Checking Fuel Tank & Tank Venting System For Leaks With Tank Leakage Diagnosis Module (DM-TL) - 7-Series (E65/66)

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An OBD fault is indicated by CHECK ENGINE light in instrument cluster. This may indicate a leak in the tank venting system. Information on this is provided by the fault memory of the DME control unit. Read out fault memory of DME control unit and carry out diagnosis in accordance with faults stored. See Fig 1 and Fig 2 . A leak test with the DM-TL module is then carried out if:
- The components of the DM-TL module are okay.
- A error is stored in the DME fault memory (tank leak detected).
Fig 1: Identifying Fuel System Components (7-Series V8)
Courtesy of BMW OF NORTH AMERICA, INC.

Fig 2: Identifying Fuel System Components (7-Series V12)
Courtesy of BMW OF NORTH AMERICA, INC.
To carry out a correct leak test, ensure content of fuel tank is less than 90 percent and reserve indicator lamp is off. Leave car in workshop for at least 2 hours so that fuel temperature comes into line with workshop temperature. Ideal fuel temperature is approximately 50-68°F (10-20°C). Do not under any circumstances fill up car with fresh fuel as there is a strong exhalation of fresh fuel. Check that tank cap is correctly seated.
WARNING: During leak test, under no circumstance apply external pressurization through the tank filler neck as this may cause an incorrect reading.
Clear DME fault memory. In Diagnosis and Information System (DIS), go to FUNCTION AND COMPONENT SELECTION page. Carry out tank leakage diagnostic module. If a fault is stored again in DME fault memory (tank leak detected), carry out leak testing. Go to CONDUCTING LEAK TEST ON FUEL TANK & TANK VENTILATION SYSTEM .