Electric Throttle Control (ETC) System Check
Electric Throttle Control (ETC) System CheckCircuit Description
- The Engine Control Module (ECM) controls engine speed by adjusting the position of the throttle control valve (DC motor). The throttle motor is a DC motor driven by one coil. The ECM applies current to the DC motor coil in PWM (%) to adjust the throttle valve into a passage in the throttle body to allow air flow. This method allows highly accurate control of engine speed and quick response to changes in engine load.
- The acceleration position (AP1) sensor circuit provides a voltage signal relative to acceleration pedal angle.
The acceleration pedal angle will vary about 0.65 V at idle position to about 4.35 V at wide open throttle (WOT).
APS signal is used to determine which DC motor will adjust throttle position.
After the APS signal has been processed by the ECM, it will command DC motor to allow movement of throttle position.
Diagnostic Aids
- An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside the insulation. Check for poor connections or a damaged harness. Inspect the ECM harness and connector for improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness.
- Throttle body - Check for objects blocking the DC motor or throttle bore, excessive deposits in the ETC passage and on the valve spring, and excessive deposits in the throttle bore and on the throttle valve plate.
- Acceleration pedal - Check for objects blocking the AP sensor or pedal arm with spring, excessive deposits in the acceleration pedal arm and on the acceleration pedal and lacking the pedal stopper rubber.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:
2. Visually/physically inspect for the following throttle valve conditions.
3. Visually/physically inspect for the following acceleration pedal conditions.
5. Check the following circuits for throttle valve and DC motor. Check the following TP sensor resistance and DC motor.
6. Check the following circuits for acceleration pedal. Check the following AP sensor resistance.
7. Following DTC: Error for ETC system.
Step 1:
Steps 2 - 3:
Steps 4 - 7:
