2006 BMW 525xi with the N52, an oldie.

This one was a fairly simple one, but oddly satisfying to fix. The complaint was a check engine light on, and the engine was running rough.

2E31 fuel injector, cylinder 2, activation trouble code was set in the engine module. This code means the engine module is not seeing cylinder 2 fuel injector firing. With the vehicle idling in my bay. With the scan tool, I go into the engine module, then into the engine data menu. There is a set of data called "smooth running values", other manufacturers call it cylinder contribution. Each time a cylinder fires, it accelerates the crankshaft. The engine module knows what cylinder is firing and how much it should speed up the crank. The engine module calculates how much each cylinder is contributing and displays a number for each cylinder. All cylinders are + or - 100, except cylinder 2. It stuck at -400, so not firing at all.

I removed cylinder 2 spark plug. The plug is a bit carbon fouled but not too bad. I look through the spark plug hole and inspect the top of the piston, there is slightly more than normal carbon build up but is dry and not fuel soaked, so that's good. I put the plug and coil back in and unclip the fuel injector connector cover. Start the engine and back probe injector 2 power supply at the connector with my oscilloscope. I have a solid 14v and no injection event. I back probe cylinder 1 and have a normal injection waveform. These injectors are supplied key on power, the engine module grounds the circuit to fire the injector. Most automotive circuits are ground controlled. We have a few options at this point. It could be a circuit integrity problem, an engine module driver problem, or a bad injector. Seeing I'm already right at the injector connector, and a bad injector is the most likely cause. I measure the resistance of the injector. Resistance testing has a narrow scope of were it is an effective test, especially on induction devices. But, I'm looking to see if the solenoid windings are open. Cylinder 2 injector has a resistance of 20 000 ohm's basically open. Cylinder 1 has 12 ohm's.

I install a new injector in cylinder 2. The engine now runs smooth. Cylinder contribution is equal for all cylinders and no trouble codes have set.

I hope this helps or inspires.