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      01-09-2021, 03:00 AM   #1
Thomachaan
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Drives: BMW 328xi
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Duplicate - Please Delete

Hello, I'm going to diagnose my BSD line and need help to rule out my DME, would appreciate any help and advice, specifically on whether a signal should be present if all BSD users are disconnected (IBS, alternator, waterpump, and oil condition sensor). I'll have an oscilloscope, amp clamp, and new Bosch starter in the next few days, and while replacing starter will check everything I can with the manifold out (like the crank sensor). Car has not been driven since this occurred.

I caused the issue. Finished the valve cover job but left one of the overhead ground straps undone. Engine started fine but while running I tried placing the strap back on and caused a HUGE spark that shut the engine down. In the past two weeks I've only gotten it to start once briefly. Based on what I read in searches, issues resulting from those ground straps can possibly take out everything on the BSD line including DME. There's not a lot of info out there on how to test individual modules and parts unplugged.

My car is a 2009 BMW 328i xDrive, N51 engine. The only code which reappears from DME after clearing is 2E7C. Other issues that show up on iDrive and dash are Passenger Restraint Malfunction, transmission malfunction (I don't think the gear shifter is actually shifting gears now) and "P" not engaged, and DSC/AWD malfunctions (sometimes turning the steering wheel all the way left and right clears, sometimes it doesn't). INPA only shows DME 2E7C when checking Functional Jobs. When key is switched to ignition on, the water pump runs (maybe full speed). That makes sense, it's running on emergency mode since there's a BSD error. Sometimes there's no crank (just hear clicks in engine bay), lately it cranks no start. Sometimes the key won't eject, I'm able to wiggle it out without breaking anything.

Car had no codes prior, just a bunch of oil leaks I wanted to take care of. This car came to me from a family member, I'm told it's on its original water pump. I personally drove the car from NJ to CA and back in the last 6 months, no problems along the way. It would start really slow nearly every time but always managed to start, summer and winter.

At the very least I need to get the engine running again to keep the internals clean, and diagnose each remaining electrical issue from there.

What I've checked:

-I opened the DME, pins and board look clean, no evidence of a burn.
-Checked the CAS3, key reader, and ignition button, no visual evidence of burns or damage.
-Pulled out every related fuse from the fuse box (and one 40A in ECU box), cleaned, and tested with a multimeter.
-Pulled out and tested 3 relays with a 9v battery (1 in glove box 'CAS relay' and two in ECU box). I also opened them up and cleaned out contacts. Turns out you can unclip the moving contact for easy cleaning access.
-Unplugged IBS, alternator, and oil level sensor in different combinations, no change in codes and no start.
-Pulled out positive battery cable, checked BST under plastic cover. Doesn't look like it blew. Tested the BST ignitor pins resistance, got ~0.2ohms. I thought it'd be closer to 1 or 2 based on online hacks connecting a 1-2ohm resister to fool the plug.
-Pulled out negative battery cable, no signs of corrosion at contact points and no visible issue inside plastic casing. The IBS itself is too integrated with the terminal to open up further to check out.

What I'm going to check:

-Back probe BSD line with nothing connected, and PT-CAN line (possibly what's causing all the other issues).
-Fuel pressure, then the regulator and pump if there's an issue.
-Battery check at an auto parts store.
-Throttle body function (need to find out how to electronically move the throttle plate to see if it works).
-Trace wires connected to that ground strap, and trace grounds and BSD pins in DME to transistors/IC's. I have a soldering rework station for anything that needs replacing. Otherwise I'll need a new DME/CAS/key set and coding, and I'd be down 1 key after recently getting a spare from dealer =(

I'll post as I move along. I'm taking pics and videos when I remember, but it feels useless till I reach some level of success with this. Been greatly appreciating all the info I've found on this forum. I couldn't have gotten this far without this place.

Last edited by Thomachaan; 01-10-2021 at 01:58 AM.. Reason: Duplicate - Please Delete
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arc, back probe, bsd, crank, diagnose, dme, electrical, no start, oscilloscope, spark

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