Weird electrical problems

[Jadalexm]

I posted a thread before about this but I’ve eliminated a bunch of possibilities so I’m trying again. I’ve got a drain on my battery that will kill it in about 12 hours. My gauges intermittently lose power. My security and battery messages are always on. Seat belt and airbag lights turn on and off. My obd port Cant be read by my Snapon scanner, I get a message that the voltage is too low even though it has enough power to turn the scanner on when I plug it in. I replaced the ecm and the bcm. No change. Replaced the radio and no change. I have a long list of fuses that keep power after everything is supposed to be asleep. And the front turn signal bulbs will flash sometimes after I turn the truck off and walk away. I’m a mechanic by trade and this is thoroughly stumping me. Any suggestions?

 

[swathdiver]

I posted a thread before about this but I’ve eliminated a bunch of possibilities so I’m trying again. I’ve got a drain on my battery that will kill it in about 12 hours. My gauges intermittently lose power. My security and battery messages are always on. Seat belt and airbag lights turn on and off. My obd port Cant be read by my Snapon scanner, I get a message that the voltage is too low even though it has enough power to turn the scanner on when I plug it in. I replaced the ecm and the bcm. No change. Replaced the radio and no change. I have a long list of fuses that keep power after everything is supposed to be asleep. And the front turn signal bulbs will flash sometimes after I turn the truck off and walk away. I’m a mechanic by trade and this is thoroughly stumping me. Any suggestions?

I would get the battery onto a charger or at full charge, hook up the Snap-On (bi-directional?) and go looking for parasitic drains. I am not very familiar with GMT800 options but maybe someone who is will chime in and tell you where to look.

 

[rdhogg]

I did see your original post , but I guess you checked all the grounding straps/cables. I know sometimes that can be a difficult thing to track down. Good luck , I hope more people chime in.

 

[PNWYukon]

What is the total draw amount?

Have you traced all the grounds and reseated them?

Have you taken the fuse box apart and looked at the underside?

Set up your meter and get the draw amperage then start unplugging fuses until the draw is eliminated. That should narrow the issue.

If you are really in New York, then corrosion is king.

 

[Jadalexm]

What is the total draw amount?

Have you traced all the grounds and reseated them?

Have you taken the fuse box apart and looked at the underside?

Set up your meter and get the draw amperage then start unplugging fuses until the draw is eliminated. That should narrow the issue.

If you are really in New York, then corrosion is king.

I haven’t checked the total draw amount. I took the fuse box apart and everything was mint underneath. The truck came up from Florida a couple weeks before I bought it and has zero rust or corrosion anywhere. Next thing I’m going to do is try and reseat the grounds. But the issue started when lightning struck a wire that was near the truck when it was in Florida. And no mechanic the guy took it to could figure it out. I thought it was worth the smoking deal I got it for but it’s proving to be more difficult than I thought.

 

[Doubeleive]

unplug the instrument cluster and see if the draw goes away, the clusters can go bad and your description sounds like it is the issue no reason for those lights to be on all the time, neither should it be loosing gauge readings. the cluster is not required to be connected but it will cause a communication error code over time.

 

[exp500]

Are all the computer plugs and pins clean?( BCM/ECM/Etc). Water would be a clue.
I agree with find the load and track that system back to battery. Could be as simple as a hot wire grounding on some dash structure too.

 

[Fless]

You really need to see what the total draw is. There are many good parasitic draw YouTubes, Eric O at South Main Auto has several. It's best to use the voltage drop method on the fuse test points, instead of pulling fuses; that way you're not waking up modules by reinstalling the fuses. If you need a link to the voltage drop charts tag me in a post or PM me.



If you have the Auto HVAC control it can take 3-5 hours for it to fully shut down. Normal and spec. But it should draw only 40-60mA when awake.

I had an intermittent parasitic draw on my NBS; ended up installing a shunt inline with the negative battery cable, and put the meter where I could monitor the draw any time. Left it there for a few months while I monitored the draw every time I shut off the truck. At a minimum you need a meter that is rated for the next highest Amp value that your alternator puts out. I went overboard and got the 300A one because I didn't know that at the time. A 200A model would do fine if you have a standard alternator.
https://www.amazon.com/gp/product/B0828HTM6F/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

After fixing the draw I uninstalled the shunt and now I just use a somewhat special clamp meter that reads in mA. Link below. Unlike many clamps, it reads DC current in the mA range, but the jaws allow only a 1/2" cable diameter. Somewhat pricey, but it's perfect for my negative battery cable.


https://www.ebay.com/itm/352176994690

 

[Teamiez]

I haven’t checked the total draw amount. I took the fuse box apart and everything was mint underneath. The truck came up from Florida a couple weeks before I bought it and has zero rust or corrosion anywhere. Next thing I’m going to do is try and reseat the grounds. But the issue started when lightning struck a wire that was near the truck when it was in Florida. And no mechanic the guy took it to could figure it out. I thought it was worth the smoking deal I got it for but it’s proving to be more difficult than I thought.

My friend had a Subaru that was struck by lightning...I was surprised it wasn’t totaled out they replaced damn near every computer / electrical component. On top of that hopefully it isn’t a cleaned up flood truck.

 

[retiredsparky]

Bazillion volts (electronic term) of lightening can fry anything in our vehicles. Lightening has so much power that anything with metal, or carbon (tires, wire insulation, plastic, etc) can conduct some of the electricity that is present around the area of a strike. I have seen and repaired damage by lightening and high voltage AC power (12,500V). Metal can be vaporized, welded; insulation can be fried, resulting in improper connections between adjacent conductors.
I would replace the dash module as a start. That may not cure the problems, but since it is a printed circuit board, it is a possibility.
When discussing lightening damage, it is important to remember that there are tiny modules and sensors that may have printed circuit boards or miniature components scattered throughout modern vehicles. They are connected to each other by both communication wiring, power wiring, sensor wiring and control wiring.
The battery could have been damaged in a weird way. Try substituting any automotive battery to see if symptoms change before you buy a new battery. GM products are very sensitive to batteries that have internal damage from any cause (age, sulfation, lightening, high impedance internal connections). I have had two GM vehicles that had unexplainable symptoms fixed by replacing the battery.
Unfortunately, it is possible that some harnesses have been damaged, resulting in improper connections between adjacent conductors.
Another possibility is a damaged alternator-take it to a qualified automotive electrical shop for testing.
Bottom line, any electrical or electronic part or wire can be damaged by a lightening strike. Good luck.