PCM Code 28

[skunk0526]

code keeps popping up and have no idea where to start for this part:

transmission range pressure switch assembly.
28 - 3rd gear switch was closed or grounded for 10 seconds when vehicle was in 4th gear, or 3rd or 4th gear switch was open when engine was first started.

mistook this code for oil pressure switch (which needed to be changed anyway)

Cleared code by disconnecting negative on batt for 30 seconds.

Still popping up. has to be trans switch.

Where do i start?

[skunk0526]

got as far as finding out that the pressure switch assembly is made up of 5 switches mounted on the valve body.

My question is where is the valve body?

[MadMikeZ28]

The valve body is inside the transmission pan. Remove the pan and you will see shift solenoids and that switch. It is a fairly wide flat shape.
Before replacing that switch though, go to an Autozone and see if they would be kind enough to print out an Alldata diagnostic chart to test first. You will end up taking the pan off to do test anyway but may save you money from buying a switch. Also unplug the wires from the side of the tranny on the outside and make sure they are all fine and use a mirror to look in the plug on the tranny for dirt and what nots.

[skunk0526]

Quote: Originally Posted by MadMikeZ28

The valve body is inside the transmission pan. Remove the pan and you will see shift solenoids and that switch. It is a fairly wide flat shape.
Before replacing that switch though, go to an Autozone and see if they would be kind enough to print out an Alldata diagnostic chart to test first. You will end up taking the pan off to do test anyway but may save you money from buying a switch. Also unplug the wires from the side of the tranny on the outside and make sure they are all fine and use a mirror to look in the plug on the tranny for dirt and what nots.

Awesome! Thanks for the info!

So, the pan has to be off for them to do the test? I would be taking off the pan in their lot? Or am i just misunderstanding? The AZ's around here are not repair centers.

Hopefully get it tested tonight. This same code popped up about a year ago and I went to a tranny shop. He charged me 160 and i swear he did nothing but clear the code, because it was doing the same thing 2 weeks later.

Thanks again Mike!

[jtcfanof3]

If I get a chance tomorrow, I can pull up the AllData info for ya and paste it here....... unless Mike brings it up for ya before then.
Is this the truck:
1993 s-10 4x4 Blazer 4 door Tahoe Package 4.3l

[MadMikeZ28]

You don't want to pull the pan at AZ. They do not service cars here either but they do market Alldata. The one here I used to do business with when i had my shop could get print out info from Alldata to take home that would help people fix theri autos. Don't know if they all do that. May just be a few or the ones that have serve shops with comercial accounts.

If JTC could do that I'll give him some slack on stocking up the salami sandwiches and Dr. pepper.

[jtcfanof3]

http://library.alldatapro.com/alldat...50364/41877253
Link probably wont work, Ive saved it onto my flash drive so I will upload it when I get home if it does not work.

[skunk0526]

Thanks JTCFAN. I stopped at AZ last night and the jerk said they don't give all data sheets and that part was a dealer only item. Any suggestions on finding one without the dealer prices?

He couldnt even give me a part #.
At least with that, i would have somewhere to start.
Gonna try calling some tranny shops in the area to see if they can help.

Gonna try do diagnose (again) tonight.

[MadMikeZ28]

I replaced one a while back and the shop cost was about $58.00 for it. I just looked at my paper work but there was no part number damn it.
In fact my switch was not bad, it was dirt in the connection that I could not see (thats why I said use a mirror in the plug). But unfortunatly I left that good switch I replaced at the shop with my brother and I'm sure its long but gone.
Its all JTC's fault!

[jtcfanof3]

LOL Mike........
Awesome, the AllData link works!! Tell me if that helps, that is the diagnosis on the code 28.

[skunk0526]

Appreciate the sheet, but i don't have a reader. And even if i did. it would take me days to decipher how to apply the diagnostic sheet.
I'm going to drop the pan this weekend, clean the filter, check for damage/ dirt to switches as Mike recommended. After that, i'll put the effort back into finding this switch assembly. I swear it's like trying to contact Bin Laden to get someone to even know what your talking about. Especially when i can give them the exact tranny.
My bigger problem right now is getting the loot for new rotors/pads/calipers.
A bunch of BS all at once. Thats a blazer. Wouldn't have it any other way.

[MadMikeZ28]

Found this,
http://www.bulkpart.com/Merchant2/me...roduct_Count=7
Cheaper than what I paid!..... MF'er!!!!

[skunk0526]

Holy Crap! you're good!

Judging by the cover, are you sure its not a 4L60?
I'm just going by the gm good wrench pan shape transmission guide.

http://www.goodwrench.com/_res/pdf/T...tification.pdf

Can't tell a size ratio from this chart. You would know better than i.

So, thats the part i'm lookin' for? "Transmission range pressure switch" as the diagnostic calls it? Or is it in this whole bank of manifold switches.

You guys amaze me. really. been rackin' my brain on this, and mike finds it in hours?

[MadMikeZ28]

The 700R4, 4L60 and 4L60E all have the square 16 bolt pan. The year of your truck would be an E model and you would not get that code with a non-electric tranny.

And it only took a few minutes to find that switch searching the web. It took me hours too think of looking for it!

[TrYiN2LaYaDiMe]

i hate transmissions why they need to be so difficult. at least ur getting a code dude my trans is ****ed and i get no code. but here is a picture from that link jc posted

[skunk0526]

Quote: Originally Posted by skunk0526

got as far as finding out that the pressure switch assembly is made up of 5 switches mounted on the valve body.

My question is where is the valve body?

It was my understanding that this bank of switches is mounted directly onto the valve body. Case in point:

(Valve Body, 4L60E (4 Switch) (Aluminum) (4 Switch Not Counting The Manifold Pressure Switch) 1992-94)

Manifold pressure switch would be 5 and a switch of its own. Transmission range pressure switch would be one of the 4 mounted on the valve body. No?

Here's where i found that. not trying to be a smart ass . Just wanna be sure.

Click on valve body part # for info:
https://www.wittrans.com/Schematic.a...0E&Schematic=6

[MadMikeZ28]

I am not sure what you are getting at. There are shift solenoids which are not pressure swicthes.

[skunk0526]

since I've never studied a valve body up close, i thought there were replaceable switches on there. So it's 1 piece w/ no replaceable parts.

The only time I've seen one, its been in a b/w representation.

Looks like i'm pulling the pan & cleaning/ looking for dirt next.

[MadMikeZ28]

The swicthes are replaceable. The link I posted was on the pressure swicth. the silve spacers are where the bolts go through and the red spots are where the pressures are monitored. Even the shift solenoids come off the valve body, Just like in the link you posted.

[TrYiN2LaYaDiMe]

http://www.youtube.com/watch?v=1cjli1HKPCo

[TrYiN2LaYaDiMe]

ok i failed at uploading this to view but its a break down of a 4l60e valve body check out his other videos on removal and installation of valve body

[MadMikeZ28]

There is no reason on need to remove the valve body to remove or replace the pressure switch or any of the solenoids. You go through the trouble of removing the valve body and you will end up saying "Oh Fvck" afterwards.

[skunk0526]

Quote: Originally Posted by MadMikeZ28

There is no reason on need to remove the valve body to remove or replace the pressure switch or any of the solenoids. You go through the trouble of removing the valve body and you will end up saying "Oh Fvck" afterwards.

NO! not doing that. dropped the pan. of course cross member in the way. Pictures to follow with a couple other questions to follow. Considering re-routing exhaust when i have to do this next time. hanging it up this evening, but looking for suggestions in the pics that will follow.

[skunk0526]

#1 I would assume i have to jack the tranny up to remove cross member



#2 Is there any other place to drain the tranny other than the pan? Chilton's is very vague on the tranny they have instructions for. and i see no drain plugs.

Just want to be sure I'm completely draining it.

it doesn't smell burnt or colored dark.

#3 What is this sensor/plug? (tried to get as much parts in the pic as i could to identify it. I'm having trouble identifying parts)

[skunk0526]

Cross brace misery. not in the mood tonight.

[TrYiN2LaYaDiMe]

lean the pan forward (away from u) there is still fluid in the pan i can assure you of that. and no there isnt a drain plug.


and the video was just showing u what is in the valve body not intending for u to take it out. just purely informational for ur knowledge.

[MadMikeZ28]

I don't think the pan will tilt forward. If I remember right the deep part hits the exhaust so you have too tilt towards the back. Gotta put a jack in the back and lift the tranny off the mount and then you should be able to work the pan out.
And there will still be fluid in it. Thats why there are real wide drain pans for this kind of work.

[TrYiN2LaYaDiMe]

we tilted mine the other day but i have a 4x4 Z71 so the area is alot different.

[TrYiN2LaYaDiMe]

since i got sorta yelled at for the video here is a picture that helped me alot when i got into the pan. hope this helps u. im not sure how familiar u are of the valve body.

[skunk0526]

thanks for all the help, pics & suggestions. Unfortunatly the pan is i still wedged in place.

I tried jacking the tranny a bit, and didnt like the noises i was hearing. didnt want to snap anything. I'm being over cautious as you can tell since i cant afford any additional repairs after this (may) get fixed. how much give will it have when jacking the tranny? I gotta get this pan off soon to just diagnose what i need to do. I'm really frustrated.

Would disconnecting exhaust drop the pipe enough to slide the pan out? moving the cross member is a no go since i cant break the bolts.

running out of time. need my ride!

[skunk0526]

Quote: Originally Posted by TrYiN2LaYaDiMe

since i got sorta yelled at for the video here is a picture that helped me alot when i got into the pan. hope this helps u. im not sure how familiar u are of the valve body.

I'm assuming the Manifold Pressure Switch would be located under the manual valve position cover? its the only thing that remotely looks the same shape.

IF i ever get to this step!

[TrYiN2LaYaDiMe]

the motor/trans should move enough with out breaking since the only thing holding it would be the motor mounts (to my knowledge) thats if u have the trans unbolted from the crossmemeber. just take a break man sit back and think ull figure it out man ur just getting mad and working mad wont fix it trust me i know lol.

[TrYiN2LaYaDiMe]

you'll get to it man just chill out like i said. and yes i would assume so. watch the video of the valve body tear down thats why i posted it.

[skunk0526]

It's unbolted from the crossmember but there are support rods on either side of tranny. should i take these out? how exactly is too much lift of the tranny?

This seems the only place to be able to lift it. (where the stain is)

[TrYiN2LaYaDiMe]

i dont see any rods but if they can come out take them out but becareful.

[jtcfanof3]

Quote: Originally Posted by TrYiN2LaYaDiMe

. just take a break man sit back and think ull figure it out man ur just getting mad and working mad wont fix it trust me i know lol.

This is one of the first things I learned when I started school to become a Tech., walk away, eat a candy bar and come back.

[MadMikeZ28]

I am assuming those rods are the ones from an aluminum inspection cover too the motor. Just extra braces.
And that "Manual Valve Position switch" is the pressure switch.
Look in the link of the part I posted. That picture is of the top side of that switch. Its just named wrong in that photo.

[skunk0526]

This brace is connected to the side between the tranny & the cat (right side). There does not appear to be one on the other side. It looks like the rest of the weight is on that cross member. those are loose.



Any suggestions mike? or are you done listening to my pansy ass. He's probably sayin "JUST ****IN DO IT ALREADY!" LOL!

[jtcfanof3]

LOL, Mike is a great listener, pansy ass or not he will help, but in some instances he refuses to help some, but for good reason!

[MadMikeZ28]

Quote: Originally Posted by jtcfanof3

LOL, Mike is a great listener, pansy ass or not he will help, but in some instances he refuses to help some, but for good reason!

At least I think my reasons are good.

If the other end of that brace is hooked too the cat then it must just be a suport hanger.You should be able to jack the tranny up enough to get the pan out. You should not have to lift it lots. The minor things like tranny cololer lines will give enough and so will the exhaust hangers. If you feel its easy enough for you to drop the exhaust pipe up front then go for it. Might also be a good time to replace your exhaust bearings in there as well.

[skunk0526]

Unfortunately, this brace is not connected to to the cat. It runs up front into the abyss & cant see where its connected. Im goning to put a jack underneath the tranny & loosten it just to give it a bit more give.

Upon further inspection, the exhaust flange nuts & bolts look kinda weak, so i'm not going that route.

I WILL make progress tonight! Hell or high water! I think i can......I think i can!

Thanks MAD Mike!

[skunk0526]

ok guys. jacked up the tranny. still didn't clear the exhaust to drop it toward the front. used a pry bar to gently wedge the edge of the pan past the exhaust & succeeded but it wouldn't slide out because the accumulator is below seal level, so i cant just pull it out. The pan wedges between the cross-brace & the tranny and wont slide out because the accumulator protrudes down.
The gasket is shredded & all i'm thinking is "If i do get this apart, how am i going to get it back together & not ruin a new gasket". I'm worried enough about everything i've tried to just get the pan out, damaging something on the valve body, breaking something jacking the tranny....... seals.......etc.



Finally wedged the edge past the exhaust after this shot...........

only to be met by the pan not fitting through the crossmember & the accumulator on the valve body.......


I can probably get the pressure switch cover off with just the front dropped, but i wanted to do a full clean.... you know..... do it right. Bang up job so far

[TrYiN2LaYaDiMe]

good luck man that sucks ass mine was so easy and i hate saying that but i also have more room underneath my truck being a full size

[MadMikeZ28]

Bolt your pan back up and use a pry bar or something and bend those ears a bit. I think it has to come out from the back first. Its bassically the same as in my mom's truck (though I believe the 4x4 cross member is different but I had to move mine forward some) and her truck has an Edelbrock TES which has a bigger pipe.
And the gasket tore maybe because it was stuck to the pan and trans at the same time.
After all this I hope the switch fixes the problem!

[TrYiN2LaYaDiMe]

Quote: Originally Posted by MadMikeZ28

After all this I hope the switch fixes the problem!

[skunk0526]

even with the ears bent, the pan wont slide any further forward due to the tranny body being rounded out and wont allow it. Tried unbolting the exhaust but my wonderful socket set didn't come w/ a 14mm deep socket, so I'm getting one today and try this b.s again tonight. they are pretty rusted so im expecting the worst and hoping for the best.

Hope i didn't damage anything by jacking up the tranny that much. i heard a pop and a piece of plastic fell. hoping it was just a loom holder.

[MadMikeZ28]

The front of the pan will not go up over the pipe and foward enough to allow the back to drop past the cross member? I really don't know how I do it. I have a bit of trouble every time because I forget how I did it, but never this much trouble.

[skunk0526]

I've had advice from other sources & they are telling me to drop the brace. Im considering it cuz I've had it! I'm afraid I'm gonna damage the tranny if i keep jacking it up especially after i heard that pop. Besides the exhaust lifts with the tranny when i jack up the front. gives me no extra clearance. Borrowed a 24" breaker bar to git er done (hopefully i can break these bolts free). the side that sits over the frame is gonna be a BITCH! wish me luck!

[skunk0526]

Dropped the brace w/ only a 3/8 -15mm socket & down it came.

Finally a look at the elusive valve body.....


hmmmm, cross-brace. who would have thunk it?

[TrYiN2LaYaDiMe]

nice job man congrads on the win lol.