Diagnosis System

U760E AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSAXLE SYSTEM: DIAGNOSIS SYSTEM

1. DESCRIPTION

* 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.

* 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:





* The emission control system/components

* The powertrain control components which affect vehicle emissions

* 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 ignition switch is turned off, and the MIL turns off when the engine is started. However, the DTCs remain recorded in the TCM memory.

* 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 cleared with the Techstream Reading and Clearing Diagnostic Trouble Codes.

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 to increase the system's ability to detect malfunctions, including intermittent malfunctions, when simulating malfunction symptoms.

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 data, 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 TCM records freeze frame data at 5 different points: 1) 3 times before the DTC is stored, 2) once when the DTC is stored, and 3) once after the DTC is stored. These data can be used to simulate the vehicle condition from around the time when the malfunction occurred. The data may be helpful in finding the cause of the malfunction, or determining if the DTC is being caused by a temporary malfunction or not.





5. CHECK DATA LINK CONNECTOR 3 (DLC3) General Information

6. CHECK MIL

(a) Check that the MIL illuminates when the ignition switch is turned to ON.

If the MIL does not illuminate, there is a problem in the MIL circuit MIL Circuit.

(b) Check that when the engine is started, the MIL goes off.