Hey guys - Need a little help. Bessie wouldn't start a couple of days ago and I thought it was the battery. I left my lights on for just under an hour before I figured it out. She started right up and I took a couple short trips before parking for the night. Next day, no crank, no start. Battery was at least 4 years old with at least two previous episodes of leaving the lights on before, so figured it was now toast. Tried to jump it, charged it for a couple of days and finally replaced it with an Autozone Duralast H8-AGM battery. Still no crank, no start.

Bessie has about 159k on her so I figured her Denso starter was on its last legs too. Got a reman Bosch starter and new bolts and proceeded to replace the Denso. What a PITA. Finally got it in but only after snapping the CCV hose connected to the valve cover and intake manifold... Replaced the CCV vent hose and I believe I got everything reconnected correctly and tried to start her. She started up with a slow crank (about 4 seconds) which felt like an eternity but she got started. Had a bunch of errors on display (4x4, start up assistance inactive and DSC and transfail mode) All cleared by themselves except trans fail. Drove her to our garage around back to read the codes. (Starter died in front of the house and I had to replace it outside in 80 degree weather. FML)

No luck doing adaptation reset or turn power off/on, fail safe/limp mode remains lit. Engine sounds great, no smoke, clicking or sputtering. Just slow crank and fail safe mode are constant.

Registered the battery using INPA and then read the codes as follows:
MSV70 Error memory

2E98 (P3225) Generator Communication Error

2A94 (P0335) Crankshaft Sensor 'A' Circuit

2C9D (P0050) HO2S Heater Control Circuit (Bank 2 Sensor 1)

Transmission Error Memory
51A7 (P1727) Signal (engine speed) from the ECU is wrong/CAN Engine Speed


I've got Bessie on a trickle charger tonight to beef up the charge even though it is a 3 day old battery. Hoping that low charge might clear the fail safe/limp mode. It's a BMW after all, so not the first time its been in limp mode, but usually it has taken care of itself in the past. I've changed the fluid, pan and filter a little over a year ago, so no issues there. Still need to replace the solenoids to stop the 1/2 jerk etc, but more so annoying rather than limp mode triggering.


If you guys have any ideas, I'm all ears. I'm stumped at this point... Thanks in advance.

(Cross posted on Bimmerfest for more eyes/input)

 

I think Crankshaft Position sensor is the cause for trans error [and possibly slow start].

Crankshaft Position sensor is just below the starter. Unfortunately, you'll have to undo the intake manifold again and replace CPS.