2002 Silverado Transmision Code P0700 P0875 P0843

My 2002 Silverado 2500 HD just started putting out codes: P0700, P0875,P0843. It has the 8100 engine and the truck has 42K on it. Truck runs fine and shifts great. Should I be concerned about these codes? Had the transfer case rebuilt last summer.

My 2002 Silverado 2500 HD just started putting out codes: P0700, P0875,P0843. It has the 8100 engine and the truck has 42K on it. Truck runs fine and shifts great. Should I be concerned about these codes? Had the transfer case rebuilt last summer.

you problem may be wiring issues..could also be from bad fluid..when did you replace the fluid and filter ? how do you use this vehicle ? does it haul tow heavy equiptment ?

this transmission requires proper maintanance. these codes indicate a delayed engagement..fluid pressure issues..dirty acidic fluid/stuck valves/poor electrical connections or wiring..


make sure you use the correct lastest updated fluid in this ..stay away from dexron III..

what was wrong with the transfercase that failed ? damaged clutch ?

My 2002 Silverado 2500 HD just started putting out codes: P0700, P0875,P0843. It has the 8100 engine and the truck has 42K on it. Truck runs fine and shifts great. Should I be concerned about these codes? Had the transfer case rebuilt last summer.
Hello monteheeren
Yes it needs checked out.
If setting codes there is a problem.
Allision transmission?
Code 700 is just check engine light on.
Code 875 is reverse pressure switch problem
Code 875 is presure switch C problem.
That may lock it in default/fail safe or 2 gear mode
Codes point to a pressure switch. (multi switch assembly)
Could be wiring or plug-in or switch or VCM computer ptoblems.
Are they present or history or past codes?
First codes needs cleared and see if they come back.
If they are present/hard codes they usually affect shifting.
If codes cleared with a scanner and return check pressure switch assembly and wiring and voltage feed.

Let us know how it goes

My 2002 Silverado 2500 HD just started putting out codes: P0700, P0875,P0843. It has the 8100 engine and the truck has 42K on it. Truck runs fine and shifts great. Should I be concerned about these codes? Had the transfer case rebuilt last summer.


I found this is which may help you with this allison tranny

The Allison 1000 Series™ uses two filters to maintain cleanliness of the Automatic Transmission Fluid (ATF). There is a 'spin-on' filter that is externally accessible and is intended to be changed at each ATF change (see owners manual for recommended change intervals). Current P/N for this filter is 29539579. Because this is a relatively 'high pressure' spin-on filter, it is important to tighten the filter one full turn after the gasket contacts the transmission case. Also, there is a removable magnet between the filter and the transmission housing; care needs to be taken that the magnet doesn't get 'thrown away' with the old filter if it happens to stick to the old filter. Beginning with MY03, GM Truck is recommending that the spin-on filter (filter only; not transmission fluid) initially be changed at 7,500 miles. Following that, the filter and fluid should be changed at the recommended intervals.
The other filter is inside the transmission oil pan, and is intended to be changed only in the event of an overhaul...

Thank you for the replays j Cat and MT-2500.
The truck is used to pull my car trailer a few times a year. Other than that, its used for light duty use. The transfer case was rebuilt because I had a problem with the Tcase not wanting to go into 4x4. Was in the shop 3 times for Tcase problems, but last time they totally rebuilt it.
I have cleared the check engine codes once. These codes are present codes.
Where is the pressure switch assembly?
I will try a new trans filter. I'm sure the truck has never had a new trans filter put on.

Thank you for the replays j Cat and MT-2500.
The truck is used to pull my car trailer a few times a year. Other than that, its used for light duty use. The transfer case was rebuilt because I had a problem with the Tcase not wanting to go into 4x4. Was in the shop 3 times for Tcase problems, but last time they totally rebuilt it.
I have cleared the check engine codes once. These codes are present codes.
Where is the pressure switch assembly?
I will try a new trans filter. I'm sure the truck has never had a new trans filter put on.

You are welcome.
Pressure switch assembly will be on valve body.
When you get the filter off you can see it good.
Good Luck and let us know how it goes.

Thank you for the replays j Cat and MT-2500.
The truck is used to pull my car trailer a few times a year. Other than that, its used for light duty use. The transfer case was rebuilt because I had a problem with the Tcase not wanting to go into 4x4. Was in the shop 3 times for Tcase problems, but last time they totally rebuilt it.
I have cleared the check engine codes once. These codes are present codes.
Where is the pressure switch assembly?
I will try a new trans filter. I'm sure the truck has never had a new trans filter put on.

you should have an external spin on filter as well as the internal filter ...the spin on is replaced at frequent intervals because it is traping smaller sized debris than the internal filter..if the spin on is restricted this can cause those codes..2003 GM with this transmission recommended replacing this filter at 7500mi.............

Just changed the external filter and cleared the codes.
So far so good. I'll keep you posted.

Just changed the external filter and cleared the codes.
So far so good. I'll keep you posted.

sounds good. cut open the old filter see how dirty it is. I would replace the fluid and filter again after a few thousand miles.

goodluck !

My codes are back again. :(
Codes: P0700, P0875, P0843.
These codes seem to appear after the truck has sat for a week or two.
Found this on the web:
http://www.justanswer.com/car/0mads-2001-gmc-2500hd-8-1l-allison.html

Any validity to this? After I clear the codes, and drive the truck, it is ok. No lights come on and it runs great. Maybe the solution is to just drive the truck more often!

My codes are back again. :(
Codes: P0700, P0875, P0843.
These codes seem to appear after the truck has sat for a week or two.
Found this on the web:
http://www.justanswer.com/car/0mads-2001-gmc-2500hd-8-1l-allison.html

Any validity to this? After I clear the codes, and drive the truck, it is ok. No lights come on and it runs great. Maybe the solution is to just drive the truck more often!

That one is a old TSB that has been superceed with this one.

03-07-30--011E puytbout April 2 - 2007

They have added some more stuff to the new on.

Have you dealer run the Vin for the latest TSB on it.

Looks like the transmission will have to be removed to do the things in TSB.


Before doing the TSB I would have a long Talk to your Dealer or transmission shop about it.
And do some proper testing to make sure the TSB covers your problem.

My codes are back again. :(
Codes: P0700, P0875, P0843.
These codes seem to appear after the truck has sat for a week or two.
Found this on the web:
http://www.justanswer.com/car/0mads-2001-gmc-2500hd-8-1l-allison.html

Any validity to this? After I clear the codes, and drive the truck, it is ok. No lights come on and it runs great. Maybe the solution is to just drive the truck more often!

this info you found would cause your problem . the torque converter if bleeding down fluid over time would give those codes on first running..then with regular useage its good...

on other gm transmissions if the transmission got very hot towing on a hot day after cooling down fluid can drain out of the converter causing a temporary loss of pressure and delayed engagement..

your torque converter check valve may need replacement ...with no external leaks and fluid level is correct ..

post back with the answer to this ..

Thank you for your reply j-Cat and MT-2500.
I'm going to talk to the dealer and my trans shop to see the next course of action. I will post back when I get the answer.
Still think this forum is awesome!