97 GA with recurring transmission and ABS codes

[19k40rocky]

I recently bought a 97 GA that has a 3.1 engine and a 3 speed overdrive transmission. Got two problems currently. First, it keeps throwing a P1870A code that is suppose to mean that a "Transmission component is slipping." I have noticed on the highway that sometimes it does seem to really shift into overdrive just from watching the tachometer. So am guessing it is on the 3-4 shift. I had changed the transmission fluid and filter about 2000 miles ago because it was looking like it had never been done. It was really dirty but did not smell burned. I had put MaxLife Mercon-Dextron back in it. What do you all recommend I do to solve/fix this? Can I take it to a dealer or transmission shop to have something adjusted or tightened up? Can I do this myself? Any information would be really helpful.
As for the other problem I keep getting 3 ABS codes C1293,C1296,C1298. They all are suppose to have something to do with the stoplight switch. I did get one of those and replaced it but still the same thing. Any ideas what to look for next?
Again any and all help is greatly appreciated!

[xeroinfinity]

Hard to say about the trans code with out further diagnostics, but you might get lucky and all it need is a band adjustment.

On the other codes ... I think you have a few more issues here.
C1293 - Code C1291 Set in Previous Ignition Cycle
-- C1291 - Open Brake Lamp Switch Contacts During Deceleration
C1296 - Brake Fluid Pressure Sensor Circuit

C1298 - PCM Class 2 Serial Data Link Malfunction

Is the brake presure switch what you replaced or the brake lamp switch ???
How are your tail lights working ?
Any water leaking into them ?

Does sound like you are having ABS troubles.
Have you tried using an ABS scan tool to cycle(purge) the ABS solenoids ??

[19k40rocky]

Thanks for the reply! I replaced the Brake light switch. It was the lower one of the two switches that were under the dash against the brake pedal arm. The tail lights work good and are dry. I'm not sure what you mean by purging the solinoids. I bought an OTC 4000 enhanced monitor off of ebay a few years ago since I was starting to own cars that were OBD 2. I used it to clear the codes and could hear something viberate or buzz up by the master cylinder for a couple seconds. Is that what you mean?
Also any ideas of things I can do to further diagnose the transmission problem? or just take it to the GM shop and let them make adjustments?

[xeroinfinity]

The noise is hard to say but your brake pressure switch is on/in the master cylinder, check the wires & plug.

Your best bet would be to take it to a trans shop and hav it diagnosed, probly cheaper then the stealership.

After you cleared the codes did they all come back ??

[19k40rocky]

When I cleared the engine codes it never comes back until we get out on the highway and drive a good thirty miles or so. Then it will pop on. The lights can come on about time in town or when slowing down off highway speeds. seems when using the brakes is when it pops on. I will work on getting it up to a shop to have them take a look at it. I will let you know what the find on that. Will also take a look at this pressure switch as well. Thanks again!