P0420 97 ranger

Troy

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#1
97 ranger 4.0. A little background first. The Truck was throwing lean codes. Turned out to be leaking intake gasket. Changed the gasket Fixed the lean codes. Now it's throwing P0420 (Catalyst System Efficiency). Another symptoms is when the truck is started "sometimes" you can hear a rattling noise from underneath the truck. I haven't been able to pinpoint where the actual rattling is coming from yet. With the P0420 & rattling noise my first guess is a bad converter. Would like to get you suggestions. Thanks!

Troy
 
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#2
please post the code you got with the 'lean' problem...

as for rattling and a cat code I agree the cat sounds suspect: BUT they are not cheap so troubleshoot the system before throwing parts at it.... A good article by on of the techs here may help

http://www.batauto.com/articles/catfailure/
 
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#3
"I haven't been able to pinpoint where the actual rattling is coming from yet."

What was your method? I like to strike the exhaust with something big and soft, usually my foot. If it rattles, I get my head near to the exhaust and strike it with my palm, or a plastic or rubber mallet.
 

Troy

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Kev2: The lean codes were p0171 & p0174 with p0300(random misfire). Changes fuel rail gasket, codes haven't been back in months. Thanks for the link to the article.

Danica: As for checking for the rattle. I'm waiting to catch it when it's rattling & listen with a stethoscope.

Another thing I think I should point out that I think is very strange. My code reader/scanner in live data shows the fuel trims all at -100 & all o2's at 0volts. Scanner works as sees these readings fine on other cars so it's working correct. Why the strange readings? Could all three o2's be bad?

Troy
 

Troy

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#5
This is the freeze frame data for the p0420 if he it helps.
Closed loop
Calc load 32.5
ect 192
STFT B1 3.9
LTFT B1 4.6
STFT B2 1.5
LTFT B2 .7
RPM 1897

Like Kev said I hate to spend money on a conv & not be the problem. I still don't understand why my scanner, I guess I should say code reader shows the weird reading "see my previous post" in live data mode. Do the Freeze frame Fuel trims show you anything?
 
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#6
what we want to look at is ox ygen sensors o2, locations s1 and s2 - if there is a 0volt reading on both (should be moving and @.2 to .9) might want to inspect o2 senssor wiring- pluged in damaged etc... definately a reason to suspect sensor BUT both failing at same time unlikely.....as the system should throw a p0151...

a quick test - we could force a changing reading by sprying carb cleaner into engine - the o2 voltage should increase as it sees the rich condition

AS you were able to retrive freee frames you scanner should read o2 voltage, live data or PIDs
 

Troy

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I haven't forgot about the thread. I was waiting for the I/M monitors to complete. The only thing I did was unplug & plug the rear O2 sensor. Cleared the codes (P0420). I've been waiting for the I/M monitors to run & complete. I check this morning & All I/M monitors have run & all is clear. Have a green Light & no codes set. Hmm! I'm still baffled as to why the Fuel trims show -100 & O2's show zero volts in live data mode? Has anybody came across this before or have an idea why?

That's where I'm at know. If the p420 come back I guess I will have to try to manually check the O2's. I know it's been a few days just wanted to update you. Thanks
 
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#8
what is interesting is that scanner shows no 02 activity zero volts, in theory if the PCM were to see no movement or zero volts it would set a code.... p0131 p0133... might want to liik at pending codes... otherwise maybe another scanner to confirm... but still thinking on this
 

Troy

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#9
Kev2:

Yes it is strange indeed. I don't know if it's a some compatibility issue or what. I'm going to try to see what tech support has to say about these strange readings. I'm also going to try out a different brand scanner too. As far as I know still no codes or CEL. I will let you know what I found out.

Troy
 

Gus

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#10
Try Autozone....they will attach their scanner for free, and look at their data....
 

Troy

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Wanted to give another update to the the strange fuel trim & o2 readings on the scanner. I made a call & email to tech support for the scanner. Asked why in live data the fuel trims show static -100% & o2's show 0 volts. Two different people & I got two different answers. One said the scanner drops the feed on some of the older cars. The other didn't know why it was showing it like that. So they really weren't much help.

I tried a different scanner & hooked it up. Fuel trim -100% & No O2 readings. The same thing! I think if these were true readings it would have thrown some type of code. I have an email into there tech about this too. At this point I'm thinking it's a compatibility type issue. Haven't confirmed yet though. No one has ever came across a vehicle with the strange live data readings?

I'll let you know what I find out.

Thanks!
 

Gus

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#13
I agree with Kev2....don't know how the O2 flag can reset and not cause a code with those readings....
 

sunny

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#14
Check the O2 outputs with a DVOM at the sensors and see what they are actually doing.
 

Troy

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#15
Danica: The O2's are not universal.

I do plant to test the O2's with my meter. My gut tells me there working & not a static 0 like the scantool reports.

Something I just found out! No where on the emissions label (veci) does it say OBDII certified/compliant.