Recently purchased a 96 with a 383, upgraded exhaust but left cats and tune. In short I am failing the Texas emissions test because I have 3 sensors in a "not ready" state. With a 96 I am allowed 2.

Ready Sensors:
Misfire
Fuel system
Comp Cmpnt (not sure exactly what this is)
Secondary

Not Ready:
Catalyst
O2 Sensor
Heated O2

I have completed the GM Drive cycle several times on different days to ensure a cold start. I can not get any of the last 3 to flip.
Does anyone have any ideas?

I was told the original owner wanted to ensure it would still pass MN emissions testing. I was going through a stack of receipts and I noticed a new tune was done in 1999, the 383 was done in 1997. I googled MN emissions law and it went away in 1999. So I am starting to suspect that tune turned off those sensors.

I am going to reach out to Doug Rippie Motorsports today as they did all the mods and tune and see if they have any info for me. But not sure they will remember what they did 18 years ago. I also plan on stopping by an engine tuner in my area on the way home today and see what they have to say.

Guess I am hoping someone has some ideas before I end up paying for a new tune, and hoping the ECM is not locked.

 

Does the car still have the O2 sensors in place?

 

I assume so as if they were just removed I believe I would have a check engine light vs tuning ecm to ignore them no check engine light.

I do know there are no Codes present.

But to answer your question I have not physically crawled under to verify they are there and connected because of my assumption above.

 

It could be as simple as the O2 sensors being bad. If the rear sensor is bad, it will not think the cat is working properly, so that would account for two of the three by itself. First step might be to replace those sensors.

FWIW, you can tune that PCM with Jet DST software. You can also set those tests to any condition you want with that app, including "do not report." It's not cheap software, but it is effective.

 

If the sensor was bad would I get a check engine light or just not ready?

Cost of software is not what really scares me, screwing something up on the pcm is what scares me. I do plan on trying to talk to tuner today about this, just not sure how cool it is to talk to a shop about that.

 

I have lived in TX for the past 24 years, and I've never had to pass an emissions test (with any car). What is it?

 

96 and up, and the big city counties. I live in Collin County, Dallas suburb. I next city north of me is a non-emission county. Yeah for me .

But since I live in Collin I HAVE to pass somehow can just drive north unfortunately.

 

I'm just lucky, then, Bexar County, plus my C4 is an '89...

Steve

 

Well I spoke to Doug at DRM and he remembers the car I guess being 1 of 2 Grandsports they put a 383 in makes it easy to remember, he confirmed they turned off the sensors. So the good news is I know what the issue is the bad news is I get to try to find a tuner to fix it with out bricking my ECM or messing up his tune.

 

Turning off the sensors could be the cause, but I would have expected that they set them to "do not report." If they turned off the front O2 sensors, then I'm not sure how the car would do any closed-loop calibrating. I'm not sure I buy that. The front sensors should be turned on and reporting. If they are not operating, it may or may not set a code. But I don't think there is a code that says "O2 sensor bad." It just tends to show codes like "rich condition bank 1" or something similar.

It would be difficult to brick the PCM with Jet DST (that said, there's another thread currently about just that). All you'd be changing is the settings for the cats and rear O2 sensors. If the car runs well, then there is no reason to change anything else. Basically, as long as the car has a charged battery and the laptop also does (or is plugged in), the flash process is pretty straightforward and only takes a minute or two.

 

A lot of tuners, Rippie And LPE were known for burning open loop only chips. That way they did not have to deal with the fine tuning for drivability standards. It was a fat time and protected their work and lessened the warranty claims.

 

Wow. Well it may be time for the OP to start from a factory tune and do a better tune than they did!

 

I'll admit I'm not super knowledgeable in the tuning world. I have read plenty of threads about the sensors being turned off and car runs fine off rear sensors. I've also seen the other thread about the pcm getting bricked, plus many more researching this issue.
Doug made it clear the sensors are turned off and not masked to say ready or do not report. And they are not in use in anyway. I do know it was a dyno tune not just a chip.

 

FWIW, the only thing the rear sensors do is determine if the cat is doing what it should. I don't think the engine references them for any fuel/spark calibrations at all. Maybe they left the rears on so as not to set any lights? And I guess this was before the days of plug-in scan emissions testing? Because in this condition the car could never have passed that test. Did they only set up the two 383 cars to run this way, or a bunch of them? Because if the latter, there should be more people with your problem.

So the car will run well enough in its current always-open-loop condition. And on the dyno it would surely be very tunable, since even stock these cars run open loop at or near full throttle. It just seems like it wouldn't be running ideally well at low loads and throttle openings. It will run - don't get me wrong. But fuel economy and emissions will surely suffer.

Re why they didn't set them to "do not report," it is possible that capability wasn't available in tuning software in 1999. That would have been Tunercat back then.

So the bottom line, though, is that you can pass the plug-in emissions test by using Jet DST to set those tests to "do not report." If that's the only change you make, it won't make a bit of difference to the way the car runs. The only other tuning software is LT1-Edit, but I am not certain that it can turn these tests off. I've never used it.

 

I do not know how many 383 they did. I know they only did 2 grandsports. One had the original motor modified and mine had the original motor pulled and put on an engine cradle and a new lt4 was sourced and modified. This issue isn't common in the c4 forum because 96 was the first year of obd2. Doing a search reading on my issue will pull you into the c5 forum a lot. After reading many threads I was 99% sure it was just turned off just wanted to confirm.
In 1999 MN removed all emission testing that is when the last tune was done. My guess is they didn't either have the option to do do not report or a false ready then or they just didn't care since it was a non issue in MN.

 

I will say it runs damn good at idle to full throttle. According to the on board fuel mileage at 55 with cruise control on it was getting mid to high 20mph. It was drinking gas when I drove it hard though.

 

Yep, we 96 owners have bastard-child cars. It's annoying because none of the typical and well supported modern tuning software works on our cars. I am actually currently running a 94/95 PCM in mine, mainly because it supports a complete locking of the Block Learn module. But I have to put my 96 PCM back in to pass emissions. Even my 396 with lots of cam overlap gets 26mpg on the highway. They all drink gas at WOT.

 

I have been thinking about swapping the computer in my '96 to a '94-'95 one so I can tune it like my '95 with some of the Moates stuff.

Is it a direct swap so that all needs to be done is flash the correct tune for the car? Or is anything else involved?

Thanks.

 

My experience is that it is a direct swap. You will get an intermittent "sys" light on the dash because the CCM expects a different computer. And of course you can't pass a plug-in emissions test. But otherwise they work as plug-n-play.

 

Talked to a local tuner said he is familiar with Doug's tuning was surprised when I said he still answers the phone at DRM. Said as long as the ecu isn't locked he thinks he can adjust the sensors. I am bring it by after work today for him to just plug in and see whats there. So should know next step today or maybe "fixed".