P0428?

[lance1010]

Hello everyone!

My car has been running very poorly lately. I have a 2000 GT 3.8
I have some trouble codes-
P0128
P0428
P0440

I have looked these up and can't seem to figure out what P0428 is for.

Anyone know?

[goser]

P0428 - Catalyst Temperature Sensor High Input (Bank 1)

(From http://www.automotiveforums.com/vbul...d.php?t=553044)

[BNaylor]

Originally Posted by lance1010

can't seem to figure out what P0428 is for.

Anyone know?

P0428 is a generic DTC that is probably not applicable to your year Grand Prix or any Grand Prix with a SII 3800 for that matter.

It sounds like a fluke or bogus DTC to me. To start the PCM is not programmed to generate that DTC and there is no catalyst temperature sensor, therefore it is not a valid fault. I do not see any diagnostics data about on it in either the GM Mode 6 listings or the GM service manual. What brand and model scanner was used?

Welcome to AF.

[lance1010]

Originally Posted by bnaylor

P0428 is a generic DTC that is probably not applicable to your year Grand Prix or any Grand Prix with a SII 3800 for that matter.

It sounds like a fluke or bogus DTC to me. To start the PCM is not programmed to generate that DTC and there is no catalyst temperature sensor, therefore it is not a valid fault. I do not see any diagnostics data about on it in either the GM Mode 6 listings or the GM service manual. What brand and model scanner was used?

Welcome to AF.

Thanks! I had a friend plug a scanner in. I don't know what kind it is, but it is orange in color. I'm just trying to figure out why the car is running so bad, accelleration is very poor. It looks like I might need a new thermostat, but would this make the car run the way it does.

[BNaylor]

Quite possibly. I would concentrate on the P0128 DTC. It will affect fuel injector trim levels and will prevent the PCM from switching odb-ii controls to the closed loop mode. Could be the thermostat or ECT sensor itself.

On the P0440 DTC it is a large leak normally a flaky gas cap seal. I never heard of it causing driveability problems but you never know.

[lance1010]

More codes came up on the scanner p0300 multiple cylider misfire. Ahhh.

Must be coils huh?

[BNaylor]

Originally Posted by lance1010

More codes came up on the scanner p0300 multiple cylider misfire. Ahhh.

Must be coils huh?

Not a good sign but better than the other DTCs explaining the performance loss. Random misfires could be the coil packs or even fuel injectors. More than one bad spark plug or ignition wires can cause it too. If you haven't replaced them in a while I'd start with spark plugs and wires. Also, replace the fuel filter if old.

[lance1010]

Bad news, I took it to a local mechanic and they said I need a new shrader valve, a new gas cap and a new Cat converter. $730

Any advice? Thanks.

[maxwedge]

Hold up on this, the cat is still under warranty for at least 7/70 and I believe it was extended to 120k, call you Pontiac dealer for the low down. Schraeder valve for what?

[richtazz]

Get an aftermarket hi-flow converter, way cheaper than the OEM, and better performance too. You can get a gas cap for under $10 at any auto parts store. $730 is highway robbery.

[BNaylor]

Big time rip.

BTW - The GM CAT initial warranty is 8 years or 80K miles, whichever comes first. Since he does not have a 2001 - 2002 model the CAT warranty extension to 10 years or 120K miles is not applicable. But it would not hurt to ask GM or the local GM dealer.

[wlkjr]

Originally Posted by richtazz

Get an aftermarket hi-flow converter, way cheaper than the OEM, and better performance too. You can get a gas cap for under $10 at any auto parts store. $730 is highway robbery.

Was Vaseline included and the customary kiss?

[lance1010]

Update!

Well I ended up getting another estimate somewhere else, this time at Midas. They quoted me in the $400 range. Turns out my 'shrader valve' was ok, Midas was like wtf? The first place said this was in my fuel line and it was leaking...... Total bill ended up being about $275 for the new catalytic converter. The car was becoming undrivable and I had this done just in time.

Thank you for all of the help! Its not easy troubleshooting over the internet.