Diagnosis System

AA80E AUTOMATIC TRANSMISSION: AUTOMATIC TRANSMISSION SYSTEM: DIAGNOSIS SYSTEM

1. DESCRIPTION
(a) When troubleshooting On-Board Diagnostic (OBD II) vehicles, the vehicle must be connected to the OBD II scan tool (complying with SAE J1987). Various data output from the vehicle's TCM can then be read.






(b) OBD II regulations require that the vehicle's on-board computer illuminate the Malfunction Indicator Lamp (MIL) 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
In addition, the applicable Diagnostic Trouble Codes (DTCs) prescribed by SAE J2012 are recorded in the TCM memory.
When the malfunction does not reoccur, the MIL stays illuminated until the engine switch is turned off, and the MIL turns off when the engine is started. However, the DTCs remain recorded in the TCM memory.

(c) To check DTCs, connect the Techstream to the Data Link Connector 3 (DLC3) of the vehicle. The Techstream displays DTCs, freeze frame data and a variety of engine data.
The DTCs and freeze frame data can be erased with the Techstream DTC Check / Clear.
2. NORMAL MODE AND CHECK MODE
(a) 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 to technicians as an option. In check mode, "1 trip detection logic" is used for simulating malfunction symptoms and increasing the system's ability to detect malfunctions, including intermittent malfunctions.
3. 2 TRIP DETECTION LOGIC
(a) When a malfunction is first detected, the malfunction is temporarily stored in the TCM memory (1st trip). If the same malfunction is detected during the next drive cycle, the MIL is illuminated (2nd trip).
4. FREEZE FRAME DATA
(a) Freeze frame data records the engine conditions (fuel system, calculated load, engine coolant temperature, fuel trim, engine speed, vehicle speed, etc.) when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.






(b) The Techstream records freeze frame data in 5 different instances: 1) 3 times before the DTC is set, 2) once when the DTC is set, and 3) once after the DTC is set. These data can be used to simulate the vehicle's condition around the time when the malfunction occurred. The data may help in finding the cause of the malfunction, or in judging if the DTC is being caused by a temporary malfunction or not.

5. CHECK DATA LINK CONNECTOR 3 (DLC3)
- The TCM uses ISO 15765-4 for communication. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 15765-4 format.









NOTICE:
*: Before measuring the resistance, leave the vehicle as is for at least 1 minute and do not operate the engine switch, any other switches or the doors.
HINT:
The DLC3 is the interface prepared for reading various data from the vehicle's TCM. After connecting the cable of the Techstream, turn the engine switch on (IG) and turn the Techstream on. If a communication failure message is displayed on the Techstream screen, a problem exists in either the vehicle or the 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. CHECK MIL
(a) Check that the MIL illuminates when turning the engine switch on (IG).
If the MIL does not illuminate, there is a problem in the MIL circuit MIL Circuit.
(b) When the engine is started, the MIL should turn off.