Diagnosis System

U341E AUTOMATIC TRANSAXLE: AUTOMATIC TRANSAXLE 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 ECM can then be read.

(b) OBD II regulations require that the vehicle's on-board computer illuminates 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 ECM 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 ECM memory.

(c) To check DTCs, connect a Techstream to the Data Link Connector 3 (DLC3) of the vehicle. The Techstream displays DTCs, the 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.

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 ECM 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 running or stopped, 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 ECM records engine conditions in the form of freeze frame data every 0.5 seconds. Using a Techstream, five separate sets of freeze frame data, including the data values at the time when the DTC was set, can be checked.

* 3 data sets before the DTC was set

* 1 data set when the DTC was set

* 1 data set after the DTC was set

(b) These data sets can be used to simulate the condition of the vehicle around the time the occurrence of the malfunction. The data may assist in identifying of the cause of the malfunction, and in judging whether it was temporary or not.





5. BATTERY VOLTAGE

Standard voltage:

11 to 14 V

* If voltage is below 11 V, replace or recharge the battery before proceeding.

6. DATA LINK CONNECTOR 3 (DLC3)

(a) Check the DLC3 General Information.

7. CHECK MIL

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

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.