29F2

BMW wrote SI B12 55 06 around two complaints. A long crank of five to six seconds on a cold start or after a hot soak usually stores 2FBF alone. A car that loses power or runs poorly stores 29DC and/or 2FBF, and in some cases 29F1 and 29F2 as well, sometimes with misfire codes on several cylinders. 29F2 belongs to the second complaint.

For that complaint BMW's procedure is the ISTA test module for fuel pressure control, with one warning that matters: let the pressure settle for about 60 seconds at idle before taking the reading, or an implausible value near 150 bar goes into the test and it wrongly condemns the high-pressure pump. Because the fault may only show under load, BMW suggests a road test with a gauge on the low-pressure line — a low-pressure reading swinging between 5.0 and 7.0 bar points at the fuel delivery system.

The cause list is longer than the pump: the high-pressure pump and its diagnostic software, the electric in-tank pump or a clogged filter, the low- or high-pressure sensors, the pressure regulator, the volume control valve, an injector, and an intermittent wire or connector in the fuel delivery system.

The high-pressure pump gets quoted on sight, and injectors alongside it. In the US, BMW extended the N54 pump warranty to 10 years/120,000 miles on model year 2007–2010 E60, E61, E90, E92 and E93, 2008–2010 E82 and E88, and 2009–2010 E89 and E71 — a window that has now closed for every one of them — so the test module and the low-pressure reading have to come before the most expensive part.