P0422 and P0128 code help ? - Kia Forum
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#1 (permalink) Old 03-30-2009, 11:31 PM
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Exclamation P0422 and P0128 code help ?

I just got my new OBD2 scanner with "Live Data Stream" and I am still getting the same codes P0422 (pre-cat) and P0128 (too cold) but after monitoring the O2 sensors and temperature I need some help figuring out these 2 codes.

P0128: The engine temp varied from 183F to 192F and averaged around 185F which to me seems well within spec for a 185 degree thermostat, but the P0128 code keeps popping up and it's getting warmer here like in the 50's so it's not the extreme cold, any ideas ? Gauge shows slightly below middle of the range.

P0422:
While monitoring the Bank 1 O2 sensors I noted B1S1 going as low as .080v and high as .700v and B1S2 never going below .100v and as high as .800v, but under acceleration the B1S1 sensor before the pre-cat would show a rich condition like .700v while B1S2 after the pre-cat was showing a lean condition like .100v. To be honest I didn't see much wrong with the readings as they are cycling between .1v to .8v, any ideas guys ? How sensitive is the Kia computer to setting this code ?

Thanks guys.....................Slydog
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#2 (permalink) Old 03-31-2009, 07:36 PM
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sensor 2 shouldn't be fluctuating that much. it should stay pretty close to a constant voltage once the cat is up to temp. if it fluctuates that much when the cat is hot like that, it's gonna throw the P0422. if it was a cat though, it should throw a P0420 Catalyst below efficiency code. can't remember what the P0422 code is and KGIS won't let me look it up since my internet exploder on my computer won't work (this is why i like firefox). is that an o2 sensor code?

as for the P0128, is the coolant level good? not too much coolant in the mix? has the thermostat ever been changed?

what's your freeze frame data on the codes say?

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Last edited by kiaracer; 03-31-2009 at 07:40 PM. Reason: additional questions
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#3 (permalink) Old 04-01-2009, 05:08 AM
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Kiaracer,

Thanks for the information, I went out tonight and went for another drive with the scanner hooked up and monitoring the data stream and here's what I got.

Outside temp: 35 F


Engine started and idle readings at 1k rpm......


B1S1 =.310v

SHRTFTB1S1 % = 0%

B1S2 =.475v

After car warmed up to 185 F........

B1S1 = .110v to .700v

B1S2 = .200v to .700v

TP % = 10.6%

Under hard acceleration at 185 F..........

B1S1 = .550v

B1S2 = .110v

Temp varied from 183 F to 195 F but averaged around 189 F

Here is the freeze frame data for P0422 (Main catalyst below threshold)

*Fuel System = CL

*Load PCT % = 5.9%

*ETC (F) =185 F

*SHRTFT1 % = -1.6%

*LONFT1 % = 6.3

*RPM = 2080

*VSS (mph) = 43 mph

I also noted something odd that both O2 sensors would go to 0.00 volts when I would let off the gas pedal while driving around 50 mph then when I hit the pedal again it would start cycling again. TP % was 10.6% when I let off the gas.

So the car warmed up to 185 F then cycled between 183 F to 195 F while it is 35 F outside. The O2 sensors varied from .200v to .700v even when the car was at 189 F and to be honest they seemed all over the place.

Thanks for your help Kiaracer, I am going out of town on a couple thousand mile trip in two weeks and want to make sure the catalytic converter is not going out and get this thing fixed so the MPG will be okay.

Slydog
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#4 (permalink) Old 04-02-2009, 02:59 PM
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sensor 1 is gonna be everywhere. that's normal because it's constantly adjusting the fuel trim but sensor 2 monitors the cat. sensor 2 should be a constant voltage. if sensor 2's readings follow sensor 1's readings, the cat is done. the only cat that is monitored is the pre-cat or warm-up cat on the manifold. the main cat isn't monitored but if the pre-cat is breaking apart, all those pieces of ceramic are gonna make their way downstream so you may want to pull both cats off and check them. if there's any material from the pre-cat in the main cat, you're gonna be stuck buying 2 cats which is gonna be pricey.

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#5 (permalink) Old 04-02-2009, 10:58 PM
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Just a theoretical question (because I know for a fact that no one ever would do something so shady as to attempt to bypass a pollution control device). If a guy were to pull off the catalytic converters, bash the insides out with a pry bar (or other such dainty apparatus), bolt them back onto the car, and replaced the downstream O2 sensor with a power supply that fed the computer a constant .5V signal, would the computer tune the fuel pulse using the first O2 sensor and think that the catalytic converters were intact and doing a lovely job?

Just a point of curiosity.
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#6 (permalink) Old 04-03-2009, 07:03 AM
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itwasthedog,

You think a lot like I do, I have wondered the same thing as I don't care much about it being perfectly legal I just want the MIL light off and to get good mileage. It would not be that hard to design a circuit that you could vary the O2 sensor voltage to the computer to trick it to think it has the proper .5v which would be right in the middle of lean and rich,nice sweet spot. Heck take it one step further and mount the circuit and a variable potentiometer in the car with you to vary the air fuel ratio on the go for best driveability and MPG !

To be honest I plan on pulling the pre-cat and gutting it if it is coming apart then vac out the pipe to the main cat and make sure it is not clogged and just clean the O2 sensors so I can make the trip wthout any worries of the cat collapsing while on a long trip.

Then if I still set a code decide on getting another pre-cat and new O2 sensors or just relocate the downstream O2 sensor after the main cat or trick the computer to think it's getting .5v like you say to make it happy and just leave the pre-cat gutted and free flowing !

Kiaracer, thanks for the help, I plan dropping the cats next week and checking them and going from there. Do you think if I gut the pre-cat and install new O2 sensors that it will still trip the MIL light ? I wasn't sure if a clogged pre-cat could be causing my downstream O2 sensors reading to be so eratic even when warmed up to operating temp.

I also did some more research on the P0128 (too cold/stuck thermostat) code and it appears some Kia's around 2001 had the wrong temp thermostats or the wrong programming for the computer which would cause it to set the code, apparently the sweet spot thermostat to keep the MIL light off for this code is a 192 F thermostat and not a 185 F.

It doesn't seem like that much and I have never owned a car that set a MIL light for running too cold but alas my Kia keeps setting the code although the car runs in the 185F to 190F range. So I am going to get a 192F thermostat and swap it out with a new gasket and see if that helps the P0128 code.

Will update when I know more................thanks guys.................Slydog
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#7 (permalink) Old 04-03-2009, 07:53 AM
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Slydog -

A few months back, I was thinking seriously of getting rid of the computer on my little POS 97 kia, and Kiaracer clued me into the neatest thing since sliced bread - www dot megamanual dot com. It's the manual (for free! Can you believe it?) for an engine management system computer that a couple of weapons design engineers came up with (if I read the story right).

This computer uses just a few sensors - intake temperature, intake pressure, throttle position sensor, engine temp, O2 (just one that sniffs the exhaust coming out of the motor to fine tune the fuel - no sensor to test the catastrophic converter), and a crank or cam trigger (something that will sense RPM and engine position). That's it for mandatory sensors, and the O2, temperature and pressure sensors are GM stuff that is common and CHEAP! You can program the thing to use just about any sensor too! You can adjust the pulse of your injectors (be they high or low impedance) so it will work any injector you can think of. It has a trigger output for your ignition too! The kit to build your own computer is about $280 - WAY cheaper than any after market computer I've seen.

The only drawback I've seen with it so far is the massive amount of reading a guy has to do. I printed quite a bit of the megamanual off the web, and I have a 4" three ring binder with about 400 pages of info I'm about 70% done reading. It takes a lot of time and Anicin, but the TV sucks most of the time anyhow.

My big plan for my POS Kia is to put one of these computers on it and learn how to use the computer. I think the car will have far more value for me as an educational tool than it has as a mode of transportation.

Big thanks to Kiaracer for providing me with a new hobby (or obsession, as my wife calls it) . It's a real process bringing my level of knowledge out of the stone ages, but I'll try to catch up!
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#8 (permalink) Old 04-04-2009, 07:37 PM
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a clogged pre-cat won't set any codes, you'll just get slow acceleration and bogging down of the engine. with the ecu throwing a catalyst below efficiency code, it's telling you that there is not enough catalyst material in the converter to control the vehicle's emissions properly which basically means that the cat is breaking apart. if you were to break out all of the remaining material in the cat and put new sensors in it would still set a catalyst code because there wouldn't be any catalyst to monitor. sensor 1 and sensor 2 would be reading the same readings. the .5 volt power supply idea is kind of interesting but not sure if it would work or not. sensor 2 on start up usually reads several different voltages before the cat warms up. when the cat warms up the voltage levels out to somewhere around the .5 volts. i don't know what the ecu would think if there was a constant .5 volts from sensor 2 when the engine is cold. a simpler way to do it would be to get an o2 sensor extender like or similar to THIS and screw it into sensor 2's spot and then screw sensor 2 into the extender. this should keep you from getting a CEL with a gutted out cat converter.

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#9 (permalink) Old 04-04-2009, 10:53 PM
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Is'nt the 0422 a code for the precat and the 0420 code for the 2nd cat?
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#10 (permalink) Old 04-05-2009, 04:02 AM
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Kiazilla,

My book reads p0420 as (cataslyst system effiency below threshold) and p0422 reads (main catalyst efficiency below threshold).

Kiaracer,

Thanks for the information, I too liked the idea of the .5v supply but was concerned about what the ECU would see if it doesn't cycle like it should, so I put my electronic engineering background to work and built an O2 simulator with variable voltage for lean and rich mixture.

The way I understand the ECU looks at the O2 sensor and if it see's .8v for an extended perion of time it will "lean" up the fuel mixture to compensate and if it see's .1v it will "richen" the fuel mixture.

The circuit I built will turn on with the key and accepts 12-15 volts DC power and oscillates a waveform every 3 seconds from 0v to .8v or you can set it full rich .9v or full lean 0v and the computer will compensate and either richen the fuel mixture or lean it out based on the O2 simulator settings. It can also be set anywhere in between and more toward lean side it cycles faster from 0v to .8v or more on the rich side it will stay at .8v longer then cycle off to 0v.

Kia racer do you know what voltages the Kia Sephia computer is looking for from the downstream O2 sensor on startup when cold and when fully warmed up? From my research it seems even when warmed up it still cycles from 0v to .8v on a stock OBD2 system but stays on longer thus when using the scanner to read voltages appears to be more stable. What does your Kia O2 readings measure when monitoring the "Live data stream" for the sensors on cold versus warmed up?

I will not get a chance to test it on the car until sometime next week, but bench testing looks promising I am just wondering what voltage would be best and if faster switching is better for the Kia ECU as it seems the standard is around every 3 seconds per cycle.

Thanks guys for all the help and information, I am looking forward to trying this out and seeing how it works after the pre-cat has been gutted....................Slydog
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