Check Engine Light, ETS OFF, P0420 - Maintenance and Repair Forum

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Check Engine Light, ETS OFF, P0420
Saturday, February 25, 2006 5:05 PM
Been a chevy man for a while now and have had my Z28 for about 3 years - I know that thing inside and out. However, I just picked up a 97 cavalier LS 2.4 and am not too keen on what's going on with it. I have the oh-so-familiar Check Engine Light along with the ETS OFF and two of the same code P0420 Catalyst Efficient Below Threshold Bank 1. I originally had a misfire code so I had a tune up done that was supposed to take care of the it. For the P0420 code, I had the rear 02 sensor replaced as the mechanic was pretty sure it wasn't the cat malfunctioning. After they did the work, they put it through Emissions and it passed. I was happy... except the lights keep coming on now. The only thing I can think of if the 02 was replaced is that the cat is bad, but then it wouldn't have passed emissions I have no idea what's going on here. Maybe I'm just chasing my tail and it's something else? I've heard that if you don't screw the gas cap on tight enough then this light comes on, but I've made sure multiple times that it's on correctly (after taking it off and letting all the fumes out to make sure). Like I said, I'm new to the cavalier game but would like to get this figured out as it's a recurring thing. Thanks in advance for all the help guys.

Re: Check Engine Light, ETS OFF, P0420
Saturday, February 25, 2006 7:45 PM
I had this problem when I installed an aftermarket air intake and didn't get the o2 sensor plugged into it. It made my auto shift hard too.

Rob




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Re: Check Engine Light, ETS OFF, P0420
Saturday, February 25, 2006 7:49 PM
There is no O2 sensor in the intake, only pre-cat and post-cat O2's and they are both plugged in.

My whole problem with this thing is that it passed emissions which are stringent where I live. It's gotta be something simple.
Re: Check Engine Light, ETS OFF, P0420
Saturday, February 25, 2006 8:55 PM
what kind of sensor did they replace it with? hopefully AC delco and not bosch have you replaced the on in the header yet?




Re: Check Engine Light, ETS OFF, P0420
Sunday, February 26, 2006 9:49 AM
I have no idea what brand of sensor they replaced it with. The only sensor replaced was the post-cat sensor, not the one in the header. I wouldn't think it would matter what brand it is.
Re: Check Engine Light, ETS OFF, P0420
Sunday, February 26, 2006 10:51 AM
Yes it does matter, GM cars are designed to run with delcos (comes from the factory) if there is anything else the car's computer will not like it and the car will run like @!#$. I know for a fact that if the car is not modified preformance wise you should stick with stock parts (delco).

Check the O2 sensor to see what it has been replaced with if its not delco throw it out!

As for the ETS the computer turns off the traction control system if there is a problem with the engine emissions system (check engine light).
Re: Check Engine Light, ETS OFF, P0420
Sunday, February 26, 2006 11:02 AM
Hm, good to know about the Delco parts. Also, good to know b/c my uncle is a Delco parts distributor I am familiar with the ETS turning off whenever there is a check engine problem, great design by GM. I'll check into what sensor they replaced it with. It would be nice if this simple fix solved all the problems!
Re: Check Engine Light, ETS OFF, P0420
Sunday, February 26, 2006 2:32 PM
I think redgote meant the iat sensor in the intake.







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Re: Check Engine Light, ETS OFF, P0420
Sunday, February 26, 2006 9:08 PM
Can anyone else verify the car not liking non-Delco parts? I just want to make sure before I make the shop swap it out.
Re: Check Engine Light, ETS OFF, P0420
Monday, February 27, 2006 12:03 AM
yea, for some reason the bosch o2 sensor does not work on cavs. get the ac delco one and it should solve the problem. my old 96 z24 had the same problem. went thru like 5 bosch sensors before i figured it out. they also sell a slotted socket that makes changing the sensor alot easier...
Re: Check Engine Light, ETS OFF, P0420
Monday, February 27, 2006 6:41 AM
soul horse wrote:I think redgote meant the iat sensor in the intake.


Yeah thanks that is what I meant.

Rob




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Sold 2/2/05

Re: Check Engine Light, ETS OFF, P0420
Monday, February 27, 2006 8:05 AM
Thanks a lot guys, I'll try that!
Re: Check Engine Light, ETS OFF, P0420
Monday, February 27, 2006 9:42 AM
I've had NO problem with the replacement Bosch after-cat O2 sensor I put in my 96 Sunfire, 2.4, 4spd. auto. After replacement, It even fixed my ETS light after I cleared the code. Make sure the base of the O2 sensor is fully seated, tight, and in contact with the bung. If not, I've heard the code will reoccur. Good luck and let us know how you make out.
Re: Check Engine Light, ETS OFF, P0420
Monday, February 27, 2006 9:46 AM
Jay 2K2 Sunfire GT wrote:... they also sell a slotted socket that makes changing the sensor alot easier...


goto Autozone

they'll rent u that special oxygen sensor socket set for free

while u r there... have them reset the car's computer w/ the obd II scanner...

drive along & see if the check engine lights up again... then go have them read the codes...

if it's a bad cat/ then it's still under warranty, i believe...
Re: Check Engine Light, ETS OFF, P0420
Monday, February 27, 2006 10:07 AM
after your done take the posi and neg off of the battery and put them back on, that should make the dummy light go off.
Re: Check Engine Light, ETS OFF, P0420
Monday, February 27, 2006 10:40 AM
I've had the codes reset, however they keep coming on after the replacement of the O2 sensor which is why I'm confused as to what's going on. Now that someone else has chimed in that they've replaced theirs with a Bosch and had no problems, it confuses me even more as to what the problem is. I'm not worried about getting it fixed b/c I'll just keep taking it back to the shop that was supposed to fix it. However, I'd like to get to the bottom of it so I can stop taking it back there and playing a guessing game I also don't want to have to invest in a cat if it's working properly and the problem lies somewhere else!
Re: Check Engine Light, ETS OFF, P0420
Monday, February 27, 2006 12:29 PM
the shop can stuff their exhaust gas analyzer & rule out a bad cat in minutes... y r they guessing?
Re: Check Engine Light, ETS OFF, P0420
Monday, February 27, 2006 1:00 PM
They're not guessing. The car passed emissions, therefore the cat is ok in terms of emissions control (not necessarily on the electrical side though). The guessing game lies within what sensor is causing this problem, whether it be a faulty sensor, something the car doesn't like, or that something is actually wrong with the emissions other than the cat.
Re: Check Engine Light, ETS OFF, P0420
Tuesday, February 28, 2006 3:28 PM
just get the ac delco sensor...
Re: Check Engine Light, ETS OFF, P0420
Wednesday, March 01, 2006 11:42 AM
Oxygen sensors: Most are equipped with the OBD2 management system which employs two oxygen sensors if the first one isn't sending a code then it's after that were your having problems exhaust might be leaking (clamp, flange, hole,) the cat could be gummed up but still work but still set off the o2 A code that is set off doesn't tell you what part needs to be fixed / replaced just a general idea of the area you need to be headed yes sensors fail but when they do work they tell ya something isn't going the way it should alot of people get this code people in the snow belt areas drive there car the cat / mufflers heat up and drive thru snow The snow hits the red hot cat causing the cat to expand and shrink 20 times a day the cat could have a split in it a pipe could have a leak? Water does this aswell (Rain puddles) take a look at the exhaust system first before buying #3 o2 sensor

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Re: Check Engine Light, ETS OFF, P0420
Wednesday, April 02, 2008 11:44 AM
Any more updates on this? I am just experiencing the same symptom on a 97 sunfire 2.4. The car has been sitting for a while. At 1st both were on and the code was random misfire. The after driving it for 30 miles both just went out. Now all of the sudden on they both came on this morning. The thing runs out good. Going to read the code tonight.

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