PontiacBonnevilleClub.com

I'm driving along all morning very slowly due the subdivisions I'm in. Get on the Interstate and
only do about 60-65 for 20 miles or so. Back to slow driving around town, and suddenly the service engine light comes on, and the next thing I know it dosen't want to upshift unless I let off the gas. Does this a few times and I head home. Now I'm pulling into the driveway and it dosen't want to downshift, but does so with a thud.
What the _ _ _ _ ? I changed the fluid and filter back in February after putting in some Sea Foam for about 500 miles, and nothing looked bad.
It's got about 75,000 miles on the trans. By the way, it's about 93 degrees outside and the humidity is about the same. Anybody have any ideas?

I think the key to everything lies with the check engine light. You will want to get the codes scanned. You can usually go to a place like Autozone, OReilly, etc and many will scan the codes for free.

Randall,

I just got back from Advance Auto. They scanned a Throttle Position Sensor issue. According to the tech there, this can wear overtime in certain positions where a majority of the driving is done, ie. 35-45 mph. This will cause issues where the computer is not sure what your doing and not signaling the the engine/trans what to do. Therefore it can cause the shifting problems I had. A new sensor is only $35.00, so I might install one if this continues. But nothing unusal happened on my way there or back? So I'll wait and see.

It could be an intermittent failure, or it could also be a wiring or connection issue as well. You may find this tech info article to be of interest:

http://www.pontiacbonnevilleclub.com/fo ... =48&t=9098

The TPS tells the the Transmission tables where the engine is at, so it is most likely your problem. Replace it and see what happens.

Thanks for the info.
Took the TPS off, checked and cleaned all connections and reinstalled. Went for a ride and
all seems well, including the SEL went out!

Take a volt meter and check if you have a dead spot in the TPS. Key on engine off, full throttle should be close to 5v and off throttle should be 0 or about a half a volt.

And id be careful calling people at advance "techs"

EDIT:
should tell you what to look for with the volt meter. Start with throttle closed, and slowly open it while watching the meter. Volts should get more with the farther you open the throttle. If you notice that the meter drops out while you are opening the throttle, your TPS is bad and replace.

I'll check it out. If it's bad, I'm only out $35.00 for a new one.
By the way, I get your point about calling the Advance Auto guy a tech, but I have to say he knew more than all the parts counter guys I have ever encountered.
Most give me a look that says, "I have no idea what to say, or what you want, so I'll make-up something", when I ask a question.

It's been several days now, and the problem of shifting is intermittant. It only occurs after I have been driving for quite awhile. The SEL light will come on and the trans will not upshift properly, and will sometimes not downshift properly. After letting the car sit and cool awhile, all seems ok. The SEL light will also go out sometimes. I replaced the TPS, but it did not solve the problem even though the code indicates it as the problem. I'm assuming that as the trans
heats up, the problem surfaces, and then goes away after it cools down? I changed the fluid
and filter last February so that should not be an issue.

Sounds like shift problem is PCS.

Does it whine at all when it gets hot?

No, I don't hear anything unusual. After driving for about 20 minutes today, the SEL went out, and all appears well. But the outside temp is much lower today than it has been for the past few weeks.

what type of tps sensor you get?

It's a BWD product, made in USA.