General Information

Air Management




Throttle Valves




The mechanical throttle valves regulate the intake air flow and are operated by an Electronic Throttle Actuator (1 EDR).

The throttle valves are an assembly of six individual throttle housings linked by a common shaft. The throttle opening depends on engine rpm and load (1000 kg/h maximum air flow).

Refer to the Repair Instructions for throttle adjustments.

Accelerator Pedal Position (PWG)







The accelerator pedal module (E46 M3) provides two variable voltage signals to the ECM that represents accelerator pedal position and rate of movement. The ECM will activate the EDR and Idle Air actuator based on the request.







Dual Hall sensors are integral in the accelerator pedal module. The ECM compares the two values for plausibility.

The M roadster and M coupe use a remote mounted PWG. This type uses twin potentiometers to produce the same input signals (voltage) as the Hall sensors.

The ECM provides voltage (5v) and ground for the Hall sensors. As the accelerator pedal is moved from rest to full throttle, the sensors produce a variable voltage signal.







Hall sensor 1 (request) = 0.5 to 4.5 volts
Hall sensor 2 (plausibility) = 0.5 to 2.0 volts

If the signals are not plausible, the ECM will use the lower of the two signals as the request input. The throttle response will be slower and the maximum throttle response will be reduced.

The potentiometer PWG produces the same voltage signals to the ECM.

Electronic Throttle Actuator (EDR)







The EDR is specifically designed for the S54 engine. This allows one actuator to operate all six throttles via a common linkage.

The ECM provides the operating voltage and ground to the EDR for opening and closing the throttles. The ECM monitors a feedback potentiometer located on the actuator shaft (arrow) for actuator position/plausibility (closed 4.5v - full open 0.5v).

There is a return spring fitted to the actuator lever end that assists in closing the throttles.

Throttle Valve Position




A potentiometer is fitted to the end of the throttle shaft (arrow) that allows the ECM to monitor throttle position.

This signal is used by the ECM for a position/plausibility check (closed 0.5v - full open 4.5v).

Idle Air Actuator







The Idle Air Actuator is a two-coil rotary actuator (ZWDS). The S54 features a second air supply system that functions independent of the throttle valve control system (EDR). This actuator regulates air by-passing the throttle valves to control low engine speed.

The valve is supplied with operating voltage from the ECM Relay. The ECM is equipped with two final stage transistors which will alternate positioning of the actuator. The final stages are "pulsed" simultaneously by the ECM which provides ground paths for the actuator. The duty cycle of each circuit is varied to achieve the required idle RPM.




The valve (2) regulates air flow through an external air distribution pipe to the individual throttle housings. The inducted air is shared between the idle actuator and throttle valves depending on the engine load. The maximum air flow of the idle air actuator (80 kg/h) permits emergency operation of the vehicle (limp-home mode).

Hot-Film Air Mass Meter (HFM)




The air volume input signal is produced electronically by the HFM which uses a heated metal film in the air flow stream. The HFM housing is integral with the air filter upper housing (one-piece).

The ECM Relay provides the operating voltage. As air flows through the HFM, the film is cooled changing the resistance which affects current flow (voltage drop) through the circuit as the resistance changes. The ECM monitors this change regulating the amount of fuel injected.

If these components/circuits are defective, a fault code will be set and the "Malfunction Indicator Light" will be illuminated when the OBD II criteria is achieved.

Air Temperature Signal







The HFM contains an integral air temperature sensor. This is a Negative Temperature Coefficient (NTC) type sensor. This signal is needed by the ECM to correct the air volume input for changes in the intake air temperature (air density) affecting the amount of fuel injected, ignition timing and Secondary Air Injection activation.

The ECM provides the power supply to this component. The sensor decreases in resistance as the temperature rises and vice versa. The ECM monitors an applied voltage to the sensor that will vary as air temperature changes the resistance value.

If this input is defective, a fault code will be set and the "Malfunction Indicator Light" will be illuminated when the OBD II criteria is achieved. The ECM will operate the engine using the Engine Coolant Sensor input as a back up.

Suction Jet Pump




The ECM regulates the Suction Jet Pump (1) to provide sufficient vacuum for the brake booster under all operating conditions. The ECM controls the Suction Jet Pump Solenoid (2) to allow vacuum flow through.

Additional vacuum compensation is applied to the brake booster when the circuit is "deactivated" (solenoid sprung open).

Vacuum enhancement is limited to the brake booster when the control circuit is "activated" (solenoid powered closed).