Murder Snake

Did a search on here as well as general search on the net and nothing specific to my situation. here is the deal: had the computer recall flash done, the car had the code of the bad sensor and/or cat. I replaced the cat with an OEM manifold/cat, replaced the front 02 sensor and all was good for about 1 week, now, it is throwing the code I listed. the connection was fine when plugged in...no ripped or torn wires. I don't hear any leaks from the exhaust and the car runs fine. thoughts????

RT78

Go to advance auto and rent a scan tool, hook it up and bring up the data stream list, you'll see 2 entries for O2, it'll be O21 and O22, O21 is your upstream sensor in the manifold, the voltage should fluctuate rapidly from a negative to a positive number, that's how you know the sensor is working, if you get no voltage signal from it, it's a dead sensor. Could just be a faulty sensor, but I'm not to good with testing electrical stuff on cars so somebody else will have to tell you about that aspect.

Murder Snake

Thanx for the info! I just got a scan tool of my own and had done the trouble codes. so tried the data stream. the car was off, but here is what I got:

now two codes:

P0171, lean condition, bank 1

P 0134, as before

did what it allowed: an oxygen test as it did not have 021 you spoke of, at least with the car not running.

it gave me three tests:

TID 1: values: 0.52V
TID2: values: 0.52V
TID70: test value: 39
minimum value: 0
maximum value: 25

don't know what that means, but that is what it told me. i was afraid to start the car and have it run while the scan tool was connected as I don't know that that would do.

Green_Bandit

iTrader: (25)

I get the no activity code every so often. Goes away on its own and never really caused a problem.

Murder Snake

do you get the 0134 code with it?

eusgen

iTrader: (5)

You can use the scanner while the car is running... that is how you need to check your o2 sensor. Where about in florida do you live?

Murder Snake

Thanx for the info. will try that. I am in the Tampa Bay area.

RT78

yeah, if it's off you'll have no signal voltage from the sensor cause it won't be monitoring the exhaust emissions

Murder Snake

ok, checked it running. I don't have an 021 and 025, there is a listing for o2s11 and o2s12. the s11 is showing a fluctuating v and the percentage fluctuates, stays mainly as a negative value. the s12 has no fluctuating v and fluctuates the percentage like the other one.

Murder Snake

searching the net, looks like s11 is the upstream and s12 is the downstream. the downstream volts don't change, so guess I will change that one too and see what happens. I can also, at some point, stick the old upstream back in since I don't know if the o2 was bad or the cat or both. seemed that from what a Mitsubishi tech told me, it was the cat. so did both, just to make sure. will probably stick the downstream one in, see what happens and go from there.

RT78

Ok, if the upstream sensor is staying at mostly a negative value it's trying to lean out the fuel mixture(reduce the amount of fuel), you're running rich, a lot of fuel being pumped into the motor. The downstream sensor should stay at a near constant value any dramatic fluctuation means that the cat isn't working as efficiently as is should, a good voltage value for the downstream 02 is around .6-.7v. If you want a REAL good explanation of how O2 sensors work a guy named scannerdanner on youtube makes vids about all kinds of stuff, the guys an auto tech teacher and records alot of his classes and posts em. But back to the sensors, with the car running rich, it's probably fouling the O2 from fuel not being burned in the motor and that's bad for your converters too, you've got to get to the bottom of why you're running rich in order to fix the sensor problems or you're gonna keep going through em.

Murder Snake

fouling both or just the upstream? I will take down some of the fluctuations when my daughter gets home from school.

I did have the computer recall done at the dealer as that had no limits on time or mileage....now I am wondering if they really did it since, I believe the reflash was due to that very problem you describe.

will have to research what the most common reason for the running rich issue is on these cars.

I really appreciate all of you help and input!!!!!!!!!!! Thank you!!!!!!!!

RT78

No problem for the help, I've been that person pulling his hair out behind car problems before, I know it's NO fun. As far as I know the downstream sensor shouldn't really get fouled from running rich, but I may be wrong. Most of the time the unburned fuel will just settle in the converters where it will either clog them or eventually get to the point that they melt internally from the high temps of burning fuel inside them. When you check downstream O2 voltage if you see a drop from lets say .6v to like .2v and back up somewhat repeatedly then I would think you have some restriction in the second converter. When you check the voltages in the datastream list, scroll down to where you'll see STFT and LTFT, tell me what those values are, that's your short term and long term fuel trim, that's another way I learned to diagnose mixture issues from scannerdanner, if you have like 30 mins of free time definitely check out his videos, they're invaluable.

Murder Snake

I watched, partially, one of his and then another guy's fuel trim video that wasn't very long. learned some, however, I have a lot to learn about all of this. in any case, took my little scan tool out and wrote down all this info:

st frm 1 % 0.0 to -0.7
st frm 2 % 7.8 & 8.5

IAT 46 or 47

MAF 9m/sec 2.21, but fluctuated 2.11 to 2.22

ABSLT TPS % 0.0

O2S11 .000 - .540V %: 2.3 to -.7 and one time to -5.4
O2S12 0.840 %: 0.0 TO -.07

IGN ADV 6-10


then I switched out the upstream o2 sensor to the old one that was in with the alleged bad cat. cleared the codes and the values changed on both 02 sensors....still had the up to -.07, but it also went as high as 24 something at idle on the upstream when I first cranked it up.

the downstream starting reacting more and then settled at the 0.840 but the values starting changing more.

I revved it a few times to see if the cel would come back on, but so far not. with driving maybe it will, but maybe I got a bad sensor.

I checked, as best I could most of the vacuum hoses I could see, all were on and did not see any breaks. I don't like the airbox setup......clamping the filter between the two sides. doesn't seem very good in the sealing department.

again, I really appreciate you taking the time to look at this and helping to educate me. I was beginning to think maybe I need to get a tuner, if they make one, for this thing and let someone tune if for me, turn off the o2's and go straight tune.

RT78

Ok, ws the second fuel trim STFT or LTFT, if it's really STFT, you're definitely running rich, with the old O2 are you getting switching back and forth between positive and negative now?


*Correction- high STFT is actually running lean, not rich, the pcm is adding fuel to the mixture, high negative STFT is running rich, the pcm is subtracting fuel from the mixture