Theory Of Operation

WARNING: This page is about a different car, the 2016 RAM 1500. However, it is still accessible from the selected car via links, so may be relevant.

The Electronic Throttle Control (ETC) Motor is controlled using an H-Bridge circuit inside the Powertrain Control Module (PCM). An H-Bridge is an electronic circuit that enables a voltage to be applied across a load in either direction. The H-Bridge arrangement is generally used to reverse the polarity/direction of the DC motor which allows the DC motor to run forward and backwards. The DC motor located in the Throttle Body drives the throttle blade. In order to decrease engine speed, along with spark and fuel delivery changes, the PCM commands the throttle blade closed reducing air flow into the engine and the engine speed decreases. In order to increase engine speed, the PCM commands the throttle blade open, increasing air flow and engine speed.

See the figure below for a general configuration and operation of an H-Bridge:

Fig 1: General Configuration And Operation Of An H-Bridge

Courtesy of CHRYSLER GROUP, LLC

An H-Bridge circuit is built with four solid-state switches. When the switches S1 and S4 (according to the first figure) are closed (and S2 and S3 are open) a positive voltage will be applied across the motor. Opening S1 and S4 switches and closing S2 and S3 switches, will reverse the voltage, allowing the motor to reverse operation.

DIAGNOSTICS: The PCM performs diagnostics on the DC Motor and circuits. If the PCM detects that the current draw or Pulse Width Modulation (PWM) to the DC Motor is too high or low for a calibrated amount of time, then the PCM determines that the motor or circuitry is faulted and not operating properly.

NOTE: The PCM can detect a circuit high or circuit low fault during operation of the component, whereas open circuit detection can only occur when the component is not being commanded on. If an open occurs in the component or circuits during operation, the PCM will normally detect the failure during the performance diagnostic for the system that component is being used to control.