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  • Car Mechanics

    Diagnostics Doctor

    Jan 21, 2022 10 minutes

    BMW 3-SERIES

    Code 452A stored

    Q My wife’s car is a 2010 BMW 318d E91 with the engine code N47D20C and 135,000 miles. We have had the car since 2013, when it had 80,000 miles and a full BMW service history with 20,000-mile oil changes. Since then it has been serviced by me and the oil changed every 9000-10,000 miles using LL04 spec oil. The vehicle does a 30-mile commute to work three times per week on a mixture of roads and I assume it regenerates as required. Recently, on scanning the vehicle using my friend’s Snap-on Solus for a DSC fault (corrected by changing the ABS reluctor ring), I noticed the fault code ‘452A’ stored in the DME. Research shows this to be a time/age/mileage-based code as the DPF has reached a point where it should be considered for change. If ignored, other codes could be generated, necessitating DPF change. There are no other DPF codes present.

    Since then I have been trying to ascertain the actual level of DPF clogging to decide if repair/replacement is necessary, but the Snap-on live data doesn’t cover exhaust back pressure. According to a video on YouTube, voltage can be used but the test is demonstrated on an Audi, so the values may be different for BMW.

    Also, the BMW seems to have two exhaust pressure sensors, whereas the Audi only has one. Of the two pressure sensors, the front one connects close to the exhaust manifold via a two-part pipe that has a rigid and flexible section, while the rear sensor has a single flexible pipe and is more like the usual

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