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2005 Suburban Z71, 4wd, Flex Fuel
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Discussion Starter #1
I have been having issues since I bought this bad boy. First it was the rear diff, then it was the fuel pump, and the alternator. all of the calipers were trashed and the guy who had it before me abused and neglected this thing.

-Now my drivers side taillight won’t run the daytime running lights.

-The rear turn signals wont work (despite being brand new bulbs), and the side LED’s won’t light up either.

-abs module intermittently has a “C0268-pump motor short circuit”.

-the rear passenger window stopped working but has electricity running to it.

-butt heater doesn’t work on drivers seat but back heater does.

-all working windows are delayed when opening. As well as lock functions. And power mirrors only go down and left.

please someone help me get some useful information. Im tired of being told to junk it, and I’ve seen it run flawlessly. I fell in love with this truck and refuse to get rid of it.
 

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2005 Suburban Z71, 4wd, Flex Fuel
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7 Posts
Discussion Starter #2
truck sat for a year and a half while i was stationed in Japan so im not ruling out water, mice, and corrosion as possible issues. Also the belly is caked in mud because my buddy didn’t wash it off after taking it for a spin
 

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2005 Suburban Z71, 4wd, Flex Fuel
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Discussion Starter #3
Anyone have any ideas?
 

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First off, welcome back from overseas assignment.
Depending on your mechanical and electrical skill level, work on the easy ones first.
  • Battery, make sure it's fully charged. Clean both battery connections. Remove ground connections inside the engine bay, clean then reinstall.
  • check engine fluids, oil, coolant, power steering, transmission fluid condition (pinkish or black?)
  • 1-1/2 year old gas in the tank should not be that bad.
  • pull the fuel pump relay.
  • crank the engine until you get oil pressure.
-. If you have oil pressure, put the fuel pump relay back in, then try if you can get the engine started and running.
-. Then work on getting the tail lights and turn signals working.
-. Brakes, are they working?
-. Once you get it road worthy, you can take it to the self serve car wash so you can get it cleaned up. It's easier and nice to work on a clean truck.
- then work on one issue at a time.
 

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2005 Suburban Z71, 4wd, Flex Fuel
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7 Posts
Discussion Starter #5
First off, welcome back from overseas assignment.
Depending on your mechanical and electrical skill level, work on the easy ones first.
  • Battery, make sure it's fully charged. Clean both battery connections. Remove ground connections inside the engine bay, clean then reinstall.
  • check engine fluids, oil, coolant, power steering, transmission fluid condition (pinkish or black?)
  • 1-1/2 year old gas in the tank should not be that bad.
  • pull the fuel pump relay.
  • crank the engine until you get oil pressure.
-. If you have oil pressure, put the fuel pump relay back in, then try if you can get the engine started and running.
-. Then work on getting the tail lights and turn signals working.
-. Brakes, are they working?
-. Once you get it road worthy, you can take it to the self serve car wash so you can get it cleaned up. It's easier and nice to work on a clean truck.
- then work on one issue at a time.
Brand new battery coming in today, brake calipers have already been replaced and ive bled all the brakes, ive cleaned what i can with my pressure washer, fuel pump is all good now, and gas is brand new (drained, cleaned, and refilled), engine runs fine now and have taken it on a few test drives to be sure. Now im just struggling with the electrical issues. Do you have any ideas on what could be causing that one brake light not to work? Im assuming the window and lock delay is because of water damage in the driver switch assembly so im testing that out tonight.
 

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Guys with more electrical experience on this era trucks will surely help.
Glad you got it running
 
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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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3,361 Posts
Two things concerning the light to check.

The lighting ground is at the rear, driver side on the frame rail. The light circuit board could have a problem. Try swapping the housing from the passenger side. You won’t be able to install it, of course, but you may see if it fixes it.
 
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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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833 Posts
The light circuit board could have a problem.
I may be wrong, but I don't think the cat-eye trucks have circuit boards in the back light assemblies, anymore. I'm pretty sure it's independent sockets when the Silverado left the '99 OBS. My '00 Silverado has all the independent sockets. I'll look at the '03 when it returns this afternoon.
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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Good to know. Thanks for correcting me.
 
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2005 Suburban Z71, 4wd, Flex Fuel
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Discussion Starter #10
It has aftermarket tails in LED’s. They worked when I installed them but i can check if plugging it in the housing to the other socket works like you said Cowboy. And I’ve seen the ground and it doesn’t look insanely corroded, ill disconnect it clean it up, and apply some dielectric grease to the connection point on the frame. If its not those ill recheck the fuse diagram and cross reference to verify that the fuses are good again.

when i get home ill take a few pictures/video of the tail light issues (I don’t know about yall but im an extremely visual learner).
 

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If they are aftermarket assemblies, you should be able to just swap the left and the right assemblies. Leave the tailgate down and use it as a workbench to hold the units.

If the burnt out light goes to the other side you have a problem with the unit; if the problem stays on the same side, you have a wiring problem.
 

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2005 Suburban Z71, 4wd, Flex Fuel
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Discussion Starter #12
The drivers side tail light is fixed, but neither of the turn signals
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works. Hazards work in the front but not the back. I will be checking if a different type of bulb works (last ditch before checking wiring) and I verified that the fuses are not blown.
 

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2005 Suburban Z71, 4wd, Flex Fuel
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Discussion Starter #13
Is there a chance it could be the multifunction switch? The brake lights will blink instead of their corresponding turn signals.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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I'm thinking there's a wire crossed somewhere.
 

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A test light will be very useful in the absence of a wiring diagram.
Make a sketch of the connector pin out.
- Turn on the hazard switch
-- First find the ground pin.
  • Connect the test light clip to batt +
  • the pin that turns on the test light is the ground.
  • then connect the test light clip to the ground pin you just identified
  • with the test light, probe the pin which will flash the test light. No flashing light, means the connection is missing.

Do the same test for the park lights and reverse lights.
 
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Reactions: RayVoy

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The best test light(s) is an old taillight assembly, one that is known to work correctly.
 

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Yeah, I missed that one, he changed to aftermarket led tail light assembly.
If he still has the old tail light assemblies, you are correct @RayVoy
 
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