XC90 AWD V8-4.4L VIN 85 B8444S (2005)
the different circuits internally in the engine control module (ECM).
The Engine control module (ECM) checks the fuel tanks system for leaks by pressurizing the system and at the same time monitoring a number of
relevant parameters. Also see: Leak diagnostics (certain markets only) See: Powertrain Management/Computers and Control Systems/Description and
Operation/Leak Diagnostics (Certain Markets Only)
The engine control module (ECM) can diagnose the leak diagnostic unit.
The valve in the leak diagnostic unit can be activated.
The leak diagnostic unit is at the upper front edge of the fuel tank.
Air conditioning (A/C) compressor (check valve Air conditioning (A/C) compressor)
The air conditioning (A/C) compressor transports refrigerant, which is necessary for air conditioning (A/C) operation. It is an axial piston compressor
with variable displacement. I.E. The compressor has adjustable cylinder displacement which is controlled by a check valve (solenoid). The valve, which
is underneath the compressor, can be replaced.
The air conditioning (A/C) compressor is directly mounted on the engine block and is powered by the engine crankshaft via the auxiliaries belt. For
further information, see Climate control and Design and Function, Climate control module (CCM).
Air conditioning (A/C) relay
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 / opening 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.
Starter motor relay