1991 SSE - code 28 code 39 code 42 - losing sleep
 

I am wondering if anyone out there can lend a hand with some problems I am having with my 1991 SSE.

A couple weeks ago, on my way out to Colorado from Chicago, my SES engine light came on and I started to have some problems with my car. Basically, the car seemed to lose power while I was driving. I would press on the accelerator and the rpm's would not rise. I couldn't really go more than 50 miles per hour on a very mild positive grade. If I floored the gas, the rpms would rise a little, then SLAM into the lower gear and rise to 4500 or 5000.

I limped it off the side of the road and checked codes. I got code 28, code 39, and code 42. I checked a few hoses. Two looked a little old. I went to the auto parts store and replaced them. I checked the spark plugs and wires and all seemed fine and properly gapped. So I got back on the road. It seemed alright for a while and got me to Denver.

Recently, I took it into the mountains to ski. On the way up it began to stutter for a second, then the SES light came on, then I lost most power in D and the car didn't want to go over 2000 rpms. Then it would SLAM into second for a while, then back into third, then SLAM into second again. I just ended up keeping it in second and driving at 4000 rpms and 40-45mph up a 6% grade.

Now it is not just the mountains that make it shift hard into a lower gear. On flat land, when I quickly floor it while moving at 25mph, the car revs slowly in D, then SLAMS into second at 4500-5000 rmps.

Side note, if I am driving the car around on relatively flat highway and the SES light has not been triggered, then I can make it to 75-80 miles an hour. Once it gets triggered, I am robbed of power and need to pull it over, shut it off and restart it again. Usually the SES light won't come back on right away when the car is turned off, then on again.

I love this car and keep the interior and body in perfect shape. I don't mind putting time and work into it. Unfortunately my Haynes manual is not helping diagnose the problems at the moment and my personal automotive experience is not with engines or transmissions yet.

Have any of you seen this problem before or had experience with triggering these specific errors?

Thanks

This is what those codes mean and some places to start looking at to correct:

Code 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.

Code 39

Torque Converter Clutch Check ECM connections, check for faulty Torque Converter Clutch solenoid.

Code 42

The Electronic Spark Timing (EST) signal did not change when the ECM applied bypass voltage to the ignition module. Check for faulty connections, or a faulty ignition module.

Sounds like when the SES light goes on the car is in limp home mode. Does this to protect it's self. The problem seems to be transmission related. Start by checking any vacuum hoses that go to the transmission. Also check all wires and plugs to the transmission. A intermittent problem suggests to me a short or vacuum leak.

During my wiring check I found the wires going from the top sensor on the EGR valve had been damaged by heat where they were close to the engine at the bottom of the old leaking EGR valve (recently replaced). The wires were exposed, melted and fused together. I imagine this could be a major part of my problem. I cut out the fused part and am splicing the wires back together and wrapping them with heat resistant tape. Also, I had to remove the ground from the other group of wires that connects into this fuel injector harness into the driver's side of the engine. When I removed it, it broke. I need to crimp a new connector on it. However, I am not sure if it was already deteriorating when I went to remove it, so maybe i had a bad ground too. Do you think this is the problem causing code 42?

What could cause the triggering of the 3rd gear switch malfunction, code 28? The hoses and vacuum lines seem to be in good shape. Although, there is a 2 inch round galvanized cylinder on the front of the transmission that seems to be rusted pretty well. Is this the vacuum modulator? Is there a way for me to test that to see if it is bad?

I checked the five pin connetor that plugs into the front of the automatic transaxle. It looked clean. However, the plastice female connector fitted inside the trasmission housing was a bit loosely fitting. I can pull it back and forth about an 1/8th of an inch. Is this normal?

I am going to perform the test for the TCC as soon as I review some other posts and learn how to do it.

Thanks the help. Hopefully one day I will be a Certified Bonneville Nut. Is there any specific Bonneville year that is known to be the best of all of them?

Tha galvanized cylinder on the front of the trans is the vacuum modulator. Remove the vacuum hose from it and rotate it so the nipple is @ 6:00. If fluid come out of it, it's bad. If it is rusty, you may want to replace it anyway.

Code 28 could be cause by 3 basic things: 1- bad switch; 2-bad wiring; 3-bad computer. I believe that the 3rd gear switch is normally open, so when the trans shifts to 3rd, it closes and goes to ground to let the computer know that it in 3rd gear. You should easily be able to check it's resistance with the trans in the car.

Don't worry too much if the main case connector is loose as long as it is still in place and not leaking.

Correct your wiring problem and let us know if your problems are corrected.

I fixed the wiring. Code 42 is no more. Additionally, I have not triggered code 39 the Torque Converter Clutch, since the wiring has been redone.

Code 28 is still bothering me though. I have checked all of the hoses going and going from the transmission. I also seem to have a general lack of power. Also, when the accelerator is pushed down to the floor, the car downshits with a heavy, car jerking shift.

Could my engine control module be bad and this be causing transmission problems?

You will need to find the wire at the transmission case connector that goes to the 3rd gear switch and do a resistance test to see what happens.

Cool, according to the factory service manual third clutch switch is position C on the Wiring connector to the ECM. It appears that it should test 12V. Does that seem right to you? I will test it tomorrow.

I just bought a new vacuum modulator. The orginal is 20 years old and for 20 bucks I figured it wouldn't hurt. That will be on tomorrow too.

Does any think it could help to put a new ECU and Ignition module in it? Does $100 bucks for the ECU and $60 for the Ignition module seem right?

Thank you

Don't throw parts at it!

The 3rd clutch switch wire should have 12 volts until the cars shifts into 3rd and then it should go to ground.

Diisconnect the case connector and place the positve lead of an ohm meter on pin C and put the other lead to ground and see what the resistance is. If you get no reading, you have an open wire or switch.

If you have access to a scan tool, you will be able to view the data to see what the switch is doing.

I mis read your post! I thought that you meant pin C @ the trans case connector!
Unplug the ECM connector and do the switch resistance test from there.