EMS Sensors (page 2 of 13)

ENGINE MANAGEMENT SYSTEM - SIEMENS

DESCRIPTION AND OPERATION 18-4-15

The ECM stores the signal values that correspond with closed and wide open throttle, and adapts to new values to 
accommodate component wear or replacement.

The signals from the APP sensor are monitored by the ECM for short and open circuits and plausibility. If a fault is 
detected, the ECM:

l

Stores a related fault code in memory.

l

Illuminates the SERVICE ENGINE warning lamp in the instrument pack.

l

Inhibits the driver demand message on the CAN bus, which disables the Hill Descent Control (HDC) function of 
the ABS modulator and reduces the performance of the automatic gearbox (harsh gear changes and loss of 
kickdown).

l

Adopts a throttle limp home mode.

The throttle limp home mode adopted depends on the nature of the fault:

l

If a fault is detected with one potentiometer track, the ECM limits vehicle acceleration by limiting throttle plate 
opening.

l

If a fault is detected with both potentiometer tracks, the ECM uses the throttle plate to run the engine at a fixed 
speed of 1472 rev/min while the brake pedal is released, and idle speed (750 rev/min) while the brake pedal is 
pressed or if there is a brake pedal sensor fault.

l

If there is a process fault in the ECM, the ECM either uses fuel injection cut-off to limit engine speed to 1300 rev/
min or disables fuel injection to stop the engine.