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DTC 68 - Transmission Component Slipping

kimagine

kimagine

A(ACLU) Agent xXx Skeeter
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Location
Cincinnati, OHIO
Evening everybody.
My 4l80e was just recently rebuilt and it finally came back to my possession incomplete(long story) and is having some shifting issues and the scanner they were using would not read info from the TCM to the trans but when tested bypassing the TPS, the trans shifted fine. Any thoughts on what it may be? I will be checking all grounds this weekend and will try to chase all related wiring to see if something is amiss.
I would appreciate any info that someone may have that may have been through this issue in the past.

Thanks,
Mark
 
Replace and adjust the TPS. All it is for is the trans anyway.
 
Know anybody with an old snap-on brick scanner, they'll work.

Drive around in drive(not overdrive), find a hill, apply some throttle but not enough to unlock the converter. See if you get a DTC 39. Thats what mine started doing after awhile with the DTC 68, it had a bad converter clutch.

Sent you a PM.
 
WarWagon said:
Replace and adjust the TPS. All it is for is the trans anyway.
Click to expand...

That has been done and adjusted by the GMC stealer. Just about everything in the trans is new including triple disc converter and all sylonoids.

The job was over $4200.00 but since it was not corrected, I got the truck back after only paying around $2500.00.
It may need to be rechecked by a place that knows more about it.
I'm told the tranny itself works perfect when bypassed and run from the testing maching, it will just not comunicate with the new TCM(also installed by the stealer).

Thanks,
Mark
 
midniteplowboyy said:
Know anybody with an old snap-on brick scanner, they'll work.

Drive around in drive(not overdrive), find a hill, apply some throttle but not enough to unlock the converter. See if you get a DTC 39. Thats what mine started doing after awhile with the DTC 68, it had a bad converter clutch.

Sent you a PM.
Click to expand...

Got it and checked it out and thanks. No idea on the scanner but will have to check around. I don't have a whole lot of $$$$ to play with right now. Being without this truck has caused me to lose out on some bigger jobs that my back up Ranger just could not handle. Breaking my hand did not help work matters either. lol

Thanks,
Mark
 
Jess_sr said:
Code 68 in a 93 is a OD error.
Click to expand...

Thank you and I'll see if I can get someone over this weekend to help with checking all the circuts, grounds power sources.

I did have a battery with a bad cell and it killed them both and I replaced them the day I had to pick the truck up.

Thanks,
Mark
 
Did they update the pressure control solenoid to the new style(94 and later)? If they did, did they mod the separator plate(plug a hole) and valvebody(drill a hole) for it.

Sounds like the new TCM is bad, if it wont communicate. Did the old TCM communicate. Might try a 95 van, VIN "Y", IIRC as the vehicle. Was the new TCM used as an update for the new style pressure control solenoid, this might be the communication problem, try a later year mechanical IP 6.5 instead of a 93 vin "F".
 
midniteplowboyy said:
Did they update the pressure control solenoid to the new style(94 and later)? If they did, did they mod the separator plate(plug a hole) and valvebody(drill a hole) for it.

Sounds like the new TCM is bad, if it wont communicate. Did the old TCM communicate. Might try a 95 van, VIN "Y", IIRC as the vehicle. Was the new TCM used as an update for the new style pressure control solenoid, this might be the communication problem, try a later year mechanical IP 6.5 instead of a 93 vin "F".
Click to expand...

Supposedly the TCM went bad and killed the TPS which in turn burnt up the tranny which was why all had been replaced. The new TCM should be under warranty from the stealer and I'll have to check the paperwork on the pressure control solenoid.
Supposedly a very reputible trans shop and I've seen no complaints.

Thanks,
Mark
 
I went to the truck and grabbed the receipt. Here is the list of replaced parts:

TPS
PCM
(dealer items)

Tranny and cooler flush with cooler clean
Master overhaul kit, high energy
Torque converter, billet cover, multi-disc lockup
Tranny oil
Internal filter
Pressure control solenoid
Shift solenoid
Seperator plate
Lock up solenoid
Intermediate drum
Internal band
Pump gears
3-2 downshift solenoid
dismantle, inspect and clean transmission, paint case, rebuild transmission assembly and rebuild valve body assembly.

Not sure of the pressure control solenoid and plate but I would assume when it was ordered together, it should be correct. You never know though.
I would have though this should have covered all aspects of the issues but here I sit.
I am wondering if it an electrical gremlin in there and will check the list posted above as well as anything else I can handle on my own(kinda). The other ideas I will have to forward on to another shop.

Thanks,
Mark
 
for what it is worth to ye.

i dealt with the same prob,changed all solenoids, checked all related electrical components ie wiring, connectors,TPS,TCM,with no change,decided to overhaul the tranny myself,I basicly found notting wrong in it.
And of story is,i had a intermittend VSS.
In your rebuild list there aint VS sensors mentioned, mebby should look at them.
 
Wow. I just had my trans rebuilt as well for OD blowing up. Drum, gears, Sprag, and bearing. It first had code 68 and after the 'bang' code 8x ratio errors. I paid for all new electronics in the trans just to be sure.

DTC 68 is known as transmission component slippage in the Hayes book I have. Was any repair or checking done on the TCC valve as they tend to wear out and need to be sleeved.

Are you getting codes via a paperclip? If the TCM will not communicate with the scanner and will not flash codes it has a grounding or supply voltage problem. (ign switch?) The voltages have to be right for the computer to enter the diagnostic mode. Had an S-10 that would not go into this mode. Several nasty ground wire splices were fixed...

Just because the rebuilt 'new' computer is "new" doesn't mean it is working 100%. If the dealer Tech II or whatever can't communicate with it it has the voltage issues or is simply bad. Perhaps even bad wires to the ALDL. Why they sent you down the road like that? Need another larger dealer?
 
WarWagon said:
Wow. I just had my trans rebuilt as well for OD blowing up. Drum, gears, Sprag, and bearing. It first had code 68 and after the 'bang' code 8x ratio errors. I paid for all new electronics in the trans just to be sure.

DTC 68 is known as transmission component slippage in the Hayes book I have. Was any repair or checking done on the TCC valve as they tend to wear out and need to be sleeved.

Are you getting codes via a paperclip? If the TCM will not communicate with the scanner and will not flash codes it has a grounding or supply voltage problem. (ign switch?) The voltages have to be right for the computer to enter the diagnostic mode. Had an S-10 that would not go into this mode. Several nasty ground wire splices were fixed...

Just because the rebuilt 'new' computer is "new" doesn't mean it is working 100%. If the dealer Tech II or whatever can't communicate with it it has the voltage issues or is simply bad. Perhaps even bad wires to the ALDL. Why they sent you down the road like that? Need another larger dealer?
Click to expand...

I will have to check on the TCC thing but, could a cut wire and not being spliced together properly at the TPS harness give me this problem? Kinda like this one....(This was just a quick look when I came home from work tonight and it was dark out, but it looked starnge and was not there when I changed the TPS out a few years back). Crap, it won't let me load the pic! (or the smiley Mad2.
 
Heres the pic of what could be wrong. Maybe GMC dealer or the Tranny shop.I know the green shrinkwrap was not there when I changed the TPS a couple of years ago.Thanks,Mark
P.S. Thanks for assistance Paul! :)

attachment.php
 

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  • TPS splice.jpg
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BTW, do any of you tranny/electrical experts know what the blue wire in the center of that harness is exactly for? The lower end pulled out very easily which tells me there was not alot of contact. A little more research this afternoon, I found on the back of the new TCM wiring, another splice(another blue wire) but have not messed with it yet due to darkness and family obligations.Thanks,Mark
 
The black wire is the sensor ground, the gray wire is the 5 volt reference, and the blue wire is the TP signal that tells the TCM the throttle angle. Voltage on the blue wire should be low (.5v) with throttle closed and high (4.5v) at WOT.
 
Thanks guys, I would love to multi quote right now to answer and ask correctly but I seem to have a registry error not allowing me to quote, smiley and other things.Any thoughts on the wires coming from the TCM? There are a few blue wires on the back end of the harness but the particular one I'm speaking of is on the right hand side of the box in the left side of the right most plug in. Could they be connected to the same wire somehow?I don't have the proper tools or scanning equipment to find out. I'm just going by sight and looking at what might be obvious.Thanks,Mark
 
Did you get it figured out?

Is that 12pins wide or 16pins wide plug your asking about? There are letters(for which row of which plug) and numbers(what position in the row) on those plugs, like A12 or D16 stamped on the plugs.

I think your talking about C1 or D1(16 pin wide plug, 32pins total).

C1= ground Black/White

D1= I dont think its used



TPS related wires,

"A TPS" (5v reference) = C4 Gray(and D14, maybe)
"B TPS" (signal) = D8 Dark Blue
"C TPS" (ground) = C3 Black and D7 Black

I wouldn't trust the wire colors, GM did many things. Pin letter/numbers are correct though.
 
midniteplowboyy said:
Did you get it figured out?

Is that 12pins wide or 16pins wide plug your asking about? There are letters(for which row of which plug) and numbers(what position in the row) on those plugs, like A12 or D16 stamped on the plugs.

I think your talking about C1 or D1(16 pin wide plug, 32pins total).

C1= ground Black/White

D1= I dont think its used



TPS related wires,

"A TPS" (5v reference) = C4 Gray(and D14, maybe)
"B TPS" (signal) = D8 Dark Blue
"C TPS" (ground) = C3 Black and D7 Black

I wouldn't trust the wire colors, GM did many things. Pin letter/numbers are correct though.
Click to expand...

Not yet as I've been working past dark and it's been cold and wet here not to mention the wind storm today. I will try to get out there this weekend and I will look at the back of the tcm and get you the exact wire/pin it comes off of. I will also pull the fuse for the ecm/tcm and clear my codes and then re-run them to see if they clear and then drive the truck to see if it reappears.Thanks,Mark
 
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