What it usually turns out to be
The code names cylinder 1, and the logic is the same whichever cylinder its siblings name. Ignition is the first branch: swap the coil with a neighboring cylinder and see whether the misfire follows it. A misfire that moves with the coil is solved; one that stays points at the plug, the injector or compression.
On the N54 there is a second branch BMW documents itself. Its high-pressure pump bulletin, SI B12 55 06, lists misfire codes on several cylinders — 29CC, 29CE, 29CF, 29D0 and 29D2 among them — stored beside 29DC, 29F2 or 2FBF when rail pressure is low. Misfires on several cylinders with a fuel-pressure code are a fuel problem, not six bad coils.
What gets replaced first, and why that is wrong
Full sets of plugs and coils get sold for a single-cylinder code, and on the N54 injectors get quoted before anyone has looked for a fuel-pressure code stored alongside. The coil swap and a read of the rest of the fault memory come first.
From a documented source: BMW SI B12 55 06 (N54 fuel pressure).
Seeing 29CD on your car?
I come to the car, read the modules and trace the fault to the actual wire, connector or module.
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