Throttle Diagnostics

THROTTLE DIAGNOSTIC

The engine control module (ECM) checks its outputs to the throttle system for short circuits and open-circuits in the usual way.
The throttle unit and engine control module (ECM) mutually monitor each other and communicate via the CAN net. Monitoring takes place continuously and all DTCs are stored in the engine control module (ECM). The checks are based on plausibility tests, comparative tests and internal faults.
The accelerator pedal (AP) position sensor contains two sensors with two different types of signals; an analog signal and a pulse modulated signal. The accelerator pedal (AP) position sensor is checked by the throttle unit and the engine control module (ECM). The check is based on comparison and plausibility tests of the sensor signals. Normally the throttle unit is regulated by the analog signal. The role of the clutch and brake pedal sensors is to deactivate the cruise control when one of the pedals is depressed. This monitoring takes place in the engine control module (ECM). As well as the usual checks, the sensors are also checked for defects or faulty installation.
The role of the stop (brake) lamp switch is to provide the throttle unit and the engine control module (ECM) with the same signal so that a plausibility test can be performed.
When the diagnostic function detects a fault and the diagnostic trouble code (DTC) is stored, the system is reconfigured and substitute values are stored. Substitute values depend on fault type.

Substitute value:
- Fuel shut-off system which follows accelerator pedal (AP) position. Engine speed (RPM) is maximized by disabling the injectors, engine speed (RPM) is governed by the accelerator pedal (AP) position. Maximum engine speed (RPM) is approximately 5000 rpm
- Slower throttle opening than requested throttle opening. The throttle opens more slowly than normal requested opening because the system is only regulated by the pulse modulated signal from the accelerator pedal (AP) position sensor which is low-pass filtered.
- Throttle closure when braking. The accelerator pedal (AP) position is ignored when the brake pedal is depressed. The throttle unit maximizes permitted throttle opening.
- Throttle follows accelerator pedal (AP) position. The throttle and accelerator pedal (AP) are utilized as if they were mechanically connected to each other.
- Throttle disabled. Throttle is not affected and is in its mechanical stop position.
- Cruise control switched off.