P0430 and rear o2 sensors, ongoing issue... ( Complicated )
12-16-2011, 10:41 PM
#1
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Join Date: Mar 2008
Location: NJ/PA
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P0430 and rear o2 sensors, ongoing issue... ( Complicated )
So I had this 0430 code for about 6 months and since my car got to ~96000 miles... I did a lot of research and eventually realized its a pretty complicated, catalyst/o2 sensor related issue with too many variables that totally required OBD2 tool...
At first I thought I had a bad spark-plug, and I replaced the stock ones with Champions that created more troubles than it solved. I also replaced the front o2 sensors, which was a PITA since its near impossible to get to the front drivers side one... That did not solve the issue. After hooking up the tool I could see that the wave forms are exactly what they are NOT supposed to be - rear o2 just mirroring the front sensors, which is BAD since converters are supposed to smooth the graph is they work correctly. I check my friends '10 V6 Stang and my '96 Corolla with 300 000 miles, both vehicles have a smooth line for the rear sensors. Somewhere on YouTube I saw that old o2 sensors sometimes do respond to rich mixture but fail to stay in that state going to lean contrary to what a mixture actually is.
So I replaced the rear o2 sensors and my voltage graphs look MUCH better, but still far from perfect line I saw on my other cars... A pending 0430 code did come back at first, only to go away later, which kind of makes this even more complicated. I wish I knew someone who knew a lot about how this stuff works.
There is something I notice from driving with the o2 voltage graphs running on my laptop... Sometimes one bank produces almost ideal smooth voltage line, while another does not, while under a slightly different load/RPM another bank produces an almost ideal line while another does not. It seems this is some kind of sensor sensitivity/placement issue, or something inside the mufflers that affect the exhaust gas flow. But this seems just so difficult to troubleshoot. the OBD2 computer has a something that's called mode $06 running monitors with data on o2 sensors that supposed to stay within a correct threshold and it seems like I am barely within for the rear ones, when it goes out of range it sets a pending code and eventually a constant and a light...
BTW I am not typing this up because I expect much help on this but rather to document my issues so that when most of our cars get to 100 000K and someone looks up this info he can find some here...
At first I thought I had a bad spark-plug, and I replaced the stock ones with Champions that created more troubles than it solved. I also replaced the front o2 sensors, which was a PITA since its near impossible to get to the front drivers side one... That did not solve the issue. After hooking up the tool I could see that the wave forms are exactly what they are NOT supposed to be - rear o2 just mirroring the front sensors, which is BAD since converters are supposed to smooth the graph is they work correctly. I check my friends '10 V6 Stang and my '96 Corolla with 300 000 miles, both vehicles have a smooth line for the rear sensors. Somewhere on YouTube I saw that old o2 sensors sometimes do respond to rich mixture but fail to stay in that state going to lean contrary to what a mixture actually is.
So I replaced the rear o2 sensors and my voltage graphs look MUCH better, but still far from perfect line I saw on my other cars... A pending 0430 code did come back at first, only to go away later, which kind of makes this even more complicated. I wish I knew someone who knew a lot about how this stuff works.
There is something I notice from driving with the o2 voltage graphs running on my laptop... Sometimes one bank produces almost ideal smooth voltage line, while another does not, while under a slightly different load/RPM another bank produces an almost ideal line while another does not. It seems this is some kind of sensor sensitivity/placement issue, or something inside the mufflers that affect the exhaust gas flow. But this seems just so difficult to troubleshoot. the OBD2 computer has a something that's called mode $06 running monitors with data on o2 sensors that supposed to stay within a correct threshold and it seems like I am barely within for the rear ones, when it goes out of range it sets a pending code and eventually a constant and a light...
BTW I am not typing this up because I expect much help on this but rather to document my issues so that when most of our cars get to 100 000K and someone looks up this info he can find some here...
12-18-2011, 11:17 PM
#2
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Join Date: Mar 2008
Location: NJ/PA
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After replacing my rear o2 sensors the CEL light is gone, but I can see that Catalyst Efficiency Rate in $06 monitor mode(OBD2 software) is very close to its upper allowable limit. I also noticed that the max allowable rate on Bank 1 and Bank 2 differ for some reason, is there a reason for that?
12-19-2011, 09:51 AM
#3
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Join Date: Jun 2006
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After replacing my rear o2 sensors the CEL light is gone, but I can see that Catalyst Efficiency Rate in $06 monitor mode(OBD2 software) is very close to its upper allowable limit. I also noticed that the max allowable rate on Bank 1 and Bank 2 differ for some reason, is there a reason for that?
12-19-2011, 11:36 AM
#4
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Join Date: Feb 2008
Location: western ma
Posts: 732
This code usually means either your cats are shot or your sensors are shot. Being that you replaced the sensors and you're still showing poor efficiency readings, it's a good guess that your cats are shot. I had an '07 with a bad cat 40K miles...
12-19-2011, 11:39 AM
#5
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Join Date: Mar 2008
Location:
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Based on your mileage, codes, repairs and mode 6 data you are almost certainly looking at depleted cats. The switch rate of the sensors indicates they no longer have the ability to store oxygen. The enabling conditions for this code is the switchrate threashold which you are apparently exceeding. Really nothing but bad cats can cause this condition.
12-19-2011, 09:17 PM
#6
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Join Date: May 2007
Location: Central Texas
Posts: 2,388
Well, you've found someone who knows exactly what you're talking about.
Mode 06 monitors are various diagnostic tests that run continuously or once per driving cycle based on specific operating conditions (such as temperature, gasoline level, etc.).
The sides will not be the same, due to variances in various components in the engine and exhaust system. Typically, the front o2 signals will oscillate between rich and lean approximately 3 times every 2 seconds during part-throttle normal driving. The rear O2 sensors measure the difference in oxygen after the cat converters, and will follow the front signals, with some delay (shift) in waveform, and ideally, lower amplitude. The pcm 'counts' the number of amplitude switches between a specific time range, beyond certain thresholds. The counts accumulate over several driving cycles, and once a predefined maximum count is reached, the P0430 or P0420 code will be thrown.
The typical solution is to keep the signal voltage below the thresholds so the pcm does not count the signal variation as switching. For example, a typical rear O2 sensor would only have an amplitude of 2 volts, under normal operating conditions. But with no cat converter, the signal would be much wider and closer to the min-max 0-5v values like the front signals.
The sole purpose of the rear o2 sensors is to detect degradation in cat converter catalyst effectiveness, letting the owner know of a failing cat converter so that emissions produced is kept to a minimum.
Now, for your specific situation: what cat converters do you have? If you are running stock converters, you likely have a failing driver-side cat converter (P0430 is driver side, P0420 passenger side). The proper solution is to replace the converter.
If you have high-flow cats, it's very common to get one or both of these error codes.
The solution is to be able to attenuate the rear signal so that the amplitude is not high enough to trigger excessive switching counts. A modfication to the rear o2 signal circuit can be used for this (using a resistor and capacitor to make a simple dampening circuit), or what most people do is to move the o2 sensor out farther from the exhaust stream, using spark plug spacers to move them out while protecting a leak-proof seal.
Or, appropriate changes to the maximum threshold voltage values in the tune would alleviate the problem as well (see below).
I've spent a lot of time investigating this as well as other OBDII systems. There was a nice pdf of the '05 monitor systems online for awhile which described in detail what the monitor codes were and their expected values. If you can read OBDII mode 06 data, query pids 06 21 and 06 22, and you'll get the rear o2 catalyst values. The results include both the current counts and the max values for each.
Hope that helps.
Mode 06 monitors are various diagnostic tests that run continuously or once per driving cycle based on specific operating conditions (such as temperature, gasoline level, etc.).
The sides will not be the same, due to variances in various components in the engine and exhaust system. Typically, the front o2 signals will oscillate between rich and lean approximately 3 times every 2 seconds during part-throttle normal driving. The rear O2 sensors measure the difference in oxygen after the cat converters, and will follow the front signals, with some delay (shift) in waveform, and ideally, lower amplitude. The pcm 'counts' the number of amplitude switches between a specific time range, beyond certain thresholds. The counts accumulate over several driving cycles, and once a predefined maximum count is reached, the P0430 or P0420 code will be thrown.
The typical solution is to keep the signal voltage below the thresholds so the pcm does not count the signal variation as switching. For example, a typical rear O2 sensor would only have an amplitude of 2 volts, under normal operating conditions. But with no cat converter, the signal would be much wider and closer to the min-max 0-5v values like the front signals.
The sole purpose of the rear o2 sensors is to detect degradation in cat converter catalyst effectiveness, letting the owner know of a failing cat converter so that emissions produced is kept to a minimum.
Now, for your specific situation: what cat converters do you have? If you are running stock converters, you likely have a failing driver-side cat converter (P0430 is driver side, P0420 passenger side). The proper solution is to replace the converter.
If you have high-flow cats, it's very common to get one or both of these error codes.
The solution is to be able to attenuate the rear signal so that the amplitude is not high enough to trigger excessive switching counts. A modfication to the rear o2 signal circuit can be used for this (using a resistor and capacitor to make a simple dampening circuit), or what most people do is to move the o2 sensor out farther from the exhaust stream, using spark plug spacers to move them out while protecting a leak-proof seal.
Or, appropriate changes to the maximum threshold voltage values in the tune would alleviate the problem as well (see below).
I've spent a lot of time investigating this as well as other OBDII systems. There was a nice pdf of the '05 monitor systems online for awhile which described in detail what the monitor codes were and their expected values. If you can read OBDII mode 06 data, query pids 06 21 and 06 22, and you'll get the rear o2 catalyst values. The results include both the current counts and the max values for each.
Hope that helps.
12-19-2011, 11:04 PM
#7
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Thread Starter
Join Date: Mar 2008
Location: NJ/PA
Posts: 330
Yes, I am glad that I am not the only one who deals with this issue...
The Internet has a lot of information on those codes but no definite solutions. For
example, apparently aftermarket converters are no good and Ford OEM are crazy
expensive. (I did consider buying used ones pipes and converters from someone who
upgraded to aftermarket setup though, or possibly a junk yard solution...) Most of the
sites and documents seem to point out that cats do not wear out unless something is
going wrong with the engine. However, I had nothing wrong before the light came on,
and my driving was all highway and usually pretty set back... Now, you mention about
voltage being different on front and rear sensors, that's not what I read/see... Computer
adapts to the min max voltage which is by the way pretty much the same on front/rear
sensors, but instead reacts to the number of switches, from low to high voltage... And
yes, I do see all this info deciphered on my OBD2 laptop software. The real question is -
WHY DO LEFT/RIGHT BANK MAX THRESHOLD RATES ARE DIFFERENT? Aren't they
supposed to be the same? I am talking about max allowable cross-counts ratio, between
left and right sides? The Ford manual says it should be typically 0.6 for Y pipe systems (
two banks sharing one cat ) or 0.75 for separate banks. So we do have separate banks,
why does one bank has 0.595 and another one 0.777 threshold? Is this a programming
mistake? I wish I can contact Ford about this just to make sure it makes sense... My idle
long term fuel trims are high as well, I will probably look into replacing a fuel filter again (
replaced a couple of years/30k? miles ago ) and possibly the air filter again, and probably
check the info after using different brands of gas as well...
The Internet has a lot of information on those codes but no definite solutions. For
example, apparently aftermarket converters are no good and Ford OEM are crazy
expensive. (I did consider buying used ones pipes and converters from someone who
upgraded to aftermarket setup though, or possibly a junk yard solution...) Most of the
sites and documents seem to point out that cats do not wear out unless something is
going wrong with the engine. However, I had nothing wrong before the light came on,
and my driving was all highway and usually pretty set back... Now, you mention about
voltage being different on front and rear sensors, that's not what I read/see... Computer
adapts to the min max voltage which is by the way pretty much the same on front/rear
sensors, but instead reacts to the number of switches, from low to high voltage... And
yes, I do see all this info deciphered on my OBD2 laptop software. The real question is -
WHY DO LEFT/RIGHT BANK MAX THRESHOLD RATES ARE DIFFERENT? Aren't they
supposed to be the same? I am talking about max allowable cross-counts ratio, between
left and right sides? The Ford manual says it should be typically 0.6 for Y pipe systems (
two banks sharing one cat ) or 0.75 for separate banks. So we do have separate banks,
why does one bank has 0.595 and another one 0.777 threshold? Is this a programming
mistake? I wish I can contact Ford about this just to make sure it makes sense... My idle
long term fuel trims are high as well, I will probably look into replacing a fuel filter again (
replaced a couple of years/30k? miles ago ) and possibly the air filter again, and probably
check the info after using different brands of gas as well...
03-14-2012, 06:28 PM
#8
2nd Gear Member
Thread Starter
Join Date: Mar 2008
Location: NJ/PA
Posts: 330
Well here is a little update. Check engine light disappeared and does not come back... Just passed emissions test and got a new sticker good for 2 years... Car has 115k miles now, the light has been on for about 30k miles before I changed the plugs and all o2 sensors... It got better after I changed the rear sensors...
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