Expedition 4WD V8-5.4L VIN 5 (2006)
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Electronic Throttle Control Module: Description and Operation
TORQUE BASED ELECTRONIC THROTTLE CONTROL (ETC)
Overview
The torque based ETC is a hardware and software strategy that delivers an engine output torque (via throttle angle) based on driver demand (pedal
position). It uses an electronic throttle body, the powertrain control module (PCM), and an accelerator pedal assembly to control the throttle opening
and engine torque. The ETC system replaces the standard cable operated accelerator pedal, idle air control (IAC) valve, 3-wire throttle position sensor
(TPS), and mechanical throttle body.
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 variable camshaft timing (VCT) (deliver same torque during transitions).
Torque based ETC also results in less intrusive vehicle and engine speed limiting, along with smoother traction control.
Other benefits of ETC are:
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eliminate cruise control actuators
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eliminate idle air control (IAC) valve
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better airflow range
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packaging (no cable)
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more responsive powertrain at altitude and improved shift quality
It should be noted that the ETC system illuminates a powertrain malfunction indicator (wrench) on the instrument cluster when a concern is present.
Concerns are accompanied by diagnostic trouble codes (DTCs) and may also illuminate the malfunction indicator lamp (MIL).
Electronic Throttle Body (ETB)
The ETB has the following characteristics:
1. The throttle actuator control (TAC) motor is a DC motor controlled by the PCM (requires 2-wires). The gear ratio from the motor to the throttle
plate shaft is 17:1.
2. There are 2 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. The in-series design has a separate motor housing.
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 when no
power is applied. This is for limp home reasons (the force of the plunger spring is 2 times stronger than the main spring). The default angle is
usually set to result in a top vehicle speed of 48 km/h (30 mph) Typically this throttle angle is 7 to 8 degrees from the hard-stop angle.
4. The closed throttle plate hard stop is used to prevent the throttle from binding in the bore (~0.75 degree). This hard stop setting is not adjustable
and is set to result in less airflow than the minimum engine airflow required at idle.
5. Unlike cable operated 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,
idle quality, and eliminates the need for an IAC valve.
6. The throttle position (TP) sensor has 2 signal circuits in the sensor for redundancy. The redundant throttle position signals are required for
increased monitoring reasons. The first TP signal (TP1) has a negative slope (increasing angle, decreasing voltage) and the second signal (TP2)
has a positive slope (increasing angle, increasing voltage). During normal operation the negative slope TP signal (TP1) is used by the control
strategy as the indication of throttle position. The TP sensor assembly requires 4 circuits.
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5-volt reference voltage
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Signal return (ground)
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TP1 voltage with negative voltage slope (5-0 volts)
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TP2 voltage with positive voltage slope (0-5 volts)
Accelerator Pedal Position (APP) Sensors