Strange problem with the electrical system

Hey everyone,

I'm having an electrical problem that I'm having a difficult time diagnosing. Came out to my truck the other night, and it wouldn't start. It was doing this:

https://www.youtube.com/watch?v=xfy-vkMkpM4

In that video, I'm trying to start the car, and it looks like the ECU keeps tripping and resetting.

I get some jumper cables, and get the car started. Starts right up. The voltage on the scan gauge is jumping around all over the place:

https://www.youtube.com/watch?v=nV25BhdCty4

In this video, the engine is just idling in neutral. Notice the voltage.

I decide to start driving, thinking the battery just needs to be charged under load. The voltage is still hopping around:

https://www.youtube.com/watch?v=weFZJbeVxII

Usually, the voltage is 14.1 or 14.2, rock steady.

After about 30 minutes of driving, I park the car, turn it off, and try to restart it immediately.

https://www.youtube.com/watch?v=AEjbPB5uqVs

Same thing as above.

Truck is a 2005 V6 4.0L 4X4.
Battery is about 5 months old.
Scangauge II is the only modification to the vehicle.

Does this appear to be a battery problem, an alternator problem, or a regulator/rectifier problem (inside the alternator, if I understand this correctly)?

 

I would start by looking if the main ground is good in place

 

Yup the ground my guess

 

Loose battery terminals.

 

Loose terminals at battery.

 

Check battery terminals and if they are good have the battery load tested at the auto parts store. ( usually free ).

 

Check the cables as they can rot inside the insulation. Clean ALL connections you can - Ground at Bat and Engine. Grounding connections to Vehicle/straps to chassis, Both ends of the Pos cable.

Also , Most shops will test your Battery an Alt for free. Take advantage of it, The more things you check and test the closer you get to the fix. (The last fix is right fix! )

 

This. Seen something close to this and it turned out the cable from the Alt to battery was bad at one of the ends.

 

I would unplug the scanguage from the OBDII port first. Then disconnect neg terminal and reconnect. See if it starts and returns to normal. Sometimes, Scanguage and Ultraguage can miscommunicate with the ECU and cause weird issues like that - its rare, but can happen. If that is it, go to scanguage and look at their manual. There is usually something you can do to the programming that will fix this problem.