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03 Avalanche 1500 4WD with electrical/starting problems

Brand0lin3

New Member
Joined
May 23, 2021
Messages
4
Hello All,
Hoping for some help so that we don't have to invest more in the vehicle than it's worth! Not electrical experts here, nor pro mechanics...


The problem started when a light on the dash stated that the battery is not charging. Made it to a parts store to test the battery, and it tested bad. Replaced the battery, but it wouldn't start, just a rapid clicking sound.


The only know problem prior to this issue was that the oil pressure guage was flaky.


We then replaced alternator, as it also tested bad with a bench test. Cleaned the connections on wires to battery and new alternator.


Truck will now start when jumped, but whether it stays on is intermittent. At first, had to hold the gas pedal to stay on. Then, made sure lights and all systems were off, and it would stay on at a low idle. However, pressing on the gas after this killed it.


We're getting 12ish volts on the battery when connected to the USB battery starter, and 13-14V when running. But it still won't start on its own. The battery guage on the dash seems to be fairly consistent to testing with a multimeter, and not showing anything crazy until it dies. Then, we seem to lose all power, and interior lights and other systems (while off) slowly come back up to normal.


We're going to replace/test almost all of the fuses next. But if that doesn't solve it, we're stumped on where to go next.


Ideas that I've read so far while looking through various forums include: ignition switch, starter, fuses, battery wires, ground wires, a tune up, throttle position sensor, throttle plate, fuel pressure regulator, EGR valve, MAPS sensor, temperature sensor, and various other wiring shorts.


Given the expense it would take to try all of these, you can see why we need help in narrowing it down! Thank you for reading!
 
There are several ground points on these trucks.

There are several discussions on this forum as to their various locations.

Depending on where you live, some of these grounds are known to corrode and cause all kinds of electrical problems.

Perhaps researching the posts in this forum concerning grounds would be a good place to start.
 
We live in Ohio, so corrosion is completely possible! Thanks so much for the direction!

(There were no fuse issues, btw)
 
Good Mechanic who can look and trouble shoot...

For your truck too many things it could be for a FORUM repair.

Check wires, check for battery drain

Check for any electrical mods added to truck
 
Thank you for the advice. No mods on the truck.

I found yesterday that there are several highly rated mechanics in our area, fortunately. I have always found good mechanics hard to find, but it's been a long time since I've looked.

We're going to check the ground wires and battery drain, and then consult with an expert. Fingers crossed!

Thanks all!
 
I fought electrical gremlins for years and started the same way you did with my 04. The icing on the cake for me ended up being the battery cables. After thoroughly cleaning all my grounds and still having voltage problems, I replaced my positive and negative battery cables. I ended up finding corrosion between the power box and battery, as well as by the starter. Make sure you search ground locations here and address those first before you spend the money on battery cables. Some people prefer the big 3 upgrade and build their own battery cables bigger than stock.
 
Update on the truck, we ended up finding a pretty good mechanic and getting it towed there.

The problem they found was that the brand new battery was actually faulty, which then caused the throttle body sensor to malfunction. New battery (warranty replacement), fixed the sensor, and cleaned the throttle body for $300.
 
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