More Electrical Fun (not!)

[S33k3r]

So we got a ground repaired several weeks ago. Then we get to the Tuesday before Thanksgiving, and power windows, power door locks, heated seats, power to the cluster, and the OBDII port all go out. Due to illness, I just got it into the shop today. We'll see what my mechanic says.

Since the OBD port isn't working, my nice scanner was silent; we did confirm it was not the scanner because we used it on a different suburban and then on my silverado. We also believe we cleared the BCM, because I have a spare, connected it and... Nothing changed... Even the OEM DVD player would power on, and seemed to be communicating on the internal bus. So I think we simply have a short somewhere, but I do not know where... It's killing the battery, though -- 1 - 2 days and the battery is dead.

Anyway, I post here in case someone else suffers a similar fate. Once cause and fix are determined, I'll post here so it'll be easier on someone else.

 

[Fless]

Since the battery is draining there may be a parasitic draw, and that diag could lead to the cause of the electrical outage.

 

[S33k3r]

Since the battery is draining there may be a parasitic draw, and that diag could lead to the cause of the electrical outage.

Oh! Absolutely. I just could not think of more things to do besides a meter and going wire by wire, which I know I don't have the time to do, and usually do not have the patience. Plus it is my wife's car, and it has been down more than up for the past month or two. I just keep blaming her for driving through wheel-well deep water when Dallas flooded a couple of months back (1000 year rainfall). My mechanic has repeatedly told me it was not a flood issue, though, so... And we aren't in a position yet to buy a new vehicle with all the stuff our GMT800s have in them. Else I would have bought that new Hummer...

 

[Fless]

Well, the initial part of the diag is to test the voltage drop across each minifuse (using the embedded test points) to see if one of those circuits has current flowing while the truck is fast asleep. Would take 10 minutes and no circuit interruptions. Of course, if that shows nothing, then a deeper dive into the other circuits is warranted and that could take some time and more effort.

 

[MassHoe04]

It starts, runs and drives OK? It is just the accessories/windows/cluster that are not responding?

Have you probed the tops of the fuses to see if any fuses are blown out?
I know you don't want to go wire by wire, but checking on the test points on top of the fuses is easy and fast to do.

 

[Moosemoon]

Well, the initial part of the diag is to test the voltage drop across each minifuse (using the embedded test points) to see if one of those circuits has current flowing while the truck is fast asleep. Would take 10 minutes and no circuit interruptions. Of course, if that shows nothing, then a deeper dive into the other circuits is warranted and that could take some time and more effort.

Where are the embedded test points?

 

[Fless]

Where are the embedded test points?

On standard blade fuses:



Once you read the voltage drop (if there is any, that circuit will have current draw) you'll need to convert the mV reading to amps using a chart like I've attached or pull it from this link: https://m.roadkillcustoms.com/wp-content/technical-pdf/Mini Fuse Voltage Drop Chart.pdf
This one is for mini fuses but they can be found for other sizes. You can't measure the JCase square fuses very easily.

Google "fuse voltage drop chart" for other styles of fuses