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Discussion Starter · #1 ·
Hello Fella's ...

Happy Thanksgiving .......

So I have been stuck in the same situation with my car. If you recall, I managed to fix all the DTC/MIL codes thanks to your help .... at this point I still cannot pass emissions as my reader faults the EGR/CAT/O2.

To date, I've changed out the EGR valve and solenoid, along with all four O2 sensors . I partly did the O2 swap because I had the headers recently coated inside/out and wanted to be sure that something else inside hadn't somehow messed with them. I had to be under there anyways and for the cost and little time, I thought it would also eliminate one variable. I also cut out and welded in a new passenger-side CAT. I picked up a constant rattle and every time I looked in that area it was coming from (where the heatshield or that CAT was) I couldn't find any other culprit so again, tried to remove two variables. I removed and added heat-shielding/padding in between the heatshield and body and as mentioned replaced the CAT. Despite all this and now 300 miles of driving, the emissions faults are not clearing.... I think the only thing thats not new is the driver side CAT. Car only has 115K in miles so perhaps its conceivable that both CATS were in need of replacement but who knows.

So anyway... posting here to source out any ideas before I call "no joy" and have a mechanic look at it. I always want to solve myself, so I can learn but after all the work I have done to get it this far, along with enjoying driving her again, I dont want to lose any more time....

Thanks for your help.

Jorge
 

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1993 6-spd T/A - 1996 C4
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Are you following the diagnostic flowcharts in the Factory Service Manual for these codes? ...if not, download it and do it right. No guessing.

 

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Discussion Starter · #3 ·
Hello .. and thanks for the response ... I guess this is where I am stuck. Based on my scanner, there are no codes .. no MIL or DTC codes .. no service engine or check engine light .. All my scanner is currently showing are the emission faults mentioned above, which is preventing it from passing smog.
 

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Have you done a running sensor scan with your scanner. It could show you where the problem lies. If you don't have a scanner that does running sensor scans, go buy one.

If you haven't a clue what sensor reading are showing you, let me know and I'll post the pdf file " scanner readings and what they mean". Written by our member Injuneer.

Also, be aware that not only the sensors can cause faulty readings. So can wires, connectors, grounds, power feeds, & splices in the wire.
 

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Discussion Starter · #5 ·
Hello .. thanks for the insight/help .. I have an old Craftsman scanner and honestly not sure if it does or does not.

So in response to your second point - nope .. I have no clue but very willing to learn and understand so yes please post/send the .pdf file. It will help me know if my scanner can do it or not and then direct me to the correct scanner to get ...
Lastly good points. ... your third comment... I had not been thinking about all the other elements involved....

in any case... thank you ....

Jorge
 

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Have you done a running sensor scan with your scanner. It could show you where the problem lies. If you don't have a scanner that does running sensor scans, go buy one.
While troubleshooting my fake MAP failure, I also read that you could read the raw sensor values. Is this what you're taking about?

What kind of a reader would do this? the one I have only reads the codes. I looked around a bit on Amazon but nothing clicked for me to say that particular scanner reads raw codes.

What scanner is good for this?


If you haven't a clue what sensor reading are showing you, let me know and I'll post the pdf file " scanner readings and what they mean". Written by our member Injuneer.
If you could post it, please do. would be good for me too.

thanks
 

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Discussion Starter · #7 ·
Hey Guys .. for those keeping score ...

I just managed to drive my way past the EGR emissions indicator .... now down to two ... O2 and CAT ....
 

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Discussion Starter · #8 ·
At roughly the 800 mile mark, I have cleared the CAT emissions failure ... leaving only the O2. I hope they are sequential so that now that the CAT is clear, it will make it more likely that the O2 will clear. Regardless I believe I can now pass my smog test, which I will attempt in the next few weeks.
 

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Discussion Starter · #9 ·
Ok .. well I think the near term end is near. I was able to find a smog service station that was not afraid of my car. The guy I had gone to for my other cars would not even attempt it.. One look at my Canton valve covers and he was calling them a questionable performance mod. Despite me telling him that the headers are CARB legal... my cats are in the stock location ..etc... he said nope... So I reached out to the mechanic I tasked with checking the scan readings and sure enough the guy he sent me to passed it. I mean it passed all the checks on its own .. he did manufacture an outcome but as he said when I was paying .. todays smog guys/mechanics dont understand old cars. So with that .. smog certificate is at the DMV and in a few short weeks I hope to be street legal....
 

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(y)
 

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Discussion Starter · #11 ·
Hey Guys .....

so as some may know ... I was able to get my car to pass smog and registered. Its been just a few months so I decided to hook the scanner up to see if the last one - O2 emissions fault code had cleared. I'm at the roughly 2K miles and figured by now it should. Well it hadn't and with I checked the DTC/Mil codes a P300 popped up. I cleared it and continued to run it. This was about a week or two ago. Today, I checked again and no P300 but all three emissions codes - CAT, O2 and EGR are flashing incomplete. Now I am 99% sure my BCU is bad - radio goes on and off .. windows selectively work ... etc. Is it possible that the BCU is causing this? It just all seems very strange because otherwise she runs great ...

appreciate your thoughts and suggestions..

Jorge
 

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DELCO NERD
1993 Pontiac Firebird Trans Am, LT1 5.7L V8
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The Body Control Module (BCM, or as you referred to it, "BCU") is the most likely culprit of your radio and power window malfunctions, but it has nothing to do with the "P" codes stored in your Powertrain Control Module (PCM).
 
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Discussion Starter · #13 ·
yeah i figured as much ... whats really got me baffled is the fact that the two emissions failures returned, when they were once clear - CAT and EGR. The O2 has not reset itself to date...
 
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