosis information (DTC, freeze frame data, etc.) stored in ECM memory. Such disconnection will clear memorized information in ECM memory.
^ Using SUZUKI scan tool or OBD-II generic scan tool, the A/T diagnostic information stored in ECM memory can be checked and cleared as well. Before its use, be sure to read Operator's (instruction) Manual supplied with it carefully to have good understanding of its functions and usage.
^ DTC stored in TCM can not be cleared by using ECM (OBD-II) application of SUZUKI scan tool in Mass storage cartridge or OBD-II generic scan tool. Be sure to follow DTC clearance procedure, refer to "DTC Clearance:" when clearing it.
^ Priorities for diagnosing troubles
If two or more DTCs are stored, proceed to DTC flow of the DTC which was detected earliest in the order and follow the instruction in that DTC flow.
If no instructions are given, troubleshoot diagnostic trouble codes according to the following priorities.
- DTCs other than DTC P0171/P0172 (Fuel system too lean/too rich), DTC P0300/P0301/P0302/P0303/P0304 (Misfire detected) and DTC P0401/P0402 (EGR flow malfunction)
- DTC P0171/P0172 (Fuel system too lean/too rich) and DTC P0401/P0402 (EGR flow malfunction)
- DTC P0300/P0301/P0302/P0303/P0304 (Misfire detected)
^ Be sure to read "Precautions for Electrical Circuit Service:" before inspection and observe what is written there.
^ TCM and/or ECM replacement
When substituting a known-good TCM and/or ECM, check for the following conditions. Neglecting this check may result in damage to a good TCM and/or ECM.
- All relays and actuators have resistance of specified value.
- MAF sensor, TP sensor and fuel tank pressure sensor (if equipped) are in good condition. Also, the power circuit of these sensors is not shorted to the ground.

Precautions for Disassembly and Assembly for Automatic Transmission

CAUTION:
^ Thoroughly clean transmission exterior before over-hauling it.
^ Keep working table, tools and hands clean while overhauling.
^ Use special care to handle aluminum parts so as not to damage them.
^ Do not expose removed parts to dust. Keep them clean always.