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Posts: 215
Join Date: Sep 2017
Car: 2013 335i xDrive Coupe
Default 09-15-2021, 02:28 PM

Update if someone has similar issues: It may have been a bad ground wire connection between stranded wire and fork terminal.

It would go months between malfunctions, then have the warning+limp, and/or sputtering, and/or random gauge sweeps, sometimes three times in two days then nothing for more months. The last thing I had to try was rewiring the grounds, which I put off because I knew they were tight on bare body metal, and there was electrical continuity between strut tower, negative battery terminal, and engine block.

It got bad today with gauge sweeps and sputtering, so I parked and adjusted the grounds to "make sure". Even after disconnecting the battery the sputtering wouldn't stop, and no JB4 wheel controls, so I strongly suspected a ground wire issue. Without bothering to disconnect the battery, I noticed one (JB4 or PIC) would "pop" on metal and one wouldn't, so I pulled that fork off and tightened the nut on the bare wire. Started up fine and no car or JB4 errors yet, but since the problem is so intermittent I'm not sure it's gone. If you have an engine malfunction I recommend soldering the terminals to rule them out.
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