A rattling noise from the exhaust tail pipe may be noted on 2012 BMW models equipped with the N54, N54T or N55 engine. The noise can last up to 60 seconds. The cause is insufficient vacuum to hold the exhaust flap shut. Note: There will be an audible one-time click from the exhaust flap when it opens or closes, which is a normal function.
Recommended parts for diagnosis include:
- 10cm of vacuum hose (P/N 11 72 7 545 323)
- One meter of vacuum hose (P/N 11 72 7 545 323)
- Vacuum line T-fitting (P/N 11 72 1 439 973)
- Vacuum line straight fitting (P/N 11 72 1 803 012)
If the engine is cold: The DME will actuate the exhaust flap for approximately 60 seconds once the engine is started. Measure the vacuum at the IMIB during this actuation phase. If there are no leaks in the system, the IMIB should read 0.3 to 0.0 bar while the exhaust flap is actuating (the flap is closed).
If the engine is at operating temperature: The exhaust flap can also be actuated manually through the ISID. Follow the necessary steps in the test plan “B1214_TVD_AGK – Exhaust flap.” The exhaust flap actuates for approximately 30 seconds during the test. The engine needs to be shut off and restarted during each test attempt. Measure the vacuum at the IMIB during this actuation phase. If there are no leaks in the system, the IMIB should read 0.3 to 0.0 bar while the exhaust flap is actuating (the exhaust flap is closed).
If the reading is higher than 0.3 bar:
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