First post, first mistake, not the first time my 128i is stuck in the garage

[bourski]

New to this site, found it while cruising the internet for answers to my own crank-no start problem. First lesson, find the right forum to put my question in. Sorry, 1Mers.

I have a 2011 128i N51 SULEV with 115k miles. It cranks, but there’s no spark on any of the cylinders. I recently replaced the starter and the crankshaft position sensor. I think the constant voltage at the coils is good and I have good ground indications. I get zero voltage on the third coil wires when cranking, hence no sparks. I think I’ve pulled and tested every fuse behind the glove box; any other places BMW would have hidden ignition fuses I should check? The battery is sound, another relatively new purchase. I think unrelated, but I’ll mention anyway, Fuel pressure at the rail is 70 psi when cranking, and I hear the hpfp kick on when it’s supposed to, so I’ve ruled out fuel as the problem.

I’m looking for any additional things I should check before go down a bad computer or CAS rabbit hole.

[jdt10768]

can you hook up an OBD scanner and see fault codes?

[bourski]

I have a Bavarian Technic cable and software. The codes I have are:

A6CF - Sensor AUC. Short circuit or signal interruption
A0B4 - Fault engine start starter
A10A - EWS4 timing challenge/response error. Timeout
578E - Gearbox control unit. Short circuit or signal interruption
2A9A - Camshaft sensor inlet, signal. Short circuit or signal interruption

[cerealwars]

Sounds like you may want to try a new camshaft position sensor, or at least start by putting eyes on yours. Maybe it is unplugged or the wiring got bumped/frayed somehow? Good news is they're not too expensive.

[tracer bullet]

Originally Posted by bourski

A6CF - Sensor AUC. Short circuit or signal interruption
A0B4 - Fault engine start starter
A10A - EWS4 timing challenge/response error. Timeout
578E - Gearbox control unit. Short circuit or signal interruption
2A9A - Camshaft sensor inlet, signal. Short circuit or signal interruption

Google / forums here say A6CF AUC sensor is related to the A/C, so it shouldn't matter for this.

A0B4 seems really generic, hard to find info, it's almost like the car is telling you the obvious - it doesn't seem to be starting, as opposed to a specific issue.

A10A looks to be worth exploring more. Indicates a timing issue?

578E looks to be an indicator for transmission fluid life, can probably ignore for this.

2A9A - Cam Position Sensor. Another one I would suggest to focus on.

I think cerealwars is right for where to start. Unplugged, broken wire, seated correctly, maybe replace it.

Also suggest being sure your battery is charged - keep it on a trickle charger so you don't drain it trying to start the car.

[bourski]

Thanks. I’ll check those recommendations next

[bourski]

So both camshaft sensors checked out - good voltage and functional. Still scratching my head on this one. If I had any hair, it wouldn’t hurt so much.

[bourski]

So, the car is still in the garage, still no spark at the coils. I think it’s time for some wire tracing and voltage checks, but I’m not sure where to start. I have colored wiring diagrams and a few tools that I suspect might help. As I mentioned earlier, I have BT software and a cable. I recently downloaded Service & Repair Manual software, a huge OVA file, from eManualOnline. It appears to include scanning functions. If either of these programs can be used to read voltages without poking holes in wire bundles, I think that’s preferable to compromising a lot of wire insulation. I could use some guidance on how to do that from someone who’s been down this path.

[cerealwars]

Maybe check the grounds per this thread?

https://www.e90post.com/forums/showthread.php?t=1420619

I know you mentioned you already checked them, but maybe spend some more time lurking around under the hood. Retrace your steps, there must be something we're missing.

Also, though it might seem unrelated, the AUC sensor is easy to get to. Maybe give that area a look. Has anyone been under the hood for anything else recently before this issue cropped up?

[bourski]

A couple things puzzling me as I dig through the wiring diagrams and look at YouTube videos. In this video

he shows a fuse block under the hood. In the attached wiring diagram, I think that block is in the red box. In the picture, the green box shows a bundle of capped off wires and is the only spot where I think this block could have been. Where did it go? FYI, I checked the relay in the red box, it’s good.

I’ve checked the grounds and retraced everything else I can think of, including taking out the intake manifold to check the connection box next to it, and recheck the new starter connections. No recent work had been done to the car prior to its current issue.

I’ve done a bit of reading about the CAS-ECU-fob relationship, wondering if the car developed a sync issue. The car recognizes both fobs as they open the doors, power up the dash, and allow the starter to crank. I also think the ECU is working properly, as I’m able to read real data from the sensors on my BT software. I wonder if something in the anti-theft system would allow cranking but no spark?? Would that be CAS or ECU characteristic?

One unrelated question also, if I may. Is there a trustworthy ISTA download out there, short of going to BMW with bags of cash? I paid eManual online for one that requires downloading an ancient Windows 7 virtual machine to run it. Touted by them as fully capable ISTA. A $500 notebook computer and numerous customer service emails later, they finally admit the software they sell won’t connect to the car, because their VM does not have port drivers installed (or available) to support connecting an ODB2 cable. Lesson learned.