Lexus IS250 IS220d GSE20 ALE20 2AD-FHV ENGINE CONTROL SYSTEM
ECD SYSTEM - DIAGNOSIS SYSTEM
| DESCRIPTION |
When troubleshooting Euro-OBD vehicles, the vehicle must be connected to the intelligent tester. Various data output from the vehicle's Engine Control Module (ECM) can then be read.
The Malfunction Indicator Lamp (MIL) is illuminated when the vehicle's on-board computer detects a malfunction in the computer itself or in drive system components. In addition, the applicable Diagnostic Trouble Codes (DTCs) are recorded in the ECM memory .
If the malfunction does not recur, the MIL stays ON until the engine switch is turned OFF, and then the MIL turns off when the engine switch is turned ON (IG). Be aware that the DTCs remain recorded in the ECM memory.
To check DTCs, connect the intelligent tester to the DLC3 on the vehicle.
| 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 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 .
| 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).
| 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.
| CHECK DLC3 |
The vehicle's ECM uses ISO 9141-2 (Euro-OBD) communication protocol. The terminal arrangement of the DLC3 complies with ISO 15031-03 and matches the ISO 9141-2 format.
| Symbols (Terminal No.) | Terminal Description | Condition | Specified Condition |
| SIL (7) - SG (5) | Bus "+" line | During transmission | Pulse generation |
| CG (4) - Body ground | Chassis ground | Always | Below 1 Ω |
| SG (5) - Body ground | Signal ground | Always | Below 1 Ω |
| BAT (16) - Body ground | Battery positive | Always | 9 to 14 V |
- HINT:
- Connect the cable of the intelligent tester to the DLC3, turn the engine switch ON (IG) and attempt to use the tester. If the display informs that a communication error has occurred, there is a problem either with the vehicle or with the tester.
| INSPECT BATTERY VOLTAGE |
If the voltage is below 11 V, recharge or replace the battery before proceeding.
- Standard voltage:
- 11 to 14 V
| CHECK MIL |
The MIL illuminates when the engine switch is turned ON (IG) and the engine is not running.
- HINT:
- If the MIL is not illuminated, check the MIL circuit .
When the engine is started, the MIL should turn OFF. If the lamp remains ON, the diagnosis system has detected a malfunction or abnormality in the ECD system.