On-Board Diagnostic System Description
On-Board Diagnostic System DescriptionECM in this vehicle has the following functions in compliance with OBD-II regulations.
^ When the ignition switch is turned ON with the engine at a stop, malfunction indicator lamp (MIL) (1) turns ON to check the MIL (1) and its circuit.
^ When ECM detects a malfunction which gives an adverse effect to vehicle emission while the engine is running, it makes MIL in the meter cluster of the instrument panel turn ON or flash (flashing only when detecting a misfire which can cause damage to the catalyst) 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.)
^ As a condition for detecting a malfunction in some areas in the system being monitored by ECM and turning on MIL due to that malfunction, 2 driving cycle detection logic is adopted to prevent erroneous detection.
^ When a malfunction is detected, engine and driving conditions are stored in ECM memory as freeze frame data. (For the details, refer to description on Freeze Frame Data.)
^ It is possible to communicate via DLC (data link connector) (3) by using not only SUZUKI scan tool (SUZUKI-SDT) (2) but also CAN communication OBD-II generic scan tool which are in compliance with SAE J1978. (Diagnostic information can be accessed by using a scan tool.)
Warm-Up Cycle
A warm-up cycle means sufficient vehicle operation such that the coolant temperature has risen by at least 22°C (40°F) from engine starting and reaches a minimum temperature of 70°C.
Driving Cycle
A "Driving Cycle" consists of engine startup, and engine shutoff.
2 Driving Cycle Detection Logic
The malfunction detected in the first driving cycle is stored in ECM memory (in the form of pending DTC and freeze frame data) but the MIL 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.
Freeze Frame Data
ECM stores the engine and driving conditions (in the form of data as shown) 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.
Freeze Frame Data (for Example):
Priority of freeze frame data
ECM has 4 frames where the freeze frame data can be stored. The first frame stores the freeze frame data of the malfunction which was detected first. However, the freeze frame data stored this frame is updated according to the priority described below. (If malfunction as described in the upper square "1" below is detected while the freeze frame data in the lower square "2" has been stored, the freeze frame data "2" will be updated by the freeze frame data "1".)
In the 2nd through the 4th frames, the freeze frame data of each malfunction is stored in the order as the malfunction is detected. These data are not updated. Shown in the table below are examples of how freeze frame data are stored when two or more malfunctions are detected.
Freeze frame data clearance
The freeze frame data is cleared at the same time as clearance of DTC or Pending of DTC.
DLC (Data Link Connector)
DLC (1) is in compliance with SAE J1962 in its installation position, the shape of connector and pin assignment.
OBD-II CAN Hi line (6) and Low line (3) (CAN line of ISO 15765-4) are used for SUZUKI scan tool (SUZUKI-SDT) (7) or CAN communication OBD-II generic scan tool to communicate with ECM (included in immobilizer) and TCM.
