Error Code P0420 on 97 Chev Cavalier

[selee]

I have a 97 Chev Cav Z24 and the check engine light is on. It is failing e-check because of this. I took it to AutoZone and got and error code P0420. Does anyone know what I need to do to get that check engine light off? The car is running fine. I have to get the car e-checked to get my tags renewed and I am running out of time and I don't really have much money for a repair. All suggestions would be greatly appreciated.

[Classicrocjunkie]

Disconnect the battery for 30min and that will "flash" your computer... that should get rid of the error code.. but if you keep gettin the check engine, you need to get that fixed..

[selee]

We already tried that. Amazingly enough, over the weekend the check engine light just went off out of the blue. So, we are going to get it to e-check and hope it passes. It all does not make sense to me. The light has been on for 3 weeks and all the sudden it goes off.

['94CavyRs3.1]

probably just a bug in the system that needed to be worked out? or a lose connection that sent a faulty error?

[selee]

Well, the check engine light is back on. So I guess I am going back to autozone to have the code read again. Hopefully I can find out what the problem is. I only have 5 days before I have to get my tags.

['94CavyRs3.1]

good thing Wisconsin dont have any emissons test and what not..have of the cars/trucks would not pass it.

[5150cavy]

P0420 is a Catalyst System Low Efficiency code. Gm's service procedure says to check ur exhaust for leaks and make sure ur rear o2 sensor is not damaged and working properly. if this checks out ok then to replace the cat. converter. If ur just trying to pass emissions u could remove ur rear o2 sensor, tie it up underthe car and plug the hole, then disconnect ur battery to reset the light this should make it think that the cat is working properly. Good luck

[Moody Blues]

I've got the same problem w/ my wife's 97 Cavalier (too wierd) It give a code P0420 and if you clear it, it takes "about a week" to come back. I cleared it just before we drove from San Diego to Big Bear (about 350 miles round trip, on I15, high speed and low speed mountain runs, and some city driving) It runs beautiful, but the check engine light came back on just as we got home from the trip. Code P0420 again, cleared right now and waiting for it to come back on.

I ran a voltage test on the rear O2 and it was in specs but jumped around a lot, the Haynes manual said it should be pretty steady. Also we did find that the rear O2 sensor had come loose, and retightened it into it's hole.

Any ideas?

[wannablast]

You can only clear the codes on OBD cars with a code scanner. The O2 sensor cost about $90 and the wires are not difficult to route.

[sumibadappa]

Hi,

Mine is a similar problem. Check engine light is on and the echeck guy said it would fail anywasy and asked me to get it checked. Took it to car dealer n he asked me to replace CAT and Sensors.I cannot afford that just to get the test passed as the car runs fine. Please tell me how to disconnect battery from the car for 30 mins so that i can do that n take it for echeck. Please respond. Car type:2000 mercury mystique.
Please email to [email protected]

Thanks

[pyro4329]

Heh, I work at Autozone and see that one quite often...

As far as I know, its just a pain in the ass code not affecting much in way of the car running properly. Also know as the dreaded 420 code in the VW Jetta world. There is a simple fix for it, but I don't know if it will pass emission testing. At Autozone and most automotive retailers, there are these spark plug defoulers. I need to find the part #'s but they thread into the o2 bung behind the cat and keep the sensor out of the exhaust flow a bit but enough to still read it, thus preventing the code from coming back up. You have to drill the hole bigger in the defouler to let the gasses reach the sensor still though but it's a quick fix and you can remove it come emission testing time to pass.

[drindle]

Originally Posted by sumibadappa

Hi,

Please tell me how to disconnect battery from the car for 30 mins

umm...step 1: disconnect positive battery cable from battery....
step2: wait 30 minutes (watch the simpsons or something)
step3: reconnect battery cable.

[Lances133]

Originally Posted by drindle

umm...step 1: disconnect positive battery cable from battery....
step2: wait 30 minutes (watch the simpsons or something)
step3: reconnect battery cable.

Actually step 1 should be to post in the mercury mystique forum


But either way -

P0420 OBD-II Trouble Code
Technical DescriptionCatalyst System Efficiency Below Threshold (Bank 1)

What does that mean?Basically this means that the oxygen sensor downstream (after) the catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

SymptomsYou will likely not notice any drivability problems, although there may be symptoms.

CausesA code P0420 may mean that one or more of the following has happened:

Leaded fuel was used where unleaded was called for
An oxygen sensor is not reading (functioning) properly
The engine coolant temperature sensor is not working properly
Damaged exhaust manifold / catalytic converter / exhaust pipe
Retarded spark timing
Possible SolutionsThe simplest thing to do is to reset the code and see if it comes back.

Next step is to measure the voltage at the oxygen sensor on Bank 1 (the rear sensor, or the sensor after the converter). The voltage should be low and steady (~200mV, depends on the vehicle). If the voltage varies (e.g. 100mV to 600mV) then it's time to replace the catalytic converter. In fact, it would be a good idea to test each oxygen O2 sensor while you're at it.

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.

[sumibadappa]

Thank you for all your suggestions. I did look into the warranty from ford on catalytic converter.It says 80,000/8 years. But my car is on 85,000 though its a 2000 year.
So i might want to first reset the code and if it comes back then i will might try the spark plug fix temporarily just to pass the echeck.

Thanks again!