Make:   Pontiac
Model:  Sunfire
Year:   2001
Engine: 2.2 L
Trans:  Automatic 

Hello to every one, bought my first car and it is fine except for this little annoying problem. After driving it for a while the trac off light goes on and the RPMs start to go really high 3K ~ 4K, the transmission does not upshift gears and when it does it kicks a bit hard and I've noticed that if I let go the accelerator the car sometimes shuts down, this problem comes and goes, it goes away if I stop using the car for a while but eventually comes back, I had the car scanned at autozone and at a transmission repair shop they obtained the following codes:

P0122 - Throttle Position Sensor
P0420 - Catalyst System Efficiency Below Threshold
P0742 - Torque Converter Clutch

I have a few questions regarding the codes:

  • How serious are these codes?
  • How reliable is the diagnosis of the scan?
  • Which of these are DIY'able?
  • What's the recomended order to fix them?

Thank you for all your time.

1 Answer 1


I just want to let everyone know that I replaced the TPS and the tracc off problem disapared, I'm only left with the catalyst code.

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