Diagnosis System
- When troubleshooting OBD II (On-Board Diagnostics) vehicles, the Techstream (complying with SAE J1987) must be connected to the DLC3 (Data Link Connector 3) of the vehicle. Various data in the vehicle's ECM (Engine Control Module) can be then read.
- OBD II regulations require that the vehicle's on-board computer illuminates the MIL (Malfunction Indicator Lamp) on the instrument panel when the computer detects a malfunction in:
- The emission control system and components.
- The powertrain control components (which affect vehicle emissions).
- The computer itself.
- In addition, the applicable DTCs prescribed by SAE J2012 are stored in the ECM memory. If the malfunction does not recur in 3 consecutive trips, the MIL turns off automatically but the DTCs remain stored in the ECM memory.
- To check the DTCs, connect the Techstream to the DLC3. The Techstream displays output DTCs, freeze frame data, and a variety of engine data. The DTCs and freeze frame data can be cleared with the Techstream. In order to enhance OBD function on vehicles and develop the Off-Board diagnosis system, Controller Area Network (CAN) communication is used in this system. CAN is a network which uses a pair of data transmission lines spanning multiple computers and sensors. It allows for high speed communications between the systems and simplification of the wire harness connections.
- NORMAL MODE AND CHECK MODE
The diagnosis system operates in normal mode during normal vehicle use. In normal mode, 2 trip detection logic is used to ensure accurate detection of malfunctions. Check mode is also available as an option for technicians. In check mode, 1 trip detection logic is used for duplicating malfunction symptoms and increasing the system's ability to detect malfunctions, including intermittent problems (the Techstream only).
- 2 TRIP DETECTION LOGIC
- When a malfunction is first detected, the malfunction is temporarily stored in the ECM memory (1st trip). If the same malfunction is detected during the subsequent driving cycle, the MIL is illuminated (2nd trip).
- FREEZE FRAME DATA
- The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air-fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
- DLC3 (Data Link Connector 3)
- Check the DLC3. Refer to GENERAL INFORMATION .
- BATTERY VOLTAGE
Standard Voltage
11 to 14 V
- If voltage is below 11 V, replace or recharge the battery before proceeding to the next step.
- MIL (Malfunction Indicator Lamp)
- The MIL illuminates when the ignition switch is turned to ON (the engine is not running).
- The MIL should turn off when the engine is started. If the MIL remains illuminated, the diagnosis system has detected a malfunction or abnormality in the system.
HINT:
If the MIL does not illuminate when the ignition switch is turned to ON, check the MIL circuit. Refer to MIL Circuit .
- ALL READINESS
HINT:
- With "All Readiness", you can check whether or not the DTC judgment has been completed by using the Techstream.
- You should check "All Readiness" after duplicating malfunction symptoms or for validation after finishing repairs.
- Connect the Techstream to the DLC3.
- Turn the ignition switch to ON.
- Turn the Techstream on.
- Clear the DTCs. Refer to DTC CHECK / CLEAR .
- Perform the DTC judgment driving pattern to run the DTC judgment.
- Enter the following menus: Powertrain / Engine / Utility / All Readiness.
- Input the DTCs to be confirmed.
- Check the DTC judgment result.
Techstream Display Description NORMAL - DTC judgment completed
- System normal
ABNORMAL - DTC judgment completed
- System abnormal
INCOMPLETE - DTC judgment not completed
- Perform the driving pattern after confirming the DTC enabling conditions
N/A - Unable to perform DTC judgment
- Number of DTCs which do not fulfill DTC preconditions has reached ECU's memory limit