On-Board Diagnostic (OBD) System Description
On-Board Diagnostic (OBD) System Description
ECM in this vehicle has the following functions.
- When the ignition switch is turned to ON position with the engine stopped, malfunction indicator lamp (MIL) (1) turns on in order to check the MIL (1) and its circuit.
- When ECM detects a malfunction which gives an adverse effect to vehicle emission more than specified driving cycle (D/C), it turns on or flashes MIL in the combination meter (flashing only when detecting a misfire which can cause damage to the catalyst) and stores the diagnostic trouble code (DTC) in its memory.
(If it detects normal condition for continuously 3 driving cycles after detecting a malfunction, it turns off MIL although DTC stored in its memory is remained as a history DTC.)
- For some malfunctions, ECM adopts the 2 D/C detecting logic to prevent erroneous detection. With this logic, MIL is turned on when the malfunction is detected in 2 consecutive driving cycles.
- Malfunctions detected by ECM 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 (EVAP Leak Check Model).)
- When a malfunction is detected, engine and driving conditions at that moment are stored in ECM memory as freeze frame data.
For details, refer to description on Freeze Frame Data.
- It is possible to communicate ECM via data link connector (DLC) (3) not only by SUZUKI scan tool (SUZUKI-SDT) (2) but also by CAN communication OBD generic scan tool.
Warm-Up Cycle
A warm-up cycle means the duration from the engine start until the coolant temperature has risen by at least 22 °C (40 °F) exceeding the minimum temperature of 71 °C (160 °F).
Driving Cycle (D/C)
A "Driving Cycle" is a duration from an engine startup to the following 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 turn on at this time. It turns on at the second detection of the same malfunction in the next driving cycle.
Pending DTC
Pending DTC means a DTC detected and stored temporarily at the first driving cycle of the 2 driving cycle detection logic.
Permanent DTC (EVAP Leak Check Model)
In accordance with SAE J1979, ECM 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 ECM.
Only when does ECM 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
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".
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 of their detection. Utilizing this function, it is possible to know the order of detection of these malfunctions. This is helpful when rechecking or diagnosing a trouble.
For details of freeze frame data that can be read from ECM, refer to table below.
NOTE:
- For freeze flame data with asterisk (*), it indicates the ratio between power supply voltage and output voltage of related sensor.
When power supply voltage is 5.0 V and output voltage is 4.0 V, freeze frame data is displayed the following.
- For systems where the output is proportional to the input voltage, it displays 80% (= the percent of maximum input reference voltage).
- For systems where the output is inversely proportional to the input voltage, it displays 20% (=100% minus the percent of maximum input reference voltage).
- For relative TP with asterisks (**) in above table, it indicates by formula ((output voltage - output voltage at closed throttle position) / power supply voltage).
When power supply voltage is 5.0 V and output voltage at closed throttle position is 1.0 V, freeze frame data is displayed the following.
- At closed throttle position (output voltage = 1.0 V), it displays 0%.
- At wide open throttle position (output voltage = 4.0 V), it displays 60%. However, for systems where the output is inversely proportional to the input voltage, it displays 100% minus above-mentioned formula.
Freeze flame 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 in 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 of detection. These data are not updated.
Shown in the table below are examples of how freeze frame data are stored when two or more DTCs are detected.
-: No freeze frame data
Freeze frame data clearance
The freeze frame data is cleared at the same time as clearance of DTC.
System Readiness Test
The system readiness test is to check if the on-board diagnosis of each system related to exhaust emission has been completed or not using a scan tool (Suzuki SDT or CAN communication OBD generic scan tool). When the conditions established for each system are met, ECM performs an on-board diagnosis of corresponding system and changes the status of system readiness test from "Incomplete" to "Complete".
When "Complete" status is displayed, it is maintained until the "DTC clearance" is performed using scan tool.
NOTE:
- The status of system readiness test may be changed as "incomplete" when performing the following services.
- Disconnection of battery negative cable
- Disconnection of ECM connectors
- Removal of ground cable for ECM
- Disconnection of "ECM" fuse
- By utilizing this system readiness test, it is possible to confirm that all DTC confirmation procedure for each system has been completed or incompleted. For all DTCs related to each system, refer to the table below.
- The system readiness test is NOT the result ("Normal" or "Abnormal") of the on-board diagnosis but the result ("Complete" or "Incomplete") of the on-board diagnosis.
Monitoring item of system readiness test table
NOTE:
*1: For item with asterisk 1 (*1) in the table below, it is applicable for EVAP-Leak-Check Model.
