I have recently started doing my own car repairs whenever I can so I should be considered a novice :) I have a 94 oldsmobile cutlass cierra. A few weeks ago it developed an interesting problem that seems to be related to the transmission. I will give as much detail as I can. When the car is cold it seems to run fine. But when it heats up it shifts late from first to second then when it is in second it seems to be shifting back and forth from first to second as I go down the road. After a short amount of time the "service engine soon" light will come on it stops doing that. So after the engine light is on I can drive the car normally without any shifting problems. One more detail that I should mention. About 4 days ago this stopped. And the car ran fine until this evening. So for 4 days this problem stopped. Then recurred this evening. Anyone have any ideas on what this could be? Is there a module of some type that controls the transmission? Any help will be greatly appreciated.

Is anyone out there?

You need to have it scanned with a trans capable scanner for trans codes, step one.

You need to have it scanned with a trans capable scanner for trans codes, step one.


Thank you for the reply. I did that. It came back with a "speed sensor" error. Apparently a sensor which detects the speed and indicates when the transmission is to be shifted (all this is info from the mechanic). I had this changed and it does the same thing still. Again not all the time. Only occasionally. Thanks for any input.

Another clue is that when the car is exhibiting the shifting problem the speedometer does not work. Again any ideas would be appreciated as I seem to have stumped the two shops I have taken it to.

you have a problem with the wiring going to the computer from the speed sensor u just replaced. it's broken somewhere. when you have no speedo the car goes into 'default" mode which boosts your line pressure and its is causing your problem. good luck

you have a problem with the wiring going to the computer from the speed sensor u just replaced. it's broken somewhere. when you have no speedo the car goes into 'default" mode which boosts your line pressure and its is causing your problem. good luck

Thanks for the info so far. Now my next question is where is this sensor at and where is the computer located so I can trace the wire. Thanks again..........

Thanks for the info so far. Now my next question is where is this sensor at and where is the computer located so I can trace the wire. Thanks again..........


Is there an online reference for this type of information?