THROTTLE POSITION (TP) SENSOR
See: ELECTRONIC THROTTLE UNIT
Scheme 578
The function of the accelerator pedal (AP) position sensor is to provide the engine control module (ECM) and central electronic module (CEM) with information about the position of the accelerator pedal. This data is used by the engine control module (ECM) to deploy the shutter in the throttle unit to the correct angle.
The sensor consists of a plastic housing with circuits. The output signals are a pulse width modulated (PWM) signal and an analog signal related to the accelerator pedal (AP) position.
These signals indicate the position of the accelerator pedal (AP). The pulse width modulation (PWM) signal is transmitted to the engine control module (ECM). The analog signal is transmitted to the central electronic module (CEM) and on to the engine control module (ECM) via the controller area network (CAN).
Normally the pulse width modulation (PWM) signal is used to regulate the throttle angle. In the event of a fault in the pulse width modulation (PWM) signal the analog signal is used as a replacement, unless this is also diagnosed as faulty.
The sensor is supplied with 12 V by the system relay via a fuse and is grounded in the car body.
The pulse width modulation (PWM) signal is also used in conjunction with the analog signal for accelerator pedal (AP) position sensor diagnostics. The accelerator pedal (AP) position sensor signals can be read using VIDA (Volvo scan tool). A diagnostic trouble code (DTC) is stored if the engine control module (ECM) detects a difference between the analog and pulse width modulation (PWM) signals. The engine control module (ECM) then uses the signal with the lowest value for regulation.
The accelerator pedal (AP) position sensor is located on the accelerator pedal bracket.
Scheme 579
Engine control module (ECM) receives information about the clutch pedal's position in two ways.
Partly from a clutch pedal position sensor which is directly connected to Central electronic module (CEM), and partly from a clutch pedal switch directly connected to the Engine control module (ECM).
The function of the clutch pedal switch is to provide extra safety for the function autostart. In order for the function to be activated, the Engine control module (ECM) must receive signal that indicates pressed down pedal from the clutch pedal switch.
To start without the function autostart it is enough that any of the signals (from clutch pedal position sensor or clutch pedal switch) indicates pressed down pedal.
In its starting position, the clutch pedal switch is open (clutch pedal released). The switch's installation shall be adjusted so that it is closed when the clutch pedal passes 75% of full pedal movement.
The clutch pedal switch is on the pedal box by the clutch pedal.
The engine control module (ECM) can diagnose the clutch pedal switch. The status (position) of the switch can be read using the diagnostic tool.
Note. Read-out only works on vehicles built after week 46 2007.
Scheme 580
The function of the main relay (system relay) is to supply certain components with voltage.
The relay is mechanical and has a closing and opening function. In the rest position the circuit in the relay is open.
The main relay terminals (#30 and #86) are supplied with voltage by the battery. When the ignition key has been turned and the engine control module (ECM) is powered, the terminal (#85) on the main relay is grounded by the engine control module (ECM).
When the terminal (#85) is grounded, the relay is activated and a number of components are powered via the relay terminal (#87).
The main relay is in the integrated relay/fuse box in the engine compartment and is diagnosed by the engine control module (ECM).
Scheme 581
The air conditioning (A/C) relay supplies the A/C compressor with voltage. The relay is controlled by the engine control module (ECM) based on information from different signals
- the climate control module (CCM) (via the control area network (CAN))
- the engine coolant temperature
- the position of the accelerator pedal (AP)
- the pressure in the system.
The engine control module (ECM) can temporarily disengage the A/C compressor during wide open throttle (WOT) acceleration.
The relay is mechanical. It has a closing / breaking function and is supplied with power from the system relay.
In the rest position the circuit in the relay is open.
The system relay supplies the coil and the relay with power. The relay activates when the coil is grounded in the engine control module (ECM), the circuit closes and the A/C compressor is supplied with power via the relay voltage output.
The relay coil is grounded (signal) when the engine control module (ECM) receives a signal via the Controller area network (CAN) from the climate control module (CCM) to activate the relay and start the compressor.