Diagnosis System

2AZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: DIAGNOSIS SYSTEM

DIAGNOSIS SYSTEM

1. DESCRIPTION
- 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 illuminate the MIL (Malfunction Indicator Lamp) on the instrument panel when the computer detects a malfunction in:





1. The emission control system components
2. The powertrain control components (which affect vehicle emissions)
3. The computer itself

- In addition, if the applicable DTCs (Diagnostic Trouble Codes) prescribed by SAE J2012 are not recorded on 3 consecutive trips, the MIL turns off automatically but the DTCs remain recorded in the ECM memory.
- To check DTCs, connect the Techstream to the DLC3. The Techstream displays DTCs, freeze frame data, and a variety of the engine data. The DTCs and freeze frame data can be erased with the Techstream DTC Check / Clear.
In order to enhance OBD function on vehicles and develop the Off-Board diagnosis system, CAN (Controller Area Network) communication is introduced in this system. It minimizes the gap between technician skills and vehicle technology. CAN is a network, which uses a pair of data transmission lines, spanning multiple computers and sensors. It allows high speed communication between the systems and simplifies the wire harness connection.

2. 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 simulating malfunction symptoms and increasing the system's ability to detect malfunctions, including intermittent problems (Techstream only) Check Mode Procedure.

3. 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 next subsequent drive cycle, the MIL is illuminated (2nd trip).

4. 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.

5. DLC3 (Data link Connector 3)
- The vehicle's ECM uses ISO 15765-4 for communication protocol. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 15765-4 format.









HINT: The DLC3 is the interface prepared for reading various data from the vehicle's ECM. After connecting the cable of the Techstream, turn the ignition switch to the ON position and turn the Techstream on. If a communication failure message is displayed on the Techstream, a problem exists in either the vehicle or Techstream. In order to identify the location of the problem, connect the Techstream to another vehicle.

If communication is normal: Inspect the DLC3 on the original vehicle.
If communication is still not possible: The problem is probably in the Techstream itself. Consult the Service Department listed in the instruction manual.

6. BATTERY VOLTAGE
Battery voltage:
11 to 14 V
- If the voltage is below 11 V, recharge or replace the battery before proceeding to the next step.

7. Malfunction Indicator Lamp (MIL)
(a) The MIL is illuminated when the ignition switch is first turned to the ON position (the engine is not running).
(b) 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 is not illuminated when the ignition switch is first turned to the ON position, check the MIL circuit MIL Circuit.

8. 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 simulating malfunction symptoms or for validation after finishing repairs.

(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to the ON position.
(c) Turn the Techstream ON.
(d) Clear the DTCs DTC Check / Clear.
(e) Perform the DTC judgment driving pattern to run the DTC judgment.
(f) Select the following menu items: Powertrain / Engine and ECT / Utility / All Readiness.
(g) Input the DTCs to be confirmed.
(h) Check the DTC judgment result.

Techstream