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P0420 and P0430

8

8000RPM

CEG'er
Joined
Jun 21, 2005
Messages
328
Location
Washington, D.C.
i did a search in the archives and it seems like these codes claim that the PRECATS need to be changed, right?? well, why did i get both codes at the same time? i mean, what are the chances that they both went bad at the exact same day? what else could trigger both 02 monitors to give these codes?
 
I took off an cleaned the egr tube about 2 months ago. the TB and the EGR passage in the intake manfold is also clean. egr valve is about 1 year old, works fine. DPFE sensor is 4 months ago...so i doubt if it is the egr.

so what exactly do you mean by IAT IIRC?
 
How many miles? It could be many things. Maybe it is inefficient precats (and time for mileliminators.)

From TSB,

CATALYST EFFICIENCY MONITOR

P0420 - Catalyst System Efficiency Below Threshold (Bank 1)Indicates Bank 1 catalyst system efficiency is below the acceptable threshold.

· Malfunctioning ECT/CHT
· High fuel pressure
· Damaged exhaust manifold
· Cylinder misfiring
· HO2S wiring concerns (shorted or chafed, bent pins, etc.)
· Damaged exhaust system pipe
· Damaged muffler/tailpipe assembly
· Retarded spark timing

Damaged Catalytic Converter:
· Use of leaded fuel
· Oil contamination/consumption
· Silicone contamination (sealants/cleaners)

P0430 - Catalyst System Efficiency Below Threshold (Bank 2)Same as DTC P0420, but opposite bank.See Possible Causes for DTC P0420
 
105k miles. 98 csvt. here's what i have done to it lately.
new plugs, wires
1 upstream 02 sensor changed at 75k miles
1 upstream 02 sensor changed at about 90k miles
about 2 weeks ago, i took out my plugs and gaped them all at .054 (they were all at .050 or so, but were not equally gapped)...
i have a k&N short ram (no heat shield)
superchip

i am thinking of putting on headers on, which will eliminate the precats, and i will be using mil eliminators, however, if the problem is not the cats i have now, i would like to fix it, even though my cel will not be coming on after i do the eliminators...

what else could it be? i reset the ecu and will see if it will come on again? could be bad gas?
 
8000RPM said:
105k miles. ....
what else could it be? i reset the ecu and will see if it will come on again? could be bad gas?
Click to expand...
Could be many things. As edited earlier, check those items in the TSB. Yes, it is possible for bad gas to cause misfiring (once or twice) and then the codes to trip. Don't feed it anymore beans. :laugh: .

No, seriously, if you did not put in 91 octane, it may have caused it. God only knows what the "mom and pop" stores have in their underground storage tanks in DC.
 
i always put octane 93/94. what is the deal with the IAT? what is it, intake air temp?? a sensor? can i clean it? and what does iirc stands for, i see that all the time...
"check those items in the TSB" -- in where?? those abbreviations are getting me lost :) lol
 
8000RPM said:
i always put octane 93/94. what is the deal with the IAT? what is it, intake air temp?? a sensor? can i clean it? and what does iirc stands for, i see that all the time...
"check those items in the TSB" -- in where?? those abbreviations are getting me lost :) lol
Click to expand...

Yes, IAT is Intake Air Temperature sensor. You can test it. Go to the Autozone website and find out how to test it. I'm not sure if you can clean it. IIRC, If I remember correctly. TSB, technical service bulletin. A how to by the car manufacturers. Look in my edited first reply in this thread.

Edit. Autozone link for IAT testing
http://www.autozone.com/servlet/UiB..._us/0900823d/80/1b/ca/f8/0900823d801bcaf8.jsp

Click Figure 5 for IAT specifications (same as ECT specs)
http://www.autozone.com/servlet/UiB..._us/0900823d/80/1b/ca/ba/0900823d801bcaba.jsp
 
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ok i saw your edited reply. well here's what i think, and stop me if i am wrong:
all these (below) are true only if i get one of these codes. in other words, if any of these happens, i might get the code for that specific bank. (ex a misfire in cylinder 1 will trigger the code in bank 1, but not 2...HO2S wire problem will give the code for that spexific HO2S...)
· Damaged exhaust manifold
· Cylinder misfiring
· HO2S wiring concerns (shorted or chafed, bent pins, etc.)
· Damaged exhaust system pipe
· Damaged muffler/tailpipe assembly
tailpipes are fine, but are after the sensor, so i don't see how they will affect it, unless someone put potatos in both of my tips:) lol. i have almost no restriction there due to the only 1 existing resonator after the main cat.

so by ueliminating the above, that brings me to the idea that
Malfunctioning ECT/CHT
· High fuel pressure
· Retarded spark timing
are the once that can possibly cause both sensors to trigger a code at the same time...or not?

well let me ask you. 1) if there was a misfire, shouldn't i also get a misfire code? 2) what's the deal with high fuel pressure? 3) what's the ECT/CHT? :))
abbreviations again....tststs
i will check how to test the IAT...thanks for that tip and links

BigJim - i cleared them and will drive it like you are saying. hope they wont come back!!
 
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Acronymns in this TSB,
http://www.v8sho.com/SHO/TSB0197HO2SServiceTips.htm

What?!!! You live in Washington DC and you are not into acronymns?!!! :laugh:

"Malfunctioning ECT/CHT
· High fuel pressure
· Retarded spark timing
are the once that can possibly cause both sensors to trigger a code at the same time...or not?"

Correct and most probably.

"if there was a misfire, shouldn't i also get a misfire code?"

Sometimes, the code has not been triggered yet. It might come on for it later or it might have gone to a limp mode and the PCM disregards new codes after that.

"what's the deal with high fuel pressure?"

Fuel pump, fuel sensor, or fuel injectors.
 
interesting. I have these same two codes and a terrrrible misfire across the whole RPM range.

I have my lower o2s turned off in my tune. I have retained my EGR, it is the newer 3L valve, but my DPFE is 100k miles old. Perhaps I should change it?!

Could this cause the misfire and fouling of my plugs?! Sorry to hijack, but I see no point in starting a new thread over the similar issues.
 
Last edited:
Tony2005 said:
"my DPFE is 100k miles old. Perhaps I should change it?!"

While 100k miles is a long time (I'm not sure what the design life of a DPFE is) and you can't go wrong with changing it, it might be better to test it first before shelling out $70 or so for a new one.
http://www.autozone.com/servlet/UiB..._us/0900823d/80/1b/ca/1e/0900823d801bca1e.jsp

Edit. I think you would get a DPFE code if it is malfunctioning.
http://www.fordscorpio.co.uk/egrmonitor.htm
Click to expand...


I just checked the DPFE voltage and I am getting NOTHING! I checked it via my datalogging software.

And I was throwing code p0402 which is the DPFE code so I am going to replace this thing ASAP!

Part # F7UE-9J460-AA


 
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wait, so you got the same codes and your downstream O2 sensors are disabled??? then how does the car know that the cats are bad, if there's no sensor to measure the exhaust gasses after the pre cats??? so could a misfire of 1 cyl for example cause both codes?
let me know if you fix your problem...however i doubt it if it is you DPFE. I've changed mine twice and is always been assosiated with different codes...
 
8000RPM said:
wait, so you got the same codes and your downstream O2 sensors are disabled??? then how does the car know that the cats are bad, if there's no sensor to measure the exhaust gasses after the pre cats??? so could a misfire of 1 cyl for example cause both codes?
let me know if you fix your problem...however i doubt it if it is you DPFE. I've changed mine twice and is always been assosiated with different codes...
Click to expand...

I am dyslexic and my code was 402 not 420...ooops :shrug:
 
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