Description of On-Board Diagnostics
GENERAL DESCRIPTIONThe automatic transmission control system in this vehicle is controlled by the Powertrain (Engine) Control Module (PCM). PCM 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" and execute diagnosis according to "AUTOMATIC TRANSMISSION DIAGNOSTIC FLOW TABLE".
ON-BOARD DIAGNOSTIC SYSTEM
For automatic transmission control system, the Powertrain (Engine) Control Module (PCM) has the following functions.
- When the ignition switch is turned ON with the engine at a stop, MIL turns ON to check the bulb of the Malfunction Indicator Lamp (MIL).
- When PCM 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, it makes the MIL in the meter cluster of the instrument panel turn ON and stores the malfunction area (DTC according to SAE J2012) in its 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.)
- It is possible to communicate through DLC by using not only SUZUKI scan tool (Tech-1) but also OBD-II generic scan tool which are in compliance with SAEJ1978. (Diagnostic information can be accessed by using a scan tool.)
PRECAUTION IN DIAGNOSING TROUBLE
- Don't disconnect couplers from Powertrain (Engine) Control Module (PCM), battery cable from battery, PCM ground wire harness from engine or main fuse before checking the diagnosis information (DTC, freeze frame data, etc.) stored in PCM memory. Such disconnection will clear memorized information in PCM memory.
- Using SUZUKI scan tool (Tech-1) or OBD-II generic scan tool, the diagnostic information stored in PCM 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.
PRIORITIES FOR DIAGNOSING TROUBLES
If two or more Diagnostic Trouble Codes (DTCs) are stored, proceed to the flow table of the DTC which was detected earliest in the order and follow the instruction in that table.
If no instructions are given, troubleshoot DTCs according to the following priorities.
1. DTCs other than DTC P0171/PO172 (Fuel system too lean/too rich), DTC P0300/PO301/PO302/PO303/PO304 (Misfire detected) and DTC P0400 (EGR flow malfunction)
2. DTC P0171/PO172 (Fuel system too lean/too rich) and DTC P0400 (EGR flow malfunction)
3. DTC P0300/PO301/PO302/PO303/PO304 (Misfire detected)
PCM REPLACEMENT
When substituting a known-good PCM, check for the following conditions. Neglecting this check may result in damage to a good PCM.
- All relays and actuators have resistance of specified value.
- MAP sensor, Throttle Position (TP) sensor and fuel tank pressure sensor are in good condition. Also, the power circuit of these sensors is not shorted to the ground.