Leak Diagnostic Unit (Certain Markets Only)

Courtesy of VOLVO CARS CORPORATION

The leakage diagnostic unit's function is to pressurize the tank system for leakage diagnostics.

The leak diagnostic unit consists of a plastic housing with: 

1. electrical air pump
2. a valve / solenoid which governs the air flow in the unit
3. 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).

When leakage diagnostics is not active, the valve is kept open to ambient air so that EVAP-control can be performed.

At leakage diagnosis, the pump in the leakage diagnostic unit will start, and the valve in the leakage diagnostic unit will be controlled by Engine control module (ECM) by grounding the various circuits internally in Engine control module (ECM).

Engine control module (ECM) checks sealing in the fuel tank system by pressurizing the system and at the same time monitor a number of relevant parameters. Also refer to: LEAK DIAGNOSIS, IMPROVED VERSION (CERTAIN MARKETS ONLY)

The engine control module (ECM) can diagnose the leak diagnostic unit.

The valve in the leakage diagnostic unit can be activated.

The leak diagnostic unit is at the upper front edge of the fuel tank.