2000 Silverado 4wd light

[Mod_12]

I have a 2000 Silverado Ext Cab LS 5.3 4x4 z71 and the service 4wd light comes on the dash after driving about 3 miles or so. I took it to the dearlership today and had them run for errors and nothing came up. All of the push button dash lights are on and working. Any Ideas what could be causing this? Also I need to buy 2 cat converters for this truck and looking to find the correct ones without paying dealer prices. Thanks

[ukrkoz]

really? all the diagnostic done by dealer and no ideas? :sarcasm1:

swap your automatic transfer switch. those are notorious to break down at about 60-70K miles. around 60 bucks and 5 minute job.

[MT-2500]

Originally Posted by Mod_12

I have a 2000 Silverado Ext Cab LS 5.3 4x4 z71 and the service 4wd light comes on the dash after driving about 3 miles or so. I took it to the dearlership today and had them run for errors and nothing came up. All of the push button dash lights are on and working. Any Ideas what could be causing this? Also I need to buy 2 cat converters for this truck and looking to find the correct ones without paying dealer prices. Thanks

What is the mileage on it?
8 year or 80 K emmision warranty on cats.
What tarnsfer case?
Has transfer case ever been serviced?

If that is the best you dealer can do ask for your money back and find
Find another dealer or a good repair shopthat can find the problem?

Why does it need cats?

Dealer cats or a good parts house OEM type direct fit cat set up is the way to go but not cheap.

Make sure cats are bad and if they are find out what is causing them to go bad.

[j cAT]

Originally Posted by Mod_12

I have a 2000 Silverado Ext Cab LS 5.3 4x4 z71 and the service 4wd light comes on the dash after driving about 3 miles or so. I took it to the dearlership today and had them run for errors and nothing came up. All of the push button dash lights are on and working. Any Ideas what could be causing this? Also I need to buy 2 cat converters for this truck and looking to find the correct ones without paying dealer prices. Thanks

the 4wd dash select switch on my 2000 as well as many others ,, had bad solder joints on the switch pins/circuit board...I resoldered the pins after they were indeed poorly soldered....

this occured around the 40,ooomi point just after warrantee ran out...this should have been a recall...

same exact symptoms as you run a few miles and the 4wd lt is on..

when removing switch no tools required it is very easy,,,dealer will charge well over 100.oo to replace...

because this is intermittent the vehicle must not be shut down after the light comes on,,then the code should be there ...but the code will indicate a communication error...depending whats soldered bad...

the dealer could just shotgun this and charge you for componets not required...

[Mod_12]

truck has 135,000 miles on it. I have not serviced the transfer case in the 3 yrs I owned it. How do I know what one I have? I bought 2 quarts of the TRAC fluid from the dealership. The only reason thinking the Cats are bad is that the truck has lost power and piss pour gas milage 12-13mpg was at 18mpg when I purchased it. I have replaced everything I can think of like plugs, plug wires,air filer, all 4 o2 GM sensors, pressure regulator. EGT valve,fuel filter, I the clean mass air and throttle body bi-weekly. Today I went to a local mechanic (worked for GM dealership) that I have known for 35 years and he said he has had 3 trucks in the last 3 months with the same problem. Once he changed out the Cats they ran 100% better. But he wasn't sure why they were getting clogged. Any other Ideas?

[MT-2500]

Originally Posted by Mod_12

truck has 135,000 miles on it. I have not serviced the transfer case in the 3 yrs I owned it. How do I know what one I have? I bought 2 quarts of the TRAC fluid from the dealership. The only reason thinking the Cats are bad is that the truck has lost power and piss pour gas milage 12-13mpg was at 18mpg when I purchased it. I have replaced everything I can think of like plugs, plug wires,air filer, all 4 o2 GM sensors, pressure regulator. EGT valve,fuel filter, I the clean mass air and throttle body bi-weekly. Today I went to a local mechanic (worked for GM dealership) that I have known for 35 years and he said he has had 3 trucks in the last 3 months with the same problem. Once he changed out the Cats they ran 100% better. But he wasn't sure why they were getting clogged. Any other Ideas?

Transfer case ID tag is on rear of transfer case.

On the cats proper testing before replacing.

What is engine vacuum at idle and at 2K rpm?

If cats are bad there is usuallay a reason for them going bad.

[ukrkoz]

ahm, here's a novel idea:

did you try to read codes off ecm?

go to any Midas, get your truck up on the lift and they will blow 2 holes, one pre-cat and one post cat, to check on air flow. if it's same - your cat is still meowing fine. it's free of charge usually.

[j cAT]

Originally Posted by Mod_12

truck has 135,000 miles on it. I have not serviced the transfer case in the 3 yrs I owned it. How do I know what one I have? I bought 2 quarts of the TRAC fluid from the dealership. The only reason thinking the Cats are bad is that the truck has lost power and piss pour gas milage 12-13mpg was at 18mpg when I purchased it. I have replaced everything I can think of like plugs, plug wires,air filer, all 4 o2 GM sensors, pressure regulator. EGT valve,fuel filter, I the clean mass air and throttle body bi-weekly. Today I went to a local mechanic (worked for GM dealership) that I have known for 35 years and he said he has had 3 trucks in the last 3 months with the same problem. Once he changed out the Cats they ran 100% better. But he wasn't sure why they were getting clogged. Any other Ideas?

the cat restriction is a very real possible failure, with your lost power and MPG...checking for restriction should be done....before replacing...
the O2 sensors need replacing at the 100,ooomi point,,,these sensors the upstream ones can very well damage the cat.If not replaced at that mileage..also an intake manifold/antifreeze leak into the combustion chamber will damage the O2 and then the cats...

the muffler may also be restricted ....

when you install the trac II transfercase fluid you may need 2.25qts..and also need a pump that fits in a qt bottle..to fill..

always remove the top fill plug first ...use light torque to secure these plugs coat threads with thread sealant ,,just a light coating..this will ensure a good seal and removal ease...

the fluid removed should be a blue color ,,the darker the fluid the more you should consider a sooner replacement interval..

[Mork]

Mine did this also. Check the fluid level in the front differential. Top it up. Mine was down and this turned off the warning.

Jim

[Mod_12]

OK today took to a friend shop and did 4 hrs of diagnostics on the truck for the rough Idle, power loss and gas guzzling.

1- vacuum pressure.. 15-20 pressure
2- Cats check out fine...no back pressure.
3- fuel pressure...50-55 psi and idle and 45 psi when driving
4- scan for codes none
5- after idling 5 Min's with scanner in we had mis-fires on 3-5.
6- moved the coil packs around nothing changed.
7- idling it started to mis-fire on all cylinders with some cylinders as high as 3 times. like 3-5 then 1-8 ,2-6 , etc...
8- We think we narrowed it down to cam sensor or fuel pump but fuel pump seems to be working within the tolerances of the manual.

truck has 133,000 on it so I am gonna changed the fuel pump since it time for one and hope that cures it.
Has had injectors cleaned, plugs and wires, EGR valve, air cleaner, PCV, fuel filter done

[MT-2500]

Fuel pressure is to low .
Specs are 55/62.
You need to see 58-60 running on road.
Need engine vacuum reading at idle and at 2K rpm to rule out cat restriction.

Maf sensor or low fuel pressure will also cause missfire.

[Mod_12]

vacuum was 15 at idle and somewhere between 20-25. Can't remember what he said it went up to. I seen the needle move alot as soon as i took it to 2000rpm's. I couldn't clearly see gauge from my vantage point.

[MT-2500]

That is good.
On fuel pressure 5.3 have a lot of fuel pressure regulator problems.
If you replace the fuel fump go with a Delphi fuel fump.
Airtex and after market do not cut the mustard .
Good Luck

[MT-2500]

You fuel pressure is to low.
Specs on it is 55/62 lbs of pressure
Here is some guide lines of fuel pressure checking.

Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 55-66 fuel pressure.
Cold start should be 55/62 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 55/62 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
If pressure does not come up with return line pinched or blocked off.
Go to fuel filter and hook a gauge direct to a line at fuel filter.
Pressure should come up to 75 or more and will hold after fuel pump is turned off.
If it leaks down there after fuel pump is turned off it is LEAKING BACK THREW PUMP CHECK VALVE OR PUMP MODULE LINES.
Post back your fuel pressure readings.
MT

[j cAT]

Originally Posted by Mod_12

OK today took to a friend shop and did 4 hrs of diagnostics on the truck for the rough Idle, power loss and gas guzzling.

1- vacuum pressure.. 15-20 pressure
2- Cats check out fine...no back pressure.
3- fuel pressure...50-55 psi and idle and 45 psi when driving
4- scan for codes none
5- after idling 5 Min's with scanner in we had mis-fires on 3-5.
6- moved the coil packs around nothing changed.
7- idling it started to mis-fire on all cylinders with some cylinders as high as 3 times. like 3-5 then 1-8 ,2-6 , etc...
8- We think we narrowed it down to cam sensor or fuel pump but fuel pump seems to be working within the tolerances of the manual.

truck has 133,000 on it so I am gonna changed the fuel pump since it time for one and hope that cures it.
Has had injectors cleaned, plugs and wires, EGR valve, air cleaner, PCV, fuel filter done

the fuel pressure OEM GM spec min is 53psi.....60psi is good with new pump.... 53 psi and lower pump needs replacing or the ground at frame rail next to the fuel tank is not secure/clean or possible fuel pump relay...

lower fuel pressures cause random miss fires...as stated many times only use delphi pump....

I don't know what manual you refer to but this 2000 silverado requires the stated pressure ...........45 psi and it runs is surprising...

replace the relay/filter if you do have to replace the pump..

this engine has a cam and crank shaft sensor....these seldom have problems though some have had connector issues...