Transmission Problems

Hello, I am new to this forum and glad I found it. I have a stock 97 Riv with 127k miles. I am having problems with my transmission which is in fail safe (limp home) mode. My problem actually began about a month ago when my car wouldn't start. It turned over, but would not start for about 30 minutes. Then, giving it a little gas it finally choked to a start. It has had this problem off and on since. Next, I was almost home, came to a stop and then the car lost 1st gear. It has been in fail safe mode off and on since. I've been limping it back and forth to work.
We just replaced the battery yesterday which had a bad cell and tested the alternator today and it is overcharging. I guess I am buying a new alternator tomorrow. I hope this solves my transmission problem. Any advice from anyone else who has had similar issues would be greatly appreciated.

Overcharging can cause odd transmission behavior. I had the same problem with 17v coming from the alternator. Transmission shifted erratically, seemed to slip at times. Back to normal after new alternator ANC battery.

AA wrote:

Overcharging can cause odd transmission behavior. I had the same problem with 17v coming from the alternator. Transmission shifted erratically, seemed to slip at times. Back to normal after new alternator ANC battery.

Thanks for the response. This has been a chain of events that has really concerned me this past week. I hope that my luck is as good as yours with the new alternator and battery.

I had the exact same problem. My alternator was pushing too much and put the tranny in limp mode. The problem is you're juicing the electrical system every time you run it. This has led to further problems with my coil packs and Ignition Control Module. I have replaced plugs, wires, coil packs and still having cut out issues even though the tranny is shifting fine after a new alternator. There is a thread on here " Idle Problems! " that goes through my nightmare which isn't over yet! Hope this helps and do keep us informed.

Thanks Samuel. We have replaced the neutral safety switch and now the battery. I'm getting the alternator today. Your scenerio is exactly what I am worried about. What else have I fried driving this car while trying to diagnose this problem? It gets me to work and then has been to the shop where my husband works every day last week for replacement parts, scans, to clear codes, etc. He is a mechanic (Thank God!) and my nephew is a transmission mechanic and this troubleshooting has been a trip for both of them. We are learning more and more about the complexity of the Riviera. I do love my Riviera, but not when she's running like this....every day. My fingers are crossed that the alternator "fixes" the problem.

I would ask Hubby to take some time as well and read through these threads. The Factory Service Manuals are cheap on e-bay and priceless in owning these cars

rivparadise wrote:

I would ask Hubby to take some time as well and read through these threads. The Factory Service Manuals are cheap on e-bay and priceless in owning these cars

"Hubby" might/should check the positive cable on the battery to see that it has the thermistor and that the thermistor indeed works.

We have the factory service manuals...I always buy them when I buy a used car. I read through this forum last night and freaked out a little over the chain of events with electrical problems. I am trying to keep the faith and pray that this alternator does the trick. I will ask my husband to check the thermistor. Thank you for lending your knowledge. I do appreciate the education.

My husband just came back with my car. I din't even know he had it. The new alternator is installed and he said he drove it out to the county line and back (about 10 miles) and it ran through the gears fine. Yay! The true test will be driving it to work tomorrow morning when the car is cold.
Thank You and Have a Very Merry Christmas!

Good news! Report back and let us know how things turn out.

Once you get the problems fixed it should be fine.

To get a jump on the maintenance please have a look at the threads concerning maintenance items, you might want to look through

https://rivperformance.editboard.com/t769-faq-high-mile-club-wear-repair-reports

if you have an hour or so on your hands.

my alternator is baddd too..and my trans has been acting funny as well..i am getting a 150 amp alternator this weekend..i hope this also solves my problem..because i do not want to have to rebuild or get new tranny..

Ok, the new alternator is in. The car ran fine after installation, but went straight to fail safe mode on the 20 mile ride home. I hated to even tell my husband. This has really been frustrating. This morning, the car was in fail safe mode again when I left the house. Power outages in town and no gas pumps sent me back home for 1/2 hour or so. When I started the car again it ran out fine all the way to work including a stop at the store for gas. It being so intermitent is what is so frustrating. I doubt I can get it back in the shop today. My husband's boss is tired of seeing my car in his shop. It's been there almost ever day this past week or two. We may be able to get a quick scan onit this evening, but I'm probably going to have to wait for the weekend...Christmas weekend no less. I asked my husband about checking the thermistor on the battery terminal. He just looked at me like he's the mechanic and why am I asking him these questions. I am just trying to help. QUESTION: This probably sounds stupid, but I'll use my gender excuse - we replaced a blower motor on the car a couple of weeks ago; Is it possible for that blower motor to cause any of this? When I start the car I hear it cycling - like the computer is checking the system or something. I never noticed that noise before, but usually have the radio turned up.
Good luck with your alternator Noah. I hope that fixes your tranny problem.

katrinasriviera wrote:

Ok, the new alternator is in. The car ran fine after installation, but went straight to fail safe mode on the 20 mile ride home. I hated to even tell my husband. This has really been frustrating. This morning, the car was in fail safe mode again when I left the house. Power outages in town and no gas pumps sent me back home for 1/2 hour or so. When I started the car again it ran out fine all the way to work including a stop at the store for gas. It being so intermitent is what is so frustrating. I doubt I can get it back in the shop today. My husband's boss is tired of seeing my car in his shop. It's been there almost ever day this past week or two. We may be able to get a quick scan onit this evening, but I'm probably going to have to wait for the weekend...Christmas weekend no less. I asked my husband about checking the thermistor on the battery terminal. He just looked at me like he's the mechanic and why am I asking him these questions. I am just trying to help. QUESTION: This probably sounds stupid, but I'll use my gender excuse - we replaced a blower motor on the car a couple of weeks ago; Is it possible for that blower motor to cause any of this? When I start the car I hear it cycling - like the computer is checking the system or something. I never noticed that noise before, but usually have the radio turned up.
Good luck with your alternator Noah. I hope that fixes your tranny problem.

If for some reason the positive battery cable has gone bad, it will cause problems with the battery and alternator. It's not a common setup, which is why DH looked at you like what are you asking -- he probably does not know.

The quickest way to diagnose this is with the *factory* Tech II scan tool. It will read the states of the sensors and such in the transmission in real time, making it quicker to figure out what is going on. If there is an electrical issue it will also be quicker to rule out a mechanical problem such as overheating transmission due to a clogged filter that forces the transmission into limp mode, or what have you.

Is my guess correct that DH's shop does *not* have a factory Tech II scan tool that reads the transmission codes? (many good independent shops do not, they are not frequently needed).

I think it would take me 2-3 hours to diagnose this with a factory scan tool. First thing I'd do is the "Electrical/Garage Shift Procedure" to check the signals. In my factory manual they are listed on page 7-103, there's like a dozen of them. This is where I'd start troubleshooting. In general assuming the transmission is mechanically OK an approach to electrical troubleshooting is needed to fix this and that's where to start.

The reason for asking about the battery cable - it's an expensive little cuss and difficult to get replacement if needed. and the car will run with an ordinary cable but won't charge properly in some conditions, which might be causing the problem. In the '98 service manual set see page 8A-201-37 for a pictorial showing the proper cable with thermistor. Point is that if the car was in a collision before you got it the cable may have been replaced with ordinary one. Other issue is the thermistor may have failed (most do not fail for a very long time)

Bottom line is the car seems to run normal for a while then falls into limp mode.

If the trans has ever been out or repaired I'd check the harness for damage and / or dirt.

You are correct that my husband's shop does not have the scanner you mentioned. However, my nephew has a transmission shop in the city and has scanned the car. The scanner indicated the problem with the battery. After checking the battery it was determined that the alternator was overcharging. Those items have been replaced. My nephew said it probably is electrical rather than the transmission. You certainly make a valid point about electrical troubleshooting. I have printed out your comments for my husband. We do have the manual so I'm sure we can locate the codes you mentioned.
I just returned from lunch and although the car started in limp mode, once I turned it off and restarted, it ran out fine the rest of the hour while I drove aimlessly around town just running it through the gears. It sure is a fine ride when it wants to be.
Thank you for your information.

Quote :

I asked my husband about checking the thermistor on the battery terminal. He just looked at me like he's the mechanic and why am I asking him these questions.

One way to rule out the thermistor is to simply measure voltage with the new alternator and battery in place. If the voltage is normal (13-15v running), you shouldn't be concerned with the thermistor. Maybe this was the reason for your husband's reaction.

Many, many things could cause the limp mode that affects the transmission operation, from misfires, to transmission behavior, to some other seemingly unrelated issue. Keep a record of all DTC codes when scanned. They are clues that could point to the problem. Also keep track of how long you drive before the limp mode begins, and what you & the car are doing at the exact moment it activates.

As for the blower motor, I doubt it's related. One way you might check is to run the car with HVAC shut off. See if you can activate the limp home condition without the blower motor engaged. I'm guessing your problem will come back, but if it doesn't for some reason, you know where your problem is coming from.

We know your frustration all too well. You'll get past it. Best of luck!

thanks katrina...and hopefully your problem is solved as well

What does a transmission do when it is in limp mode?

dtrumbo wrote:

What does a transmission do when it is in limp mode?

2nd or 3rd gear only (I forget which) and reverse.

Transmission feels like it's blown but isn't. Limp mode is usually an indicator there is still too much voltage. I had too much voltage running through my system and new alternator took it out of limp mode. Lots of parts later I think my Camshaft Position Sensor got fried. Changed it today and running better with no problems. Pay close attention after you get it out of limp mode. Although it's in limp mode to protect itself, not everything electrical is protected.

Mine shifts into all gears in limp mode, but PCM maxes trans pressure to 96. This results in very hard shifts. If fluid temp is hot, and TCC is not locking up, the trans may shift into 3rd for better cooling. Usually a 10-20 min shut down will reset the mode to normal - until a problem is encountered again.

--------------------------------------------------------------------------------

Hey, I just wanted to let y'all know what we finally found out about my car. It was in limp home mode (2nd and 3rd gear only) what seems like forever and we went through the various scenerios. We replaced Neutral Safety switch, then the battery and the alternator was overcharging so we replaced it and then the new alternator was overcharging and Mr. Aficionado mentioned the thermistor which is located between the battery and the fuse. So, we checked the thermistor and that was the problem. We actually have it disconnected from the battery at the moment until the new one comes in. We were told by Buick that we could do that and it would just make the battery light come on which it did when we disconnected it. However, the car has been running fine ever since and it's been over a week now. Yay! Thanks to all who helped us through this nightmare! I also hope these posts will help others with similar problems. I wonder how many people have replaced their transmissions thinking that was the problem.
Thanks again and Happy New Year! Katrina

albertj wrote:

rivparadise wrote:

I would ask Hubby to take some time as well and read through these threads. The Factory Service Manuals are cheap on e-bay and priceless in owning these cars

"Hubby" might/should check the positive cable on the battery to see that it has the thermistor and that the thermistor indeed works.

Bingo.

Albertj

katrinasriviera wrote:

I also hope these posts will help others with similar problems.

absolutely it did for me!!

OK this is why I´m thinking this is hapening to me: my tranny started on this "limp mode" (2nd and 3rd only) this morning and I just freaked out because it´s the only thing that keeps me moving, so I immediately checked the fluid level because I know I have leak at the oil pan and both cooler lines, so indeed it was very low and I bought a qt. of tranny fluid and poured in about 1/2 qt. In it, so I started the car again and it worked fine and I thought that it was because of the low fluid condition that it was not engaging on the 1st & 4th gear. And no TCC lock up. Then after coming out of work the car run fine for 2 min and then again no 1st gear, etc. So I condemed the tranny. ;( then after reading this post that describes my problem it all makes sense now because last week when I fixed my car I overtighted the neg batt terminal as I was using an 'adapter' from post to side terminals, so for a week I was driving with a loose neg terminal cable to the point that I had to lift up the backseat and like tight the terminal to the battery to start the car, and well the vibrations sometimes made the cable loose and I was able to see voltage spikes as the lights started to dim to the point that will shut the engine down. So I guess after that the alternator got damaged when I finnaly was able to buy a new Batt terminal adapter.

Tomorrow I'll check the charging voltage and diagnose the alternator, but I do have a question: where exactly is the thermistor at? And how do I check it?

P.S. Man is hard to write with ur ph with one hand´took me 'bout 20 min.

Ok, well today I checked the alternator charge and I think it was a little high up to 15.60V - 15.70V and looks like the battery keeps a charge of 12.70V that I think is high for me also. Although the car has been running fine this worries me a little.