Leakage Diagnostic - Volvo B6324S Functional Description

Vapor that evaporates from the fuel in the fuel tank is
routed to and stored in the EVAP canister from where
it is introduced into the combustion process via the
Canister Purge (CP) valve.
A leak diagnostic has been introduced in certain mar-
kets to ensure that there are no leaks in the fuel tank
system. The diagnostic is designed to detect leakage
Reference
Orifice
Leakage diagnostic (LD) is performed in after run mode, when key off.
The diagnostic is divided into different phases as
follow:
Reference leak measurement, performed every LD
Rough leak test, performed every DCY
Small leak test performed every second DCY when
enabling conditions are met.
The diagnostic is performed by measuring the LD
Pump Module Motor current and then compares it to
a specified reference current. If a fault is detected in
any of the phases the diagnostic is interrupted and the
DTC for the component identified is stored. Diagno-
sis is carried out in the following stages: At the first
engine stop after refueling, the module
12

Leakage diagnostic

To canister
corresponding to a 0,20 inch or larger hole. The fuel
tank system consists of fuel tank, fuel filler pipe,
EVAP canister, CP valve and all pipes between these
components. To be able to diagnose the fuel tank
system, it is also equipped with a diagnostic module
(DMTL = Diagnostic Module Tank Leakage) inclu-
ding the electrical driven air pump.
Fresh air
DMTL will start if conditions are met (conditions for
soak time and fuel level are over ridden). When the
fuel level sensors are working correctly and the fuel
level is higher than 85 % or smaller than 15 % all lea-
kage tests are aborted. Also, the test is aborted if the
initial rate of change is higher than a calibrated level
due to a combination of high fuel level and high eva-
poration. In case of healing attempt the test is aborted
when the fuel level is too high, which is calibrated
lower than 85 %. While the fuel level sensors are not
working correctly the test only will be aborted if the
initial rate of change is higher than a calibrated level.