Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSBMW2013128I 2D CONVERTIBLE, ENG CD N52, STANDARD TRANSREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 73 (ENGINE CONTROLS - SYSTEM & COMPONENT TESTING)ENGINE SENSORS & SWITCHESFUEL TANK PRESSURE/LEAK DETECTION SENSOR7-SERIES
2013 BMW 128i 2D Convertible, Eng CD N52, Standard Trans
Fuel Tank Pressure/Leak Detection Sensor: 7-Series
2013 BMW 128i 2D Convertible, Eng CD N52, Standard TransSECTION 7-Series
WARNING: This page does not describe the selected car, but rather 37 other vehicles, including the 2005 BMW 760i, 2004 BMW 760Li, 2003 BMW Z8, 2003 BMW Z4, and 2003 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
- Evaporative leakage detection is performed on fuel storage system by Tank Leakage Diagnostic Module (DM-TL) pump which contains an integral DC motor that is activated by ECM. ECM monitors pump motor operating current as the measurement for detecting leaks. DM-TL generates a pressure of.29-.43 psi (20-30 mbar) in the fuel tank and evaporative system. Electrical current required for this is calculated by ECM and serves as the indirect value for the tank pressure. The DM-TL carries out a reference measurement before each measurement. This is performed by building up a pressure for 10-15 seconds using an internal orifice of.019" (.5 mm) as a reference and ECM monitors current (20-30 mA) required by pump motor.
- If a lower pressure is detected in pressure build-up (low current draw) as compared to reference measurement, this indicates a leak in fuel tank/evaporative system. If a higher pressure is detected (higher current draw), the system does not have a leak. The pump also contains an ECM controlled change over valve that is energized closed during a leak diagnosis test. The ECM only initiates a leak diagnosis test every second time the criteria is met. The criteria is as follows:
- Engine off with ignition off.
- ECM still in active state or what is known as "follow up mode". (ECM relay energized, ECM and components online for extended period after key off).
- Prior to engine/ignition switch off condition, vehicle must have been driven for a minimum of 20 minutes.
- Prior to minimum 20 minute drive, vehicle must have been off a minimum of 5 hours.
- No faults in ECM for DM-TL/tank venting system.
- Fuel tank capacity must be between 10-90 percent (safe approximation between 1/4-3/4 of a tank).
- Ambient air temperature between 19-95°F (-7-35°C).
- Altitude less than 8202 feet.
- Battery voltage between 11.5-14.5 volts.
- When these criteria are satisfied every second time, ECM will start FUEL SYSTEM LEAK DIAGNOSIS TEST. Test will typically be carried out once a day. The following morning, the test will run again.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.