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 accelerator pedal position sensor is mounted on the accelerator pedal bracket and it has 2 sensors to detect the accelerator position and a malfunction of the accelerator position sensor. Voltage applied to pedal terminals VPA and VPA2 of ECM changes between 0-5 volts in proportion to opening angle of the accelerator pedal. VPA is a signal to indicate the actual accelerator pedal opening angle which is used for the engine control, and VPA2 is a signal to indicate the information about the opening angle which is used for detecting a malfunction. ECM judges the current opening angle of the accelerator pedal from these signals input from terminals VPA and VPA2. ECM controls throttle motor based on these signals. If DTCs are stored, 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
- Open or short in accelerator pedal position sensor circuit.
- Faulty accelerator pedal position sensor.
- Faulty ECM.
Diagnostic Aids
Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.