Note. For information on engine immobilizer system, see COMPUTERIZED ENGINE CONTROLS in THEORY & OPERATION article.
| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES - LEXUS article. |
Circuit Description
The Electric Throttle Control System (ETCS) is composed of the throttle motor to operate the throttle valve, the throttle position sensor to detect the opening angle of the throttle valve, the accelerator pedal position sensor to detect the accelerator pedal position, the ECM to control the ETCS, and the one valve type throttle body. The ECM controls the throttle motor to make the throttle valve opening angle properly in response to the driving condition. The throttle position sensor mounted on the throttle body detects the opening angle of the throttle valve, and it provides feedback to the ECM to control the throttle motor. If the ETCS has a malfunction, the ECM shuts down the power for the throttle motor, and the throttle valve is fully closed by the return spring. Throttle valve is locked at a certain opening angle. Electronically controlled throttle operation is cancelled until the system returns to normal and the ignition switch is turned OFF. Possible causes are
- ETCS.
- Faulty ECM.
Diagnostic Aids
Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.