Suddenly yesterday my automatic transmission dosent want to shift up any more. The fluid level is good.reverse works fine. I could get it to shift @about 3000 rpm to second but thats it. Also the service engine light has been coming on daily for about 2 weeks and once in a while the sevice ASR light comes on as well. Any clues???? thanks in advance.

 

I would start by pulling the codes, the step by step procedure is in this link including the codes.

http://www.digitalcorvettes.com/foru...56&postcount=9

Since your 94 has the electronically controlled 4L60E transmission it is controlled by the PCM and you will notice transmission codes are listed.
You will need the Factory Service Manual to diagnose any codes correctly, but this should be a starting point, hope that helps.

 

Thanks for the help. I checked the codes about a week ago and got c 12 and h 36 and another. I think the h is for history. Anyway i will check again and am hoping for the best!!

 

OK,So got some codes.
1. C12
---
4.H36 H42 H22
---
9.H62
---
A.
---
1.0.
So 4 is PCM ?
AND 9 ABS/ASR?
What does it all mean??

 

H22 has to do with the throttle position sensor. I wonder if your system could be sensing WOT (wide open throttle) at all times. That would keep it from shifting normally.

 

Since your primary concern is the transmission not shifting with those codes my next step would be to troubleshoot the code 22 following the procedure in the 1994 service manual.
Assuming the link is correct for your 94, the code 22 indicates problems with the throttle position sensor circuit, which is a likely candidate for shifting problems, it is also an input to the ABS traction control.
Basic troubleshooting protocol when multiple codes are present is to diagnose the lowest numbered one first, then clear codes and road test to see if any others return, if any do reset, repeat the process as above.

 

I don't have a service manual. I will look at the Throttle position sensor. Not sure it will tell me anything

 

Hi
I had a similar thing happen ,, the car would not shift up ... there is a governor in the side of the trans that failed on my car ... can get to it without removing the trans ... take it to transmission specialist they wil be able to tel you what the problem is by driving it .

 

Good advice on A4's built prior to 1994, but since 4l60E transmissions have no governor it does not apply here.

 

I had a transmission shop tell me I needed an overhaul on my Malibu's Tranny, it turned out to be a bad throttle position sensor. I found this problem with a DVOM on OHM scale across the TPS, and noted a very noisy pot with a dead spot near WOT. Shop wanted $2400, TPS cost me $26.
Bottom line here is the Tranny's control circuit relies on good sensor data input in order to manage the trans properly.
Hopefully you have a similar problem.

 

So I bought a TPS (38.00 auto zone) put it on and now the idle is around 1300???
Not sure what to do next.

 

It means the TPS is putting out to high a voltage at idle. I'd bet the TPS is either the wrong one for your car or is faulty. (Earlier TPS bodies had oblong holes so you could pivot them on the mounting screws to adjust them. Starting in 1990, they did away with those unfortunately.)

Since your car was idling OK before you did the swap, put your old TPS back on but don't connect the plug. With a VOM, measure the resistance between terminals A & B on the TPS itself. It should be a relatively low resistance. Put the Auto-Zone TPS back on and do the same thing. If the resistance is more than 5% different, the TPS they sold you is either bad or the wrong one for your car.

There is something else: All the codes -- except the descriptor code C12 which is always there -- are showing as history codes which means that whatever the problem was that caused the codes is intermittent or was there during the last 100 engine starts but wasn't there when you pulled the codes.

Make sure the ignition is OFF, and leave the Auto-Zone TPS on for now (hook the cable back up to it.) Take your negative battery terminal loose for a few minutes to clear the codes out. Put the negative cable back on and do a test drive even though the idle is high. See if your tranny is shifting better.

Next, pull the codes again and see what you have regardless of whether the tranny is OK now.

No matter what happens, you need to get a TPS that will allow your car to idle where it's supposed to. But if the codes are gone and the shift seems OK, at least you'll know that the old TPS was the problem.

 

OK I'll do it. Thanks for the advice I will let you know what happens.

 

So checked the codes first thing and they were the same except for an additional on 9. which was H 64. Started the car and it was idling around 900. took it for a drive and it works fine!! I'll take it out later and see if everything is still OK

 

How much resistance difference was there between the A-Z TPS and the old one when you checked them?
Are you on the A-Z TPS or back on the old one?
You did make sure the TPS cable was plugged in tight before you went for the drive, right?
Do all the codes still have an "h" in front of them?

The PCM codes indicate you have a problem with low TPS voltage and you potentially have a problem with the opti-spark system.

Go back to the web site link above, print out the code reset procedure for the individual modules and perform them instead of pulling the battery cable loose.

Double check that they are all reset before you go for a drive and when you take the drive, stay close to home but drive long enough to get the car up to temperature.

Pull the codes again after driving the car and make sure they really are coming back.

If the codes come back, you need to check the TPS voltage. You car should be idling less than 900 RPM if the TPS voltage really is low unless you have an air leak around your throttle body butterfly, there is an air leak into the manifold elsewhere or the IAC is not operating correctly because there are carbon deposits in its bore and it can't ratchet closed enough.

The main thing is get the car up to temp, see if the transmission still shifts correctly once you do and pull the codes again when you get back to see if you still have some kind of intermittent situation that is causing the codes.

 

I have not checked resistance,not sure how to. I have the new TPS on and the idle came down to around 700. The car drove perfect this morning untill the service engine light came on. At that point it would not shift untill around 3000 RPM. I turned it off and restarted. Same thing. I turned it off and restarted again. same thing. I checked the codes again and got 1. C12 4. H36 H42 H22 9. H62 H64. restarted and it was back to normal,no problems.???? I will look at clearing the codes and see what I can do

 

Did you clear the codes and then check to make sure they were cleared before you drove it this morning? You've got the same codes as before and they are historical so clear them, check to see if they are really gone and, if the problem comes back, see if the same codes come back.

If they do, you're going to need help from someone with a scan tool that can monitor engine and transmission parameters in real time. They would need to put the ST in the capture mode and try to see what is happening. An intermittent is difficult to find and a capture mode scan tool is a good aid in troubleshooting because it looks at so many things all at the same time.

That said, doing a shake test on the wiring associated with the TPS is one other test to make since you're getting code 22. Start the car, get it warm and then shake the wiring to see if the idle changes.

If that doesn't cause any idle RPM changes, I'm afraid you're at the point where you need someone else take a look at the problem since you don't have a FSM nor the tools you need to troubleshoot the problem.

 

OK , So cleared the codes and started the car. It idled at 1500 RPM and the service engine light was on.Did the shake test on the wires and nothing changed. Checked codes again and got the H22 only. How do I check resistance at the TPS?? I have a digital meter just not sure what to do with it !!LOL. Anyway thanks for all the input!!

 

The resistance check was to be done between the two TPS sensors so that you could compare them and find out if Auto-Zone sold you a faulty TPS or the wrong one. The thing that is actually important to solve the problem is do you get code 22 on both of the TPS.

At this point, we need to find out if both of your sensors cause a 22 code. If they do, the 22 code is probably causing your tranny problem

You know you're getting the code with the TPS that is on it now so put the other TPS back on and clear the codes. Fire the car up for awhile, then shut it off and check the codes again to see if code 22 is there or not.

If it is, the easiest thing to do is to buy a TPS test harness from Corvette Central, Mid America, Ecklers etc. (From Ecklers, the TPS Test Harness for a '94 is P/N 26691 and it costs around $13.00.)

With the test harness, using your VOM you can determine that there is +5 volts coming to the TPS, if the ground is good and how much voltage is being fed to the PCM.

At this point, checking the resistance isn't going to do much for you except to determine if A-Z sold you something that is different than the stock TPS. Since you want to find out the source of code 22 at the moment, buy the TPS test harness (maybe A-Z also sells them) and determine the TPS voltage being fed to the PCM.

When you do, someone with a 94 FSM will have to tell you what TPS voltage you are supposed to have at idle and WOT. For my '90, the desired idle TPS voltage is .54 volts and WOT is just shy of a full 5 volts but a 94 may be different.

Get the test harness. It should have directions with it for measuring. When you have the voltages, report back.