EMS Sensors (page 4 of 13)

ENGINE MANAGEMENT SYSTEM - SIEMENS

DESCRIPTION AND OPERATION 18-4-17

The ECM monitors the output signals from the APP sensor and determines the position, rate of change and direction 
of the throttle pedal movement. The ECM stores values which relate to closed throttle and wide open throttle and can 
adapt new values to compensate for component wear or replacement.

The ECM uses the closed throttle APP sensor signal to initiate idle speed control and enable an overrun fuel reduction 
strategy.

The APP sensor signals are also broadcast on the CAN bus and are used by the EAT ECU to determine the correct 
points for gearshifts and kickdown.

The ECM supplies a regulated 5V output to the APP sensor and an earth path for the potentiometer tracks. The earth 
path is also used as a screen to protect the integrity of the signals.

If the APP sensor fails to output a signal, the ECM uses a fail-safe mode which increases the idle speed to 1250 rev/
min. The ECM will not respond to movement of the throttle pedal. In the event of a total failure to output a position 
signal, the following symptoms will be observed:

l

No throttle pedal response

l

Failure of emission control

l

Automatic transmission kickdown inoperative.

The APP sensor can be tested using the following procedure:

1 Apply a 5V supply to pins 1and 2. Connect pins 4 and 5 to earth.
2 With the sensor in the idle position, check the output voltage at pin 3 – the reading should be approximately 

0.73V.

3 With the sensor in the idle position, check the output voltage at pin 6 – the reading should be approximately 

0.36V.