2004 Pontiac Grand Prix - PCS Issue and.........?

I have a 2004 Pontiac Grand Prix with 140,000 miles on it. I have had an issue with the Pressure Controlled Solenoid for a few months and between not having the time to fix it myself to not wanting to pay for the timely and costly fix I’ve been able to work around it. That issue is when the car has been heated up, 15-20 minutes at least, it will sometimes shift awkwardly between 1st and 2nd gears. Shutting off the car seems to fix this and when the car is cold there is never an issue. From everything I have read repairing the PCS will fix this.

Yesterday my car started to feel like it was shifting hard between 2 and 3 and 3 and 4. When I say shifting hard it actually just feels awkward so I’m starting to think I just need to replace the PCS quickly. But even when I am up to speed, going past 60 mph on the freeway, the rpm’s are jumping around. It almost feels like the car is going to cut out at times. I played around with the speed driving into work but there was no real way of improving it. I checked my fluids and they are good.

I know the PCS needs to be replaced. Would the RPM’s jumping around past 60 mph’s be connected to this as well?


Cory, your PCS may or may not need to be replaced. But you can’t figure that out by web. And many of the people who’ve thought they needed a new PCS didn’t. And many of the shops that thought a car needed a new PCS were wrong. The PCS legend came from a now outdated TSB about shifting problems in these transmissions. But even then, note that the TSB came with a whole series of diagnostic procedures that went before PCS replacement.

Anyway…if the PCS was easy to replace I’'d say “why not.” It would be cheaper than paying for a diagnosis and might work. But it’s under the sidecover of the transmission and the whole driver’s side of the subframe has to be dropped to access the side cover. It’s not easy and IMO, not worth it on a guess.

What is the history of service on this transmission? Fluid? Filter?

  • You need to have the car scanned for error codes, and it needs to be done by someone with GM Tech II scanning capabilities. There can be lots of codes in there that hide from other scanning equipment. If you get some error codes you can post them - in specific form - e.g. “P0123.”
  • You should check out the engine bits most essential to transmission function - throttle position sensor, MAF & MAP sensors, coolant temp sensor, and speed sensor. The easiest way to check these things out is with a scantool, but if you have a repair manual many things can be checked with a digital multimeter.