Help Diagnosing Weird Electrical Behavior

2017 SR5

I was hoping you guys could help me troubleshoot some odd electrical behavior in my truck tonight. It's late so I haven't even tried to look at it yet. Hoping to get some ideas that I can look at tomorrow, and hoping it can be explained by something very simple...like a battery or something!

Haven't experienced any problems until tonight. Tesla-style headunit didn't power up properly when starting truck. Turned off truck and restarted and headunit came up. Then noticed very slight headlight flickering while driving. Get to destination and while parking, headlights, headunit, and wireless charger all blink. Turn off truck and get out, the key FOB generates zero response and won't lock truck. Play around some, put my truck in accessory mode and power off, FOB then locks truck. Come back out to truck and key FOB doesn't work again. Had to manually unlock with key and reach over and manually unlock passenger door from inside because the power door unlock was unresponsive. Experience some faint headlight flickering on the way home. Key FOB locks and unlocks truck several times at home. Every engine startup during all this was snappy and powerful as usual.

Any ideas?

 

I m far from expert, but it sounds like major issue considering it involves so many things. It almost seems like a short, or something grounding out. You could disconnect headunit and see if problems still occur. I would check major electrical system connections, check for any loose fuses, maybe use scanner, and check for codes. It s probably no help to you, but if headunit, headlights, and keyfob/doorlocks are affected then one needs only to find the commonality of the three. ECU is the only thing I can think of, but like I said, I far from an expert. It could be something simple.

 

I’d be looking first at the body ground connection to the inner fender beside the battery, and the smaller cable(s) off of the positive battery post clamp that feed the fuse box. Any looseness or corrosion at either, or paint where the ground connects to the body.

 

Also check the actual battery terminal post clamps.
They are notorious for building up corrosion.
It is so thin it is hard to see.
Pull 'em off and clean them out..

 

Have you installed anything new recently?

 

test the battery. bad cells can cause weird stuff like this

 

You said the truck cranked fine during all of this so your battery is probably ok. It sounds like a loose connection issue to me. I would check the wires and connectors around the fuse box.

 

The last thing was the wireless console charger, but that was maybe 5 months ago. Zero indication of any electrical issues in the truck until last night.

Jotting everyone's suggestions down, will get out at some point today and begin diagnosing. Thanks for everyone's ideas so far.

 

Led lights can sometimes screw up fob functions, I would look close at battery, terminals, check voltage of alternator when running. Make sure chassis grounds are tight.

 

So start up is fine, good, helps to lead the troubleshooting. Beyond it just seeming fine I would grab a meter and measure its charge, it should be in the high 12v range. >12.4, preferably 12.6 or higher.

Once/if that occurs correctly, look to the alternator. An issue with maintaining electronic function could always have a source cause relative to the alternator. The battery primarily providing the amperage to start the engine, is then supplemented by the alternator to power the electronics.

Trace continuity between the alternator and its ground wire, end to end. It should not read open.

Start the truck and measure voltage out, should be between 14.2-14.5v could be higher or lower with margin of error, but in this case I would suspect it to be on the lower side.

See what that all looks like and let us know.

 

This has all the markings of a bad ground. Running a new ground from the body to the engine, and the engine to the frame won't hurt, and it might resolve the problem without spending a lot of time and money trying to find out where the existing ground is bad. A quick online search shows that there's a ground from the battery to the fender. If that's bad, the truck will start fine since the battery to engine ground is separate, but it will wreak havoc with electronics in and under the dash.

 

Are the batteries recharging completely?