1996LT1Z28

I'm pretty sure that these catalytic convertors are the original to the car - 1996 Z28.

After all these years, are they still any good or just toast?

I'm thinking I'm going to need to replace them.

Any suggestions?

Injuneer

Do you have recent emission test results that indicate they are not doing their job?

1996LT1Z28

No....just the OBD2 scanner is telling me that the emission staus is in the red.

I'm going to replace the O2 sensors and see what happens.

Injuneer

"Emissions" covers a multitude of systems. Does the scanner show any codes? How does it tell you "emission status is in the red"? Is it referencing the "ready" status of one or more of the emissions systems?

Jeffs1997

I bought a 97 z28 with 122k miles, smoged it and it passed california emissions with ease. So yours are probably still ok.

1996LT1Z28

[QUOTE=Injuneer;6950424]"Emissions" covers a multitude of systems. Does the scanner show any codes? How does it tell you "emission status is in the red"? Is it referencing the "ready" status of one or more of the emissions system.

My scanner has three LEDS that tell me what state the emission system is in...Green = Good, Yellow = Medial Operation, and Red = Bad emissions problem.

No codes either, which is why I'm thinking the O2 are bad.

This thing is burning gas like there's no tomorrow.

This car is driving me nuts!!!

Injuneer

But WHAT "emissions system"? You have EVAP, AIR, EGR, Cats? Do you have a manual with the scanner that explains the function of the LED's? What is the make and model number of the scanner. I've been helping people data log, and interpret their results for 15 years, and I've never come across anything like what you are describing.

The only actual "emissions" that are monitored are indirect, being the oxygen storage capacity of the catalytic converters. The PCM compares the range of voltage swings on the after-cat sensors to the range of voltage swings on the pre-cat sensors. If the results fall outside the acceptable range, you would have codes P0420 and/or P0430, but you indicate you have no codes.

If it's running rich, could be caused by a "false" lean reading on the O2 sensor(s). This could be due to misfires, exhaust leaks before the pre-cat O2 sensors or faulty pre-cat O2 sensors/wiring.

Mr99SS

if u do have to replace the cats go with random tech... I have them on my 99 Camaro and 06 tbss they flow a lot better also .

bad 02 sensors will make it use a lot more fuel. that's how the ecm tells weather it needs more fuel or not. but im sure you know this

1996LT1Z28

Injuneer:

I'm using a Craftsman 87702 OBD2 scanner. If you have the time, take a look and let me know what you think. I wish it communicated with the Air Bag Module. I need to troubleshoot that too.

Thanks for taking the time to help out. I'm used to my 69 Camaro SS...way easier to work on!!!!

Injuneer

Here's what the red LED indicates:

Since you indicated you do not have any codes, it means "there is a problem in one or more of the vehicle's systems." Doesn't tell you which one. I suspect it's telling you there is something that may not pass a computer based emissions test. One of the emissions control systems is "not ready".

There's no way you can extrapolate that to a bad cat, or a bad O2 sensor, or a bad anything else.

The yellow LED tells you there are "pending" codes.... these are codes that have set, but not frequently enough to become active codes.

The description for the green and yellow LED's would appear to be pointing to the same conclusion - you have an emissions system that is "not ready"... the PCM can not run diagnostics on that system.

Here's the rest of the description:

nikko

I know this is an old post but my 96 z28 has a check engine with a code for a catalyst problem. Took the car to muffler shop and lo and be hold previous owner had drilled and emptied cats and rewelded .Now I 'll never get my lights off ,Any suggestions by the wy the code is P0430

GaryDoug

Suggestions in descending orders of expense and "the right thing to do":

1. Replace the passenger-side cat. Driver side is probably not far behind.

2. Buy and install a couple of the many devices used to trick the PCM into thinking the CATs are ok.

3. Put a piece of tape over the SES lamp in the instrument cluster.

Injuneer

You could also have a mail order programmer "program out" the codes for the after-cat O2 sensors (P0420, P0430).

nikko

mail order programmer??? You lost me injuneer

Injuneer

You mail your PCM to an experienced tuner. They can delete codes, while not causing a "system not ready" flag to set. They can also do things like change the rev limiter setting, change the top speed limiter, alter the shift points and firmness on an automatic, lean out the WOT target A/F ratio for a 10-15 HP gain, etc. They program the PCM and mail it back to you.

They could also do a tune file and e-mail the file to you so you can load it into the PCM.