P1484

P1484

DMTL-Tank Leakage Diagnostics Module

Diagnostic conditions
- Vehicle speed = 0 km/h
- Engine speed = 0 rpm
- Correction factor, height > 0.73
- Coolant temperature upon starting the engine may be no more than 6.8 K above ambient temperature
- Coolant temperature when engine starts > 3.8 degrees C
- Period for which the engine needs to have been running before ignition is switched off > 20 minutes
- Ignition has been switched off for at least 10 seconds.
- Ambient temperature 4...35.3 degrees C
- Active charcoal filter load < 3 for minor leak
- Fuel tank fuel level 10 ...54 litres
- Battery positive voltage 11.02 ... 14.5 V
- No fuel tank filling
- No faults detected for ambient pressure sensor, coolant temperature sensor, vehicle speed sensor
- No output stage faults detected for DMTL pump motor, DMTL switchover valves and tank vent
- No fault detected for tank vent (flow)
- The diagnostic conditions can also be established using the PIWIS Tester via the short test "tank leakage test". After the test has begun, the ignition must be switched off.

NOTE: In this context, please also observe the function description.

Possible fault causes
- DMTL-Tank Leakage Diagnostics Module faulty

Function description

Tank leakage test/DMTL-Tank Leakage Diagnostics Module

NOTE: The tank leakage test is performed only on USA vehicles.

Construction of the tank leakage diagnostics module:
The diagnostics module consists of an electric motor with a small air pump, switch-over valves and a reference nozzle.
In addition, the module is heated so as to prevent the forming of condensation and ice.

Procedure of the function:
- The pump is operated via an electric motor and conveys air through the reference leak. The power consumed during this process is determined.
- The switch-over valve switches and the air current is now directed into the fuel tank. The power consumed during this process is also determined. After a waiting period dependent on the fuel tank fuel level, it must be at least as high as the power consumption was during the reference leak test if the tank system is leak-free.
- The system is identified to by leaking if the power consumption is lower during the actual leakage test as it was during the reference leak test.
- An evaluation of the power consumption levels when the pump is started and after the switch-over valve has switched serves to identify faults within the tank leakage diagnostic module (e.g. pump blocked, motor spins at idle speed, valve does not switch etc.).
- The diagnosis of heating, motor and switch-over valve is performed via the output stage of the DME control module.