Leak Diagnostic Unit (Certain Markets Only)

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2006 Volvo S80, 2005 Volvo S80, 2004 Volvo S80, 2003 Volvo S80, and 2002 Volvo S80. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying Leak Diagnostic Unit

Courtesy of VOLVO CARS OF NORTH AMERICA.

The function of the leak diagnostic unit is to pressurize the fuel tank system during leak diagnostics.

The leak diagnostic unit consists of a plastic housing with:

electrical air pump
a valve / solenoid which governs the air flow in the unit
a heater element (PTC resistor) which warms up the pump.

The electrical pump, valve and heater element in the unit are supplied with voltage by the system relay. The pump, valve and heater element are grounded (control) in the engine control module (ECM).

NOTE:

On model years, 2002-2004 the heating element was controlled by the Central electronic module (CEM), but on request from the Engine control module (ECM).

During leak diagnostics the pump in the leak diagnostic unit starts. The valve in the unit is operated by the engine control module (ECM) by grounding 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)

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.