cat efficiency failure code please help?????

[truck150]

i have a 02 grand prix se withthe 3100. the engine light comes on and when i had it check it came up as cat converter efficiency failure. so i put new new o2 sensors and a new cat. a week later it was back on. i had it erased anda week later came back on same code. it has been like this for about 3 months. meanwhile i went from 30 mph to 23 and it stays at 23. cant figure out what is going on. also i had the egr replaced. anyone know what is going on.

[BNaylor]

What replacement parts did you use. Were they aftermarket or OEM GM/AC Delco. Were both 02 sensors replaced....before the CAT and after CAT?

Also post the odb-ii DTC error code such as P0420.

[truck150]

02's were oem and i replaced both of them. the cat was an after market cat but still obd II compliant. and no i dont have the code i never recieved it. the guy said that it was a cat failure but i changed all of the things that work with the cat so i am stuck now.

[BNaylor]

Originally Posted by truck150

02's were oem and i replaced both of them. the cat was an after market cat but still obd II compliant. and no i dont have the code i never recieved it. the guy said that it was a cat failure but i changed all of the things that work with the cat so i am stuck now.

Normally when you get a CAT convertor efficiency DTC error code it will trigger the SES light so if you can re-scan and post codes someone should be able to help you. The codes will help pinpoint the problem or get you in the right circuit. Although the sensors have been replaced it doesn't rule out the wiring and voltages both reference from the PCM and 02 sensor heater.

I have an aftermarket odb-ii compliant hi-flow CAT and never get a CAT efficiency error code but you never know about aftermarket CATs.

[truck150]

ok i will see if he can get the code for me tomorrow and i will post it when i get it so keep your eyes open for a new post. oh and thanks for your help i appreciate it