Persistent p0172 and p0175
- Thread starter MBS1994
- Start date
Yes the maf, air filter, and throttle body. No ground and no volts on green to the map now.
Scratch that nevermind
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Mike534x
Member
- Apr 9, 2012
- 1,029
If you're looking to replace the MAP sensor, the part number is AC Delco 213-4434. Little plastic tab at the top front portion of the intake holds it in. When I replaced mine, there was oil residue inside the sensor itself and the seals were worn enough that it just lifted right out. 
I already changed it with no luckIf you're looking to replace the MAP sensor, the part number is AC Delco 213-4434. Little plastic tab at the top front portion of the intake holds it in. When I replaced mine, there was oil residue inside the sensor itself and the seals were worn enough that it just lifted right out.
Mike534x
Member
- Apr 9, 2012
- 1,029
I had a code go off for the EVAP, which was the canister that attaches to the gas tank. It developed fractures/cracks where the hose leads in, causing a leak. I needed up replacing that, along with the one that sits near the throttle body. Does it show a pending code for it?
No just the p0175 and 172 so rich both banks. I've replaced the vent and and purge so under the car between the tires and the by my intake and unless I'm wrong, wouldn't be surprised at this point, the only other evap problem could be the charcoal canister.
thanks for the clarification on this as I can see I was confused. I believe the response in terms of running / not running / restart is somewhat expected (I think I recall seeing that in my MAP journey). I am going to play with my 4.2 tomorrow to refresh my memory experience... might not mean much versus the v8 but I would expect similar. The large swing is "worrisome".
Small request, can you post a picture of the two MAP that you have showing the topside / labeling?
What do you mean two MAP and also can you clarify on the "worrisome"
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That confirms my parts # lookup I think. That exactly the same as my 2005 Yukon 5.3 LM7. I just ran some tests for voltage vs vacuum along with capturing the simultaneous output of the 2 pids I have for that. 010B standard pid and the gm extended mode 22 pid 1142. The standard mode is defined as outputting the absolute pressure in kPa without needing any conversions or special equations. The extended mode pid 1142 requires an equation.
Just need to review the values and see how close my current equation comes. I developed that equation last year after doing the same test on the Trailblazer 4.2 that uses a different MAP sensor part ##.
you said you replaced it in post 119 so now you have an old one and a new one... that's what I read.
as for "worrisome", that was referring to the swing in LTFT value... I think you indicated it went from -15 or so to plus value.
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tjbaker57..."just need to review the values and see how close my current equation comes. I developed that equation last year after doing the same test on the Trailblazer 4.2 that uses a different MAP sensor part ##." are saying that the equation used in torque for 4.2 is "incorrect" or not there ... just wondering? sorry for the "side step".
Both had the same number on the top, I tossed the old one. It was torn on the tip of the orange gasket but not crazy bad. I just wanted to make sure by worrisome you weren't gonna say maybe a problem with a cyclinder.
The equation I refer to is of my own creation, used for evaluating the extended mode pid(s). For MAP these would be 1142 and 12E3.
So there are "standard PIds" that are legislated due to emissions. Among these is a pid for manifold absolute pressure. This is mode 01, pid 0B. This is where most, if not all, apps like Torque and Car Scanner get their value for MAP. The value is returned as a single hex byte when converted to decimal is the absolute pressure in kPa. Absolute pressure begins at zero as a perfect vacuum devoid of any atmosphere and rises from there.
Manufacturers are free to have their own additional pids and our GM vehicles have an extended mode (22) pid, 1142 that also returns a value from the MAP sensor. This is not returned as a preconfigured unit of pressure measurement, but just a single byte of hex that we must determine the scale and offset for and convert to some unit of measurement. Representing voltage is the easiest. A single byte of hex has a range of 0x00 to 0xFF, or decimal 0 to 255. Most sensors return a voltage ranging from 0 to 5 vdc. In equations you will see either A/255*5 or the simplified A/51 used to convert the retuned value to a voltage range of 0 to 5 vdc.
My observations of some legislated pids have suggested to me that the 'standard pids' could be somehow massaged as compared to what looks to be the raw value of the extended mode pid 221142. Still evaluating that. Additionally, I just discovered yet another entended mode pid that returns a value from the MAP, 2212E3. This recent find looks to return pretty much the same value as the 1142 pid but at a different offset. By this I mean I can take one of the extended mode pids of MAP and add or subtract a set value and get the other extended mode pid. Not sure of the intended purpose of that.
Is one the right value and the others not? They are close enough to each other to be considered the same I believe. The Tech 2 uses the extended mode pids, not the 'standard mode' pid so that might suggest the extended mode pids are desireable for diagnostics.
OK... no problem... we are aligned.... maybe a bit more now.
One thing that I did, was an "unplug" test on my 4.2 as it has been a while since I played with the sensors. Currently, the engine runs with a slight + bias for LTFT (2-3) but once warm / driven, does sit at about 0 for idle. So, I did a couple of things. First, I confirmed "normal idle". Shut down, disconnected the MAF. Started up, idle happen but LTFT started somewhat "normal" but slowly drifted toward -15/17 or so. Almost like what you have been seeing. My bad though I didn't look at the check engine light as I was looking at my tablet (running torque). I suspect that it wasn't lit.
Shut down, reconnected the MAF, restarted and the LTFT started somewhat higher negative (-10 or so) and then proceeded to head back to normal at around +1 / 2 or so. I then pulled the connector on the MAF with engine running. The engine stumbled a bit but continued to run. I did now notice the check engine light on (codes for voltages on the temp and air sensors of the MAF). The LTFT headed towards -15 / 17. With some throttle, it would go towards 0, but once released head immediately back to -15 or so. Shut down and plugged the MAF back in. Restarted. The LTFT remained significantly negative (-12-15 or so). Went for a drive of a few miles at speed. The LTFT moved towards 0 but at any time, the pedal was released headed back to significantly negative.
It didn't appear that I could get back to my previously "normal" operating LTFT's.... :-(
I then decided to reset / clear the codes with app. The LTFT remained similar (>negative). :-( I was swearing never to go on the forum again and try anything with my "test bed"...
After travelling about the same distance as initially had travelled, the LTFT returned to it previous "normal range" near 0 or a little positive. Not sure what to make of this other than perhaps, maybe your MAF is causing the system to work "negatively" because it is either giving a bad reading or some other issue which is causing the system to run "single armed" so to speak. Sorry for the long post. Not sure if it helps but maybe...You can right a book about a test and I'll read it to try to figure this thing out so no need to apologize. I am letting the car sit with no battery connection for longer this time just to try and I will do the same you did when I am off from work just to see if anything changes like yours. I'm hoping everything is fine at this point but I'm messing up the reset or not driving it long enough. I'm still concerned about the charcoal canister so I'm hoping to find more today when the car is hooked back up. Also since all this started now I'm also failing my o2 heater test which I dont think I was before.OK... no problem... we are aligned.... maybe a bit more now.
One thing that I did, was an "unplug" test on my 4.2 as it has been a while since I played with the sensors. Currently, the engine runs with a slight + bias for LTFT (2-3) but once warm / driven, does sit at about 0 for idle. So, I did a couple of things. First, I confirmed "normal idle". Shut down, disconnected the MAF. Started up, idle happen but LTFT started somewhat "normal" but slowly drifted toward -15/17 or so. Almost like what you have been seeing. My bad though I didn't look at the check engine light as I was looking at my tablet (running torque). I suspect that it wasn't lit.
Shut down, reconnected the MAF, restarted and the LTFT started somewhat higher negative (-10 or so) and then proceeded to head back to normal at around +1 / 2 or so. I then pulled the connector on the MAF with engine running. The engine stumbled a bit but continued to run. I did now notice the check engine light on (codes for voltages on the temp and air sensors of the MAF). The LTFT headed towards -15 / 17. With some throttle, it would go towards 0, but once released head immediately back to -15 or so. Shut down and plugged the MAF back in. Restarted. The LTFT remained significantly negative (-12-15 or so). Went for a drive of a few miles at speed. The LTFT moved towards 0 but at any time, the pedal was released headed back to significantly negative.
It didn't appear that I could get back to my previously "normal" operating LTFT's.... :-(
I then decided to reset / clear the codes with app. The LTFT remained similar (>negative). :-( I was swearing never to go on the forum again and try anything with my "test bed"...
Ok so no driving yet because I'm still working but on break I rehooked the battery up and still negative lt and st, it also does have a idle problem randomly where it will bog down and rise and steady. Unplugged the maf running and it died. Started it unplugged and it ran way better than when its plugged in. Unplugged though it was anyway on LT from 0-20 but mostly 10 all positive
Changed the maf and ltft at idle is a very consistent 2.34positive
. St are very negative but I just changed it to test it, no relearn. I'll relearn it tomorrow and see but I have reason to be hopeful. Oh also dont know how its connected but shifts are way firmer. 1-2 would shift pretty firmly and I thought it was just the vette servo I installed, now I dont feel it much. Performance also seems way more smooth
. St are very negative but I just changed it to test it, no relearn. I'll relearn it tomorrow and see but I have reason to be hopeful. Oh also dont know how its connected but shifts are way firmer. 1-2 would shift pretty firmly and I thought it was just the vette servo I installed, now I dont feel it much. Performance also seems way more smooth
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Good news on the MAF change and results!
Further investigation reveals this pid 12E3 seems related to MAP or maybe airflow but does not directly respond to changes in the MAP sensor. Driving tests seems to indicate it could be related to airflow. This shot shows the 12E3 somewhat following airflow perhaps. The other 2 that closely follow each other are the standard mode 010B map pid and the extended mode 221142 pid.
Further investigation reveals this pid 12E3 seems related to MAP or maybe airflow but does not directly respond to changes in the MAP sensor. Driving tests seems to indicate it could be related to airflow. This shot shows the 12E3 somewhat following airflow perhaps. The other 2 that closely follow each other are the standard mode 010B map pid and the extended mode 221142 pid.
Changed the maf and ltft at idle is a very consistent 2.34positive
good deal.... ultimately it appears that you had two problems, one a "chewy" and the other a "weak MAF".... tough troubleshoot. Hopefully, it has been resolved in terms of coding.
As for shifts, in the past and otherwise, vacuum was used for shifting along with other things like pedal position, etc ... of course, vacuum was a directed feed into the tranny itself but now can be "electrically input" via the pcm. Thus, I would expect some changes in shifts if the system has a "better grip" on its "vacuum read" withstanding other things like pedal, rpm, etc.
Mooseman
Moderator
The tranny shifting can be caused by a bad or disconnected MAF. That happened to me once where I forgot to reconnect it and it shifted to give me whiplash.
No check engine light and feels a lot better but still negative fuel trims.... 
I had positive ltft before disconnecting the battery, I drove around for quite a while, maybe just not long enough?
I had positive ltft before disconnecting the battery, I drove around for quite a while, maybe just not long enough?
I 'think' the evap monitors can take a good while to complete their tests. Like maybe days or longer. Someone help us out here??
christo829
Member
My tps connector is broken, I'd imagine that could have some impact. I had to do a make shuft quick fix since it came undone on the road so well see. But still since swapping the maf it feels a lot better but still negative trims.
christo829
Member
Ouch! Hope none of that porcelain fell in at any point. And if those are damaged, sort of makes you wonder what else might be a bit awry... Can't even tell if that's an AC Delco plug. What do the electrodes look like on it? Surprised you're not throwing some misfires, which wouldn't help your trims any, either.
All electrodes are equal to these. That's why I pulled the plugs hoping to see something before blindly replacing, I also mentioned a tick in the exhaust that isn't a leak that happens at the same time as the idle problem. I'm really hoping it's this along with I do believe my maf was bad. Oh and I think this happened when I was very rushed to finish my long tubes the day of moving cities, might have missed it or forgot because it's been a year and I dont drive it often
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well, just to close on this "promise". My "ship came in" so to speak and I got my vacuum pump.I hope to try your setup... just have to wait on a vacuum pump (from "off-shore"... could be years...
MANIFOLD ABSOLUTE PRESSURE SENSOR (MAP SENSOR)
Our main business is to develop high quality automotive diagnostic equipment, application software and hardware tools for servicing of automotive electronics.autoditex.com
Tested the MAP response of vacuum as reported by torque with a similar setup as posted here by TJ... At zero vacuum on the gage, torque reported .3 in/hg (this is basically what your vehicle will see at key on, engine no running). At ~5 in/hg on the vacuum pump gage, torque reported 4.7, at 10, torque 9.5, at 15, torque 13.9, at 20, torque 18.3. Of course, I didn't have "full control" of the vacuum as the hose fittings / "adaption" was a bit "loose".... plus there is no calibration certainty of the gage. Anyway, as can be seen, the MAP responses fairly well to the expected vacuum seen.
As part of "good news" and maybe somewhat related to this thread, I happened to have kept one of the "new replacement MAPs" that I got off of ebay in this journey. With it, my vehicle refuse to run properly as the trims were all "wrong" (ie. significantly lean / throwing code). I repeated same test with the "bad MAP". At key ON, it read 0 so perhaps better. Here is where things went astray. With a little vacuum (ie. less than 5), torque reported a similar result (ie. <5). Good... BUT wait, once the vacuum moved to about 6 and up, torque reported a vacuum of 18-19... wth!!!! I tried this test an few cycles just see if my eyes and equipment was working. The results were the same each time. Further, the vacuum reading didn't even zero with key off. I had to disconnect the MAP electrically to get back to zero. Certainly a bad device.
So as related to this thread, one should check your vacuum either with torque or with a real gage and then compare the MAP readings at a few "known points"... just seeing a "voltage movement" on the sensor lead does not mean you have a functioning MAP.
I appreciate the response. I haven't had any time to even put the spark plugs back in. I had to take a trip back to my home state and for the last few weeks I've been dealing with pain that i found out yesterday turned out to be a hernia that needs to be surgically repaired. So with patience having ran out, a injury, and temporary being out of work I'm not sure when this will be solved. I plan to replace the broken spark plug and go from there later down the road. If the mods want to close this down it's fine or whenever I do resolve it I can come update incase anyone has a similar issue down the road. I appreciate the 4 pages of help, advise, and knowledge.
@budwich
The MAP that tested as bad with the high readings of 18 or 19.... Was the part number of this device the same as the other(s)?? Anything 'look' different about it, like colors of connectors or seal?
I only have my own vehicle to test against. Is there ~any~ chance you got a 2 or a 3 Bar map in error?
I do me best to make my equations result in values that will match other scanners but there is always the possibility, even the likelihood of my missing the mark.
The MAP that tested as bad with the high readings of 18 or 19.... Was the part number of this device the same as the other(s)?? Anything 'look' different about it, like colors of connectors or seal?
I only have my own vehicle to test against. Is there ~any~ chance you got a 2 or a 3 Bar map in error?
I do me best to make my equations result in values that will match other scanners but there is always the possibility, even the likelihood of my missing the mark.
As with a "number of off shore" buys, the box has a 148464 number which is supposed to be a correct part for the 2008 4.2... but the unit itself has NO markings which I hate. The GM original has a number stamped in the "black plastic" to identify the part. You could be right about the 2-3 bar map issue but seems strange that it would read somewhat correct at low value.
Anyway, I thank you for posting the measurement "technique". I am glad that I went down the path to confirm the bad MAP. Overall, this whole thread helped me make sense of some of the things that I see with fueling / air on the vehicle.
Anyway, I thank you for posting the measurement "technique". I am glad that I went down the path to confirm the bad MAP. Overall, this whole thread helped me make sense of some of the things that I see with fueling / air on the vehicle.
So random thought popped to mind. When I did my long tube headers over a year ago I broke my coolant temperature sensor and the clip on the harness also. I replaced it with a pick a part sensor and come to think of it the sensor is slightly different in the fact the wires from the sensor and the harness aren't the same color but it clipped in fine and my temps read accurate on the cluster and live data. It was a rushed job for a move and has been a after thought. Like I said I can't remember when the codes first started but if it was from that the same time I was running long tubes for the first time and untuned I wouldn't have ever thought of that sensor as a culprit. Just a random thought I had today and wanna see what the more knowledgeable ones say
Mooseman
Moderator
How are the readings? Do they seem to jive? It's possible that a different brand might use different wire colours to the connector. If in doubt, get a new one for your year and model.
