Just thought I'd share an odd fix to a somewhat common issue on this generation of F-150's.

About a month ago, I had a service charging system light come on, then go off after 10 seconds. I found it odd, the truck didn't die though. Codes were P065B, P0620, P0626. All generator control circuit codes; 65b for range performance, 620 showed no description, and 626 for terminal circuit high.

Attempt 1) To cross my T's and dot my i's, I load tested the battery, which was original from 2015 when the truck was built, and it spit out 600/610 CCA and was able to hold a charge no problem. Did voltage drops from post to terminal, post to alternator, terminal to alternator, negative terminal to chassis, negative post to chassis, post to alternator case, so on and so forth. At idle 13.0V~. Just for kicks, I replaced the battery with a Motomaster 730CCA 4 yr warranty battery. After the ECU did its drive cycle, the message came back along with the codes. I allowed the truck to sit overnight and later reset the BMS via forscan just to be sure.

To make sure the wiring wasn't screwed, I took it to my mechanic, and explained everything and asked them to inspect and advise. They figured that the regulator was taking a crap, and told me to replace it along with the pigtail. I found a reman unit on Rockauto for $260 CDN shipped to my door, which compared to local mechanics pricing, was a bargain. I replaced it. 2 days later, message comes back. Keep in mind the truck has never died on me at all.

Now I'm pissed. I take the truck to my buddy's work and steal his scanner for a bit. I start the truck in engineering mode in the cluster and scroll to the voltage option, hook it up and go into the generator monitoring section. I pull the commanded voltage and the output voltage. Commanding voltage is 14.6, output voltage 14.6, but the dash says 13.2(iirc) to 13.8 and rapidly changing. At this point, I came to the conclusion that my issue has to be in the ECU pigtail for the alternator.

Bought a new Dorman pigtail, got my mechanic to inspect the harness down the line and replace the connector. He didn't find anything but still put the new connector on and it seems to have fixed the issue. My guess is that there must have been some barely visible/noticeable corrosion on the connector, as I do live in the salt belt.

Thought I'd share to potentially help prevent someone else from pulling their hair out like I was.

Cheers all, hoped this helped/was informative!

 

Looks like you may have found the problem. I thought, from the P-codes you posted that the ECU was not communicating properly with the reman alternator you installed. A faulty pigtail could cause that, I expect.

It might help explain things, and make your thread a bit more valuable, if you were to post that image of the P-codes you'd posted in the Honda forum here too. What was the charging voltage at the battery terminals, when you read the voltages you describe above? As I told you, 14.6V at the battery means it is being charged.

- Jack

 

Prior to alternator replacement, terminal voltage was, if i remember correctly, high 12's low 13's, after alternator replacement but before terminal replacement, was at 14.3-14.6. I have yet to re-test the charging voltage, but I don't even want to pop the hood on this thing because of how much of a headache this stupid issue was. Currently there's no DTC's set, be it pending or confirmed. Mind you, the truck did come from the Canadian Province of Newfoundland, and basically the entire province is on the east coast and it shows. The truck isn't horrible in terms of corrosion, but my dad's (and probably most other) 2016 f-150 has faired better cosmetically in terms of the undercarriage/ frame. That's why I'm leaning more towards the corrosion side of things. Whatever it was, I could care less now because it's fixed and over with.