Accelerator Pedal Module (APM)
The accelerator pedal module has, for safety reasons, 2 output signals which provide information about requested throttle opening simultaneously:
- One analog "Master signal" which is sent to the engine control module (ECM) which in turn requests throttle opening.
- One digital back up signal (Pulse width modulated) which is sent via the engine control module (ECM) to the electronic throttle module and is used when a fault occurs in the analog signal.
The accelerator pedal (AP) position sensor contains 2 potentiometers whose resistance varies with the accelerator pedal (AP) position.
Both are supplied with 5 V using a common cable but are grounded separately.
One signal is analog and goes straight to the engine control module (ECM). The output signal varies between 0.5 V - 4.8 V depending on the accelerator pedal (AP) position.
The other signal (Pulse width modulated) goes first to an analog digital converter where it is digitized and is sent via the engine control module (ECM) to the electronic throttle module.
On cars with automatic transmission the sensor contains a mechanical kick down marker which gives the driver kick down feeling when the pedal is depressed 80% of full depression.
The signal is sent on to the transmission control module (TCM) which then permits the kick down function. There is no longer a separate kick down switch in the sensor, as was the case in earlier versions.
There are several signals which pass through the engine control module (ECM) to continue directly to the electronic throttle module. These are the following signals:
- Brake Light Switch is used as a safety switch by the electronic throttle module when a signal is faulty or outside permitted range. If the cruise control is active when the brake light switch is activated, the electronic throttle module will only accept the pulse width modulated signal to control the throttle and disconnect the cruise control.
- Pulse width modulated signal (= duty cycle) is one of the two signals sent from the Accelerator pedal module to the electronic throttle module to control the throttle. The signal is digital and is a back up the ordinary analog signal sent from the Accelerator position module to the engine control module (ECM).