2016 F-350 6.7L Battery Light On

mchan68 · April 28, 2018

Just thought I would share one I had in this week. A 2016 F-350 6.7L in for a Check Engine and Battery lights on. DTCs retrieved were P0563 and P0625 in the PCM, along with DTCs for "system voltage too high" in every other module on the network. Long story short, circuit SDC14 (RD) was open with green death between C1104A and S137, closer to S137. The alternative to repairing this circuit would have been to replace the main battery, generator and starter cable assembly. Already done that one before for a different concern, NO THANK YOU.

Keith Browning · April 29, 2018

Mike I have run into that fault before - the system overcharges because that circuit loses it's integrity and of course you know why as you mentioned. I have attempted repairs to that circuit several times but it's usually difficult due to the lack of working room. My fix is to cut that circuit 2" from the connector on the alternator, splice in 6" of 20 gauge fusible link and an eyelet. I neatly retape the harness to look normal and then connect the eyelet to the alternator b+ post.

I really hate that lower harness that wraps around the engine. All they needed to do was wrap the wiring in tape properly (and completely) and we would not see these problems. Funny how more often than not it's the battery sense circuit that chafes.

mchan68 · April 29, 2018

1 hour ago, Keith Browning said:

I really hate that lower harness that wraps around the engine. All they needed to do was wrap the wiring in tape properly (and completely) and we would not see these problems. Funny how more often than not it's the battery sense circuit that chafes.

EXACTLY why I declined to provide a quote to replace that harness. Well that, and the fact that this vehicle was out of warranty. I had replaced that same harness before on another truck awhile back for the main starter cable completely rotted out, but that truck still had warranty and there wasn't any repair kit I was able to source for that heavy of a gauge of wire. The price of the harness wasn't all that unreasonable. It was remembering how horrible that job was, that made me decide to repair that circuit. I tried uploading photos of where I finally found the open, but apparently my files are too large to upload. And of course, as my luck would have it, the open was in a very tight area to access. It was by the plastic wire loom holder, where a 10mm nut secures the transmission fluid cooler lines to the right side of the engine block by the A/C compressor.