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Post by way2old on Dec 17, 2004 21:04:11 GMT -5
Hi Guys . I got a 98 Crown Vic that had a P0430 bank 2 cat below efficiency. Ran all tests per Ford and replaced converter. Just for good measure we replaced both O2 sensors. Rear was moving same as front before replcement. Now the rear voltage on bank 2 slowly climbs from 0 volts to .9+v and flatlines there. Told tech to check wiring cause I feel there are some wires shorting. He said he did and can find no problem in wiring. Is there anything I am missing or overlooking.
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Post by Venturi on Dec 17, 2004 22:20:23 GMT -5
Damn this post has legs, it gets around. lol
2 questions;
1) What is the pre-cat O2 reading? I assume since you didn’t mention its voltage was staying high too it’s switching nicely.
2) Is it still setting the cat code? The reason I ask is because I’ve had a couple of these that the post cat O2s would stay high after the repairs and they never did set any codes.
3) I know I said only 2 questions but what the hell. Are the voltage readings being taken at the sensor or off the scanner? Might want to take a reading at the sensor if you haven’t already just to be sure your seeing the truth.
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Post by DanD on Dec 18, 2004 6:35:38 GMT -5
Are you sure that it’s not just a green cat, which needs to be in service for a wile before it stabilizes?
On an emissions fail and the cat was the cause, I’ll ask the customer to run the car for a few days, after changing it before I will run the next ASM.
I have seen new cats run as low as 20 % efficient and in one case even produce NOX. But that was because the beds were loaded backwards in the shell. That’s also why I always test them, to make sure I didn’t buy a half-empty can. It only takes a couple of minutes to drill and plug a test hole.
You probably have this formula to test efficiency, but I’ll give it to you anyway. These are Gas analyzer readings, you would subtract post cat from pre divide by pre which will give the % of efficiency. Who knows what they coat the catalyst with during assembly.
Dan.
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Post by way2old on Dec 18, 2004 16:25:25 GMT -5
Looking for all the minds I can find Mike  Thanks guys. The other 3 sensors are normal. Both front sensors switching close to full scale and rapidly. Bank 1 rear switching lazily from approx. .4 to .7. LTFT on both banks at -2. Seems to me that bank 2 should be reading different. There is no code that has returned. The readings are off the scanner. We have tried 3 different ones(NGS, OTC Genesis and a palm based scanner.) Merry Christmas Guys. I will turn up a glass of good Ky. bourbon and toast both of ya. |
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Post by Venturi on Dec 19, 2004 1:12:05 GMT -5
I’m not sure how much affect the post-cat O2 would have on the LTFT in this case. Does Ford use the post-cat O2s for fuel trims on this vehicle or are they just catalyst monitors? I think Dan has a good point that the cat may just be green and needs to be put in service to start working properly. Maybe you should run it through a few drive cycles and see if it will start working more to your liking. Just out of curiosity is this an aftermarket converter or is it OEM? We’ve been bitten by the after market cats once or twice so we only use OEM anymore. Merry Christmas Tom,  I just got back from an oyster roast myself so if the post turns out to be no more than gibberish blame it on the shell fish and alcohol.  Mike |
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Post by way2old on Dec 19, 2004 12:04:07 GMT -5
Well, being the city, low bid takes it. It is aftermarket. My assistant is back Monday and I will drive it a while. See ya. Oh, i saw the "shell" fish and thought it said "smell" fish. Wishful thinking  |
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Post by Venturi on Dec 19, 2004 14:02:00 GMT -5
;D
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Post by way2old on Dec 22, 2004 20:06:36 GMT -5
Well today we looked at this a little more. Found there was 2 wires on O2 that had 12V.(red and a tan/yellow) Checked bank 1 and there was only the red wire that had voltage. Checked bank 2 while bank 1 unplugged and only had voltage on the red wire. Plugged bank 1 in and only red wire had voltage again. Started vehicle and O2 worked perfectly(horray) for about 3 minutes. Then it dropped to 0 volts. Unplugged both sensors again and voltage was the same. Plugged back in, started vehicle and bank 2 went straight to .9V and flatlined. So, i am still inclined to believe this is a wiring problem. Found only one place, besides PCM where they are together. We will play more and keep you posted. Oh, Mike. I will not post elsewhere till there is a definate fix. And Dan. We drove it for over an hour 3 times and no change. See ya.
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Post by DanD on Dec 24, 2004 0:10:20 GMT -5
Looking at a Mitchell wiring Diagram (as much as you can trust them) the red wires are the heaters 12V feed for both the rear O2 and that seems to be the only common between the two, for battery voltage.
The tan/yellow wire is the PCM control wire for O2 bank 1 rear heater. That’s where I don’t, know if my diagram is the correct one or I miss read your post that this Tan/Yellow is on bank one sensor two?
Either way there has to be an intermittent open or short to power on that Tan/Yellow circuit, there should never be voltage on that line (while back probing) unless there isn’t a path to ground or a short to power. Like you said in the wiring,PCM or who would ever think a defective O2s heater shorting to power. (Does the heater circuit time out?)
With some of the other things you mentioned, it wouldn’t surprise me if Fred under the dash weren’t starting get a little brain dead.
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Post by Venturi on Dec 29, 2004 20:30:11 GMT -5
Did you ever get this figured out Tom?
I’ve been out of town for a few days so I’m a little behind (actually being a little behind is normal for me, I’m way behind now). lol
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