3800 P0420 code....

[SnM]

I had that code once, but that was because of my R/T cat. flowing too much i guess, and the car thinks it is a bad converter.

well, denise's brother has a 98 lumina LTZ and he has that code. Is the only cause a bad converter, or is there something to look at with the autotap to see if the sensor is bad?

Thanks.

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[CoolGTX]

if his system is stock, id say its the sensors bad

 

[sr71_rgl]

420 means it's time to spark it up yo ; ) Seriously though I think it's a cat converter inefficiency code. I got it after the install of my rtdp.

 

[beyerch]

P0420 usually occurs when either the rear o2 goes back, or someting happens in the cat, or most likely when you replace the stock setup with an aftermarket one such as the RT DP.

They "swear" the RT pipe does not cause this problem, but trust me i've seen way too many of them set p0420's.

Does this mean that something is REALLY wrong with your emission system. MAYBE / MAYBE NOT. Basically the PCM is looking for a specific difference between the reading in the front o2 and the rear o2. Anything outside of a certain variance will set this light. Just by modifying the flow characterists could cause the second o2 sensor to report a value that triggers the po420 even though there may be no real difference in exhaust emissions.

If you know the system is working properly, then you should spoof the 2nd o2, put tape over the SES light , or pull the code from the pcm......

charles

 

[SnM]

this car with the code is stock, so is there something that i can look at with the atap to find out if it is the cat or the sensor?

Thanks

steve

 

[mybluegtp]

sorry to steal your thread here steve but what is the cause of this code "P0440" something about evap system?

 

[98 TGP TOY]

Gas cap is probably loose.

 

[mybluegtp]

Originally posted by 98 gtp toy@Mar 30 2004, 10:42 PM
Gas cap is probably loose.

no that aint it cause evertime i put gas i always make sure the cap clicks at least 3 times when putting it back on.

 

[98 TGP TOY]

Well the codes is for a gas vapor leak in your fuel system. Commonly a loose gas cap. Otherwise you may have an actual leak.

 

[mybluegtp]

thats what i'm afraid of.. do you know how to look for it?

 

[98 TGP TOY]

Well, I read somewhere else you will need to take it to the dealer. They do some type of smoke thing. Pump smoke in somewhere and see if it leaks out. Probably into your gas tank. Also, there have been many times that I have tightened the gas cap and later found it loose. It could still be a leaky gas cap. Check for any wear on it. Maybe a bad o-ring if it has one.