These codes always haunt me. I've cleaned my throttle and maf and it didn't help. I did find a vacuum leak before on the pcv system and that helped for like a week. Yesterday I also noticed the black clip on the tps connector was broken and it popped off while driving, I found a temporary fix. I was rushing this morning but my LTFT is at -15, idling. I dont get why both sides are running rich unless I somehow have 2 bad injectors which I dont see as very likely. If that connector was the problem with it not making a good connection and me "fixing it" could I just need to disconnect the battery to erase the stored fuel trims and try again. Thank you in advance.
Persistent p0172 and p0175
- Thread starter MBS1994
- Start date
it costs nothing to try... 
the sensor is the "reading" to help the system determine how much "stuff" is being taken in so if those values are / were wrong, it does take some time for the system to correct.
the sensor is the "reading" to help the system determine how much "stuff" is being taken in so if those values are / were wrong, it does take some time for the system to correct.I dont get to drive it often so do you think my best bet would be unplug the battery to erase stored datait costs nothing to try...
Last edited:
Mooseman
Moderator
There is a "relearn" of basic idle... I think it goes something like... let it idle for two minutes, turn it off for 1 minute, turn it back on and check idle again. IF it hasn't returned to "normal", you can try repeat the process but if it doesn't return to normal, then you also have to do moderate drive runs with some stop and go to get the system to relearn. Assuming the attached page is accurate.
Last edited:
Mooseman
Moderator
Mooseman
Moderator
Mike534x
Member
- Apr 9, 2012
- 935
Definitely follow the instructions, don't make the same mistake I did. When I first cleaned my throttle body, I didn't do the relearn procedures so I ended up with a high idle CEL code because it was idling at 1K.
I came across a post on the TB SS forum, that involves letting the truck running (without touching the gas pedal) for 3 mins, off for 1, followed by running again for 3 mins, and off for a minute before starting it up and taking it for a test drive. Mine wouldn't go through with this attempt, but I found a TSB that involved what @budwich mentioned that required pulling the negative cable, and letting the PCM reset for about an hour followed by an hour of mixed highway/rush hour driving that allowed varied accelerations/de-accelerations before it finally accepted the relearn.
This time, when I replaced my throttle body over the weekend I pulled the PCM fuses and letting it sit for about a half hour. Then I ran it through the start up/shut down cycle during my first attempt and it took the relearn without a problem. Mine was replaced due to erratic idle, and a lean condition that wasn't setting a CEL. No idea why GM made everything about the V8 a pain to work with.
I came across a post on the TB SS forum, that involves letting the truck running (without touching the gas pedal) for 3 mins, off for 1, followed by running again for 3 mins, and off for a minute before starting it up and taking it for a test drive. Mine wouldn't go through with this attempt, but I found a TSB that involved what @budwich mentioned that required pulling the negative cable, and letting the PCM reset for about an hour followed by an hour of mixed highway/rush hour driving that allowed varied accelerations/de-accelerations before it finally accepted the relearn.
This time, when I replaced my throttle body over the weekend I pulled the PCM fuses and letting it sit for about a half hour. Then I ran it through the start up/shut down cycle during my first attempt and it took the relearn without a problem. Mine was replaced due to erratic idle, and a lean condition that wasn't setting a CEL. No idea why GM made everything about the V8 a pain to work with.
Last edited:
So I was -15.69 ltft constant it would move, stft was obviously all over the place but -6 to -3. Once I unplugged that hose on the intake the stft instant jumped into the positives barely ever dipping into the negative. I dont even know what that hose it but it seems like a problem no?
Attachments
Mooseman
Moderator
All you did was introduce a vacuum leak which counterbalanced the rich condition. Not a fix.
Along with the throttle relearn, you should also clean the MAF and MAP.
Along with the throttle relearn, you should also clean the MAF and MAP.
Okay sorry I know it's a lot of pictures and I dont know what most even are trying to tell me to be honest. Only things I noticed is those big spikes and dips occur at the same time my motor will sputter up or down, my o2 voltage between the two aren't even close to the same, and I failed my o2 sensor and my evap and the evap was over -7000 which I dont know what normal should be. If you make it through all the photos you are a legend.
Attachments
-
Screenshot_20200806-173852.jpg -
Screenshot_20200806-173903.jpg -
Screenshot_20200806-174136.jpg -
Screenshot_20200806-174059.jpg -
Screenshot_20200806-173110.jpg -
Screenshot_20200806-174213.jpg -
Screenshot_20200806-173113.jpg -
Screenshot_20200806-174521.jpg -
Screenshot_20200806-174527.jpg -
Screenshot_20200806-173352.jpg -
Screenshot_20200806-173547.jpg -
Screenshot_20200806-174539.jpg -
Screenshot_20200806-173601.jpg -
Screenshot_20200806-174705.jpg -
Screenshot_20200806-174714.jpg -
Screenshot_20200806-173605.jpg -
Screenshot_20200806-173658.jpg -
Screenshot_20200806-173743.jpg
wow lots of nice graphs... One thing, you should check your misfire counts. They may be pegging but not enough to cause a check light, either solid or flashing.
My guess right now is that you have a MAP problem. Relatively cheap to replace because of the idle level.
One thing, you should check your misfire counts. They may be pegging but not enough to cause a check light, either solid or flashing.My guess right now is that you have a MAP problem. Relatively cheap to replace because of the idle level.
Not sure my app and little scanner can check misfore count unfortunately. And thank you I was worried maybe it was overkillwow lots of nice graphs...
My guess right now is that you have a MAP problem. Relatively cheap to replace because of the idle level.
That Evap pressure looks silly high, like something is not venting at all. Clogged canister maybe? And it's that high with only a 14% purge cycle?? When you measure evap pressure with a Tech 2 it is measured in inches of water column. I've seen my Yukon as high as 10.something and it has set a DTC code for that now and then. Convert your pascals of -7743 to inches of water column and you're looking at roughly 31 inches!!
Here's a test. Not certain what it tells us but with my Yukon I have high LTFT, like 10 or so. If I loosen the gas cap and drive and watch those fuel trims they drop right down to near zero. Tighten the cap and they go right back up.
I think I'll do a purge and seal test tomorrow on the Yukon to see how high that tank vacuum can go.
What about the bad o2 sensor on bank 2? I also had the warning message about loose gas cap erased. Also the purge canister has been replaced twice
Last edited:
another test you can try is disconnecting the MAF and then watching the response on the trims. They should stay relatively unchanged at "normal idle". Of course, you may get a check light with a appropriate code but the engine should run somewhat "normal".
I'll try that and I also saw the gas cap tactic too
A cheap elm327 and the app is literally called car scanner.
One thing I noticed is I dont have rear o2s in the exhaust and they were tuned out but they both still read a voltage and one reads fuel trim, unless it's making a guess
for $5, you can buy the torque app for android that has the available PIDs for things like misfires that you can readily look at with your existing elm327 (not really special about it... although some "clones" may have problems... but it is likely they would have had problems with your car scanner app also).
Aha!! I have Car Scanner also, but just never really looked at it much. Just now I took a look and it appears to be able to import 'custom sensor' information from a file. I might take a look at that and see if it can import PIDs that could be useful to your situation like fuel trim cell and fuel trim index.
Your O2s2 has been physically removed and the PCM reflashed to disable the checking of catalyst efficiency?? Do you know what else may have been 'tuned'? And might this 'tuning' be affecting fuel/air mixtures?
So... confirmation... Car Scanner can indeed import PIDs from a file and display the data. I would need to setup the file as it doesn't use the very same format as Torque or OBD Fusion but that's simple enough. Car Scanner looks to have a number of nice useful graohs and live data monitors that Torque lacks. Here as an example are the injector timings and a shot of custom sensors (pids) imported.
But if I do the custom files to calm it down could that mess with my tune or mask what could be a underlying problem. Pcmofnc did the delete and as far as the tune I just told them I have LTs, 3 inch y pipe, hi flow cats, and to delete the rear o2s. Not sure what all the did to compensate for everything
I'll have to look at it and see. I'm curious though because on the emission side of the app I failed the o2 sensor, b2s1 seems dead and the evap is way overboard, so if those could be my issue. I have a vacuum tester so I might have to try and find info on what everything should be sitting at.
I think I saw that data was for the 'current drive cycle'. That might mean the failure doesn't apply across the board.
The $5 will at least confirm some of the info... just in case... some apps have been known to have "calculation issues". IF the o2 sensor (bank2) is continuing to show similar results all the time at idle (compared to bank 1), that would be looking at a replacement maybe. Now, that you indicate that you have had some mod's done and "tuned", that might be a different story in total. Of course, you don't have the "pre-tuned charts"... I am still thinking you have a MAP issue.
IF the o2 sensor (bank2) is continuing to show similar results all the time at idle (compared to bank 1), that would be looking at a replacement maybe. Now, that you indicate that you have had some mod's done and "tuned", that might be a different story in total. Of course, you don't have the "pre-tuned charts"... I am still thinking you have a MAP issue.To be clear... Nothing you do in a smartphone app like Car Scanner or Torque is going to affect your tune.
Oh I thought since that failed and it showed a constant of I believe .44v that maybe the sensor isn't working. Like I said all this electrical and readings is new to me, I'm better at tearing out and replacing. And for your second post, what would the custom files on the app do then? Sorry I am VERY noobish on this.
I was wondering about the tune being the issue but pcmofnc seems so beloved that I was thinking more my car having 215k on it than them. With the o2 I know the wires are very tight because I never but the extensions in with the long tubes so I'm hoping that it's a bad connection, driver side has a lot more slack and is functioning properly. I cleaned my map sensor last night and there was no change either so maybe a replacement. It's terrible timing because I just spent money on a shift kit and other parts so now another expensive won't sit well with the wife lolThe $5 will at least confirm some of the info... just in case... some apps have been known to have "calculation issues".
The 'custom file' I spoke of just gives the Car Scanner app the information it would need to ask for some additional parameters from the engine. When they build these apps they can only put in the parameter information they know about and those standard pids (parameter IDs) that are required by emmisions controls legislation. That and there is a ton of different cars out there with manufacturer specific information that is proprietary. As enthusiasts pick away at these vehicle they discover more parameters and how to interpret the data and it is that information that is in this 'custom file' that I would create. In reality it is nothing more than a text file in .csv format containing the details of PIDs one wants to add to the app.
Hooe that makes some sense of it.
it is quite likely that you have a connection issue as opposed to a bad sensor (assuming they are relatively new). Of course, this can be checked by doing a swap if you don't mind dealing with getting them out. Further, a bad sensor will have significant impact on the fueling ratios as I believe the system does some "averaging" to a certain degree to arrive at a result.
I don't see a graph of O2S1 Bank 2. I see Bank 1 twice, but no bank 2. In the details, not a graph, I do see 2 readings for O2S1 bank 2 and they idicate the sensor is working as one voltage is .04 and the other is .76 or the like. This would indicate that sensor is functional at least in some fashion.
The .44 you saw is O2S2 Bank 1. When the catalytics are working the upstream sensors, O2S1 bank 1 & O2S1 bank 2 should vary up and down, up and down. The O2S2 values should be steady, ideally above .6 I think.
When first started and a cold engine the O2S2 sensors should also fluctuate like the O2S1 sensors do, until the catalytics get hot enough to ignite and start burning off the pollutants. At that time the downstream sensors should become steady.
I thought of swapping but with the long tubes they are in a terrible position. They are only a few months old and I have only driven the car maybe 1k or less in the last year since it's mostly a fun car not the primary.
The readings on the upstream as far as fuel trim goes were very similar and would dip and rise at the same time so I just used one.i thought the .44 was the b1s2 in the picture of the voltage wave. There definitely shouldn't be any o2 readings in the rear that's why I was confused on the information list unless the car is making educated guesses.
Ahhh. As long as the O2 sensors are directly in the exhaust stream. I have heard of downstream O2 sensors being offset out of the exhaust stream in a attempt to fool the system into thinking that cats are workimg OK, or something like that.
I just verified that Car Scanner is using the standard mode pids 14 & 15 to get their O2S readings. I think these are legislated diagnostics but I don't know what is possible as far as a tune modifying such things. Only your tuner would know if anything has been done to fudge these readings. On my 4.2 Trailblazer there is another set of PIDs using the extended mode $22 that also display these readings. I just now compared the two and while they are very similar they are not identical it would seem.
is the chart of the o2 s2 b1 always showing the same single "wave" pattern during idle? Or is this just one time event?
