So I fill up my tank and drive, and when i get to about 3/4 of a tank (100 or so miles) my CEL comes on, when i check it, it says code 64.

Catalytic Converter Efficiency Failure...

Amazingly, when i get down to a 1/4 tank or less, the light goes off. But whats interesting is that, I passed emissions with flying colors, they thought the car was brand spankin new. (well the engine is) The converter has 122,000. Whats up? Should I go buy a new one?

 

downstream o2 sensor reads the emitions from the cat it runs in cycles you just hit it at a point between reads that why the cel goes off. they dont check emitions in your state? here in NY they hook to the odb2 port and scan the engine 96 and newer so i had to replace the cat and the o2 sensors

 

I PASSED EMISSIONS. The light wasn't on when i went, but it was like 10 minutes before. If there was a problem with the o2 sensors another engine code would come on though. I think its 21 or something. Anyway, I was just wondering if it was something eletrical... like you said when the o2 sensor reads. Cause there shouldn't be anything wrong with my cat, i had very very low emissions. I guess i'll just look at getting a new cat and new sensors.

 

i cut my cat out a while back and my cel light has been on since like day 2, it goes out when i take the pos battery cable off, and about 50 miles down the road it pops back on, is there a way to make it not come on because there is no cat? how do the header kids do it?

 

If I am correct the reason your check engine light is comeing on is because your O2 Sensor isnt picking up any readings from the cat, there fore your PCM is setting off the check engin light, thinking that your O2 Sensor is bad. The only way that I know of making the check engine light go off is putting back on the cat. You could be able to shut the light off useing a OEM II code reader or whatever its called.

 

well there is lots of things u can do to make the light go off one thing u can do is ground the wires..you can always put electrical tape over the check engine light...also take out the check engine light bulb.....with the o2 sensor reading soo high ur is probly running worse if u ask me it should idle wierd and when u flow it it should be real slow....the o2 sensor is telling the pcm to run rich.....

 

No one does OBD-2 port scans on 1995 cars, even ours, which have OBD-2...

Casper's Electronics sells O2 simulator plugs.

The test for cat efficiency requires certain conditions to run. Mine would only come on after a longer trip on the highway. I passed the sniffer test with chunks of the cat rattling around inside...

 

not having the cat can make my car idle funnny???? if so that could be my idle gremlen!!!!!! bah
Thanks!

 

ive had a header on my car for a few years now and the check engine light has never been on for an o2 sensor or the cat.

 

If you have a '95 Neon and a Mopar PCM, you'll never get any codes associated with the downstream O2 sensor, even if the cat is completely removed and the O2 sensor is disconnected. If you have a '96-up, the downstream sensor has to be connected (or a sim plug used) or you'll eventually get a CEL, even with the Mopar PCM. If you have a '96-up with the Mopar PCM and have eliminated the cat, but still have the downstream sensor (or sim plug) attached, you may never get a cat efficiency code because the tolerance is greatly expanded. A shorty header with a cat attached, and a d/s O2 sensor (or sim plug) isn't going to trip a CEL.