2 questions about logs

[mike96]

i have been looking at some other peoples logs to see if i can find some info on o2 sensors and the cat.

first question. what program are people using to view DSMlink logs? i dont have dsmlink.

and second question, i am looking to see if anyone has a log i can view. car needs to have cat log needs to have both o2 sensors and i would perfer if the log was for regular driving and not a WOT pull.

 

[snowborder714]

Go here and click on "Full install, v2.5.2.27" to download the DSMlink program. You can then use this to view any DSMlink log posted on here.

Is there a reason you want logs of the two sensors? What is the problem you're trying to solve?

 

[mike96]

i keep getting a P0170. i have done a lot of searching and have tried fixing about everything i can find that might cause it. i have no exhaust leaks, 2 new O2 sensors, fuel pressure is good, no intake leaks. the only thing that has been changed is i am running an evo3 turbo at stock pressure and there is no cat on my car. i read some where, not sure if it was here or on one of the DSM ECU yahoo groups, that the ecu uses the second O2 sensor to fine tune the fuel trim. i was thinking that if that's true than ma-by the ecu is looking for a difference in the two sensors and is adjusting the fuel to try to fix a problem that doesn't exists. like ma-by the ecu thinks there is too much fuel going through the system and the cat cant burn it all off. so i was thinking that i might toss in a resistor to drop the signal on the one sensor to get the difference in reading the ecu might be looking for. i just need to know what the average signal difference is on a car with a cat.

 

[1992awdlaser]

The front o2 sensor is the one that controls the fuel trims. This is why the rear o2 sensor can be eliminated to be able to run a wideband in that location. The rear o2 sensor just checks to make sure the cat is doing its job.

 

[Nito15]

What 1992AWDLaser said, the exhaust having no cat is causing your secondary O2 reading to be off and it is highly likely why you get that code.

 

[mike96]

i remember reading it somewhere so i thought it was worth looking into... i think i am about at the point where i think the ecu might be bad............

 

[mike96]

another question then with no cat why dont i get a code for that?

 

[kenamond]

If I recall that code correctly, it means that you're running too rich or too lean, and it's so bad that the ECU cannot compensate for it via fuel trims. I forget the +/- limits for trims, but if the ECU has to add/remove too much fuel based on the *front* O2 signal, and it's so bad that it hits the limits hard-coded into the ECU, it throws the code.

If you're running lean, it could be bad fuel pressure, clogged injectors, etc. If it's running rich, it could be high fuel pressure (aftermarket fuel pump and stock (overrun) FPR can do this). I'd invest in a logger and find out if it's too rich or too lean and go from there.

All of this is based on closed-loop mode of the ECU. So if during cruise, you seem to have bad MPG or see black smoke out the tailpipe, or the exhaust smells like fuel, then I'd say you're running rich. If it's not any of those, maybe you can read your plugs after you've been cruising to see if they're white-crusted or otherwise lean-looking.

If it's not a front O2 sensor, my guess is that you've got another fuel problem (too much or too little) that you should look into. If you count all of those out, it could be a bad ECU I guess, but I don't know enough about bad-ECU-symptoms.

Have you done a boost leak test lately?

 

[mike96]

ok i am tring to log my car came with a palm, i use it more to check and clear codes. than anything else. i cant get the tunerstein player to install on my pc, i have another program that i can use to log with but i donot know if i can transfer it to my pc, its called OBDgauge.

 

[mike96]

boost leak check about a month ago and everything checks out good. i have a logger running now and i can log i just cant transfer the logs to my PC. every time i try it just starts running really ssssssssssssllllllllllooooooooooowwwwwwwwwwwww. and then just resets back to the player screen as if you had just started the program. so i am going to look into getting either my other laptop running and use that or what.

i can tell you that when i did log on the freeway today, at a pretty steady cruse the o2 sensor jumped around like the himalayas.......

 

[kenamond]

When in closed-loop mode (like when cruising), the ECU tries to keep the AFR at stoich by getting the O2 sensor to swing back and forth around 0.5v. If that's what it's doing, that's normal. But I don't know what the O2v will do if you've pegged the trims and thrown that code.

 

[mike96]

looking through the log the voltage is jumping from the extreme low .17 and and the highest .81 the average low was around .27 and the average hi around .75. i will see what i can get you for a snap shot.

 

[1992awdlaser]

looking through the log the voltage is jumping from the extreme low .17 and and the highest .81 the average low was around .27 and the average hi around .75. i will see what i can get you for a snap shot.

That sounds like perfectly normal o2 sensor activity during closed loop operation.

 

[snowborder714]

I agree with Pat. That voltage range is normal for idle or cruise.

 

[mike96]

does it really verry that much???

is there anything else i might be missing that might cause a P0170? i think i have fixed everything else i found on the forum that might cause a problem.

 

[snowborder714]

Look at the log in this post. If you take all the lines off the graph (Ctrl + Z) and then just check the FrontO2, you'll see it fluctuate (.04 to .86) at the very beginning of the log.
http://www.dsmtuners.com/forums/log-file-advice/305136-dsmlink-log-take-look.html#post151584195