Freestar V6-4.2L VIN 2 (2004)
Electronic Throttle Control Module: Description and Operation
TORQUE BASED ELECTRONIC THROTTLE CONTROL (ETC)
The Generation II (Gen II) Torque Based Electronic Throttle Control (ETC) is a hardware and software strategy that delivers a transmission output
shaft torque (via throttle angle) based on driver demand (pedal position). It utilizes an electronic throttle body, the PCM and a accelerator pedal
assembly to control throttle opening and engine torque. The ETC system basically replaces the standard cable operated accelerator pedal, idle air
control (IAC) motor, 3-wire throttle position sensor (TPS) and mechanical throttle body
Background "Why Torque Based ETC"
Torque based ETC enables aggressive automatic transmission shift schedules (earlier upshifts and later downshifts). This is possible by adjusting the
throttle angle to achieve the same wheel torque during shifts, and by calculating this desired torque, the system prevents engine lugging (low RPM and
low manifold vacuum) while still delivering the performance and torque requested by the driver.
It also enables many fuel economy/emission improvement technologies such as:
VCT (deliver same torque during transitions)
Hybrid Electric Vehicle (HEV)
Torque based ETC also results is a less intrusive vehicle and engine speed limiting, along with smoother traction control.
Other generic benefits of ETC are:
Eliminate cruise control actuators
Eliminate Idle Air Control (IAC) Bypass actuator
Better airflow range
Packaging (no cable)
More responsive powertrain at altitude and improved shift quality
It should be noted that the ETC system includes a wrench light on the instrument cluster that illuminates when a fault is detected. Faults are also
accompanied by DTCS and the "Check Engine Soon" light.
Electronic Throttle Body (ETB)
The Gen II electronic throttle body (Figure 133) has the following characteristics
1. The DC motor is driven by the PCM (requires two wires). The gear ratio from the motor to the throttle plate shaft is 17:1.
2. There are two designs; parallel and in-series. The parallel design has the motor under the bore parallel to the plate shaft. The motor housing is
integrated into the main housing (in general this is more difficult to package). The in-series design has a separate motor housing that protrudes out
and offers more packaging flexibility.
3. Two springs are used: one is used to close the throttle (main spring) and the other is in a plunger assembly that results in a default angle with no
power applied. This is for limp home reasons (force of plunger spring is 2 times stronger than the main spring). Default angle is usually set to
result in a top vehicle speed of 30 MPH (48 Km). Typically this throttle angle is 7 to 8 degrees from the hard-stop angle.
4. The closed throttle plate hard stop is used to avoid the throttle from binding in the bore (approximately 0.75 degree). This hard stop setting is
non-adjustable and is set to result in less airflow than the minimum engine airflow required at idle.
5. Unlike cable type throttle bodies, the intent for the ETB is not to have a hole in the throttle plate or to use plate sealant. The hole is not required in
the ETB because the required idle airflow is provided by the plate angle in the throttle body assembly. This plate angle controls idle and idle
quality and eliminates the need for IAC bypass actuator.
6. The system has two throttle position sensors. Redundant throttle position signals are required for monitor reasons. TP1 has a negative slope
(increasing angle, decreasing voltage) and TP2 has a positive slope (increasing angle, increasing voltage). During normal operation the negative
sloped TP sensor (TP1) is used by the control strategy as the indication of throttle position. The TP sensor assembly requires four wires.
5 V Reference Voltage
Signal Return (ground)
TP1 voltage with negative voltage slope (5-0)
TP2 voltage with positive voltage slope (0-5)
Accelerator Pedal Position Sensors (APPS)
The ETC strategy uses pedal position sensors as an input to determine the driver demand.
1. There are three pedal position sensors required for system monitoring. APP1 has a negative slope (increasing angle, decreasing voltage) and APP2
& APP3 both have a positive slope (increasing angle, increasing voltage). During normal operation APP1 is used as the indication of pedal
position by the strategy.
2. There are two VREF wires, two signal return wires and three signal wires (total of seven wires and pins) between the PCM and APPS assembly.
2-5 V Reference Voltage
2- Signal Return (ground)
APP1 voltage with negative voltage slope (5-0)
APP2 voltage with positive voltage slope (0-5)
APP3 voltage with positive voltage slope (0-5)
3. The pedal position signal is converted to pedal travel degrees (rotary angle) by the PCM. The software then converts these degrees to counts,