I replaced the engine in my 06 with an 07 N52. It runs but with a bunch of error codes. Original engine ran without any codes. Replaced it due to scored cylinder wall, low compression. Takes about 3 to 5 seconds of cranking to start but runs smoothly. Many codes seem to point to a crank sensor. Also shows trans error so it only runs in 2nd gear. Replaced crank sensor with BMW official sensor. NO change. Loosened crank sensor to see if that would change anything. It ran pretty roughly with crank sensor loose so it apparently is getting a crank sensor signal. Tightened it up again, back to the same issue. Scan tool shows 2 rpm readings, both within 40 rpm of each other. Intermittently the dash tach will blip down 200 to 400 rpm at speed (2000 to 4000 rpm) I've been trying to find if there are any differences between the two model year engines but BMW dealer said all N52s are the same. Is it possible that the crank sensor gear is different between the two years so the DME and ECU are confused? 07 engine on an 06 DME / ECU?
did you recode the car for the new engine?
No. Didn't think it necessary or possible. According to BMW dealer all N52's are the same. But recoding seems to make sense after all we've checked. Exactly what would recoding do? especially if all N52's are the same. The only thing I can think of is that the crank sensor gear has a different pattern that may be "serialized" to the engine and that would be very crafty of BMW but possible.
I didn't see any video in BMW workshop that pertains to what I did. The videos show that the computers have to be recoded if you add something to the engine that wasn't there originally and that makes sense. Nothing functional or electrical was changed in my case. Just the mechanical complete rotating engine. In fact, the original crank sensor from the original engine was installed into the replacement engine. Not sure which video do you think pertains?
I finally found the problem. It seems that the mechanic who changed the engine broke the original crank sensor connector and replaced the pins. But he got them wrong!!!. This was discovered by viewing a number of You Tube videos and I happened to see the correct color code for a brief second on one of them.
I was able to get a new connector and contact pins from the dealer as separate parts. Total cost of about $30.
I had to crimp extension wires into the new contact pins myself. This can really only be done correctly with a special contouring wire crimper made for that type of connecting pin. I have that tool in my work tool kit because I do machine wiring. Then I connected the new wires to the old ones with a splicing connector because the originals were cut a bit short so they wouldn't reach the connector without a fight.
I checked the signal output of the crank sensor on the bench with an oscilloscope wired both ways. The wrong way didn't produce any signal while the correct wiring showed a clear signal. So why did the car run at all? I thought the engine wouldn't run without a crank sensor signal????
If it will run in limp mode without a crank sensor signal why doesn't the dealer know this???
FYI, I did ask the dealer about the correct color code way early in this process and they were not forthcoming with the info. I could have fixed this three weeks ago with that info!!
They suggested that we bring the car in for another analysis and diagnosis for an estimated $1000.!!!
Aren't BMW's Great!!