p0172 error code
03-26-2022, 08:57 PM
#1
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Join Date: 03-03-2022
Location: USA
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p0172 error code
hello
i have a 09 hhr lt i ran it through a scanner and got a p0172 code
i found when i add e85 fuel the code disappears and the car runs fine.
the problem is i want to use regular fuel but when i do the car runs rough and the check engine light comes on. with the scanner it says i am using e85 when in fact im using regular gasoline.
can anyone point me in the right direction to remedy this problem? thanks for your help in advance
i have a 09 hhr lt i ran it through a scanner and got a p0172 code
i found when i add e85 fuel the code disappears and the car runs fine.
the problem is i want to use regular fuel but when i do the car runs rough and the check engine light comes on. with the scanner it says i am using e85 when in fact im using regular gasoline.
can anyone point me in the right direction to remedy this problem? thanks for your help in advance
03-27-2022, 07:51 AM
#3
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Join Date: 01-23-2009
Location: Fredericksburg,VA
Posts: 24,736
First, I would try a new #1 O2 sensor, if someone replaced it in the past they may have used the wrong one.
Second, A GM service dept or someone that knows how and has the computer can reset the ECM.
Second, A GM service dept or someone that knows how and has the computer can reset the ECM.
03-27-2022, 02:28 PM
#4
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Join Date: 12-05-2014
Location: Northern Ohio
Posts: 2,375
P0172 means the car thinks the trim needed to correct a rich mixture is excessive.
Went through this. A bit of discussion in two or three threads here, including one I initiated.
My 2011 (flex fuel like yours) decided it had over 50% ethanol in the tank, even though it was really 10%, basically exactly what the regular out here is expected to be. Initially it was probably worse; the car may have already begun correcting itself by the time I got a sample to test.
Betcha this is the case with yours.
The first sign was a crank/no start. Turns out it WOULD start in flood-clearing mode, holding pedal to the floor. The car was trying to start with a mix far to rich, because it though it had all that ethanol. Upon startup it would smoke and sputter, but once it the coolant hit about 110F it ran fine.
The cure was having the store ethanol level reset to zero. But I did NOT have E85 in the tank.
I found other cases just like this online with other GM FlexFuel cars and trucks.
ALWAYS turn of the car when fueling. The car needs this to prompt it to try to calculate the ethanol % it now has in the tank. There is no ethanol sensor. It deduces the alcohol % in part from O2 sensors readings. Pretty sure the entire evap and emission system needs to be near perfect or it could have trouble with this. So Donbrew’s suggestion that a bad O2 sensor could contribute is not unreasonable.
It’s possible that you could refuel with regular with the engine off and everything will be fine.
A lot of inexpensive scanners can tell you what the stored ethanol% is, although it’s often cleverly buried in the menus. High-end tools can reset it too. Mine read it fine, but I went to the dealer to reset it. With understanding and luck you may be able to avoid that.
I had a fuel line leak concurrent to this problem. I suspect that may have contributed.
Lots of very short trips and no long ones seems to be associated with this problem.
What do you think of all that? How many times have you switched fuels back and forth?
Went through this. A bit of discussion in two or three threads here, including one I initiated.
My 2011 (flex fuel like yours) decided it had over 50% ethanol in the tank, even though it was really 10%, basically exactly what the regular out here is expected to be. Initially it was probably worse; the car may have already begun correcting itself by the time I got a sample to test.
Betcha this is the case with yours.
The first sign was a crank/no start. Turns out it WOULD start in flood-clearing mode, holding pedal to the floor. The car was trying to start with a mix far to rich, because it though it had all that ethanol. Upon startup it would smoke and sputter, but once it the coolant hit about 110F it ran fine.
The cure was having the store ethanol level reset to zero. But I did NOT have E85 in the tank.
I found other cases just like this online with other GM FlexFuel cars and trucks.
ALWAYS turn of the car when fueling. The car needs this to prompt it to try to calculate the ethanol % it now has in the tank. There is no ethanol sensor. It deduces the alcohol % in part from O2 sensors readings. Pretty sure the entire evap and emission system needs to be near perfect or it could have trouble with this. So Donbrew’s suggestion that a bad O2 sensor could contribute is not unreasonable.
It’s possible that you could refuel with regular with the engine off and everything will be fine.
A lot of inexpensive scanners can tell you what the stored ethanol% is, although it’s often cleverly buried in the menus. High-end tools can reset it too. Mine read it fine, but I went to the dealer to reset it. With understanding and luck you may be able to avoid that.
I had a fuel line leak concurrent to this problem. I suspect that may have contributed.
Lots of very short trips and no long ones seems to be associated with this problem.
What do you think of all that? How many times have you switched fuels back and forth?
03-28-2022, 06:54 AM
#5
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Join Date: 03-03-2022
Location: USA
Posts: 16
thanks for the suggestions.
the scanner says i had 51% alcohol in my tank when in fact I used unleaded regular gasoline.
I never add fuel to a vehicle that's running just because of the hazards that can happen mainly I don't want to catch fire secondly don't want any error codes that can happen from fueling a running car.
the o2 sensor could be the issue. there were a couple other codes can't recall the code numbers, but they were for the exhaust cam positioning sensor, so I changed both the exhaust and intake cam position sensors. another code was for the downstream o2 sensor, I got the part number from Napa Autoparts but actually got the sensor from Ebay motors. the sensor i received had the correct name and numbers on the box but it was different from the sensor I removed. the wire colors and the plug were the same, but the sensor itself was longer it barely fit between the exhaust pipe and the frame/body of the car. I still had the old o2 sensor so i tried switching it with the new one thinking it would throw a code while letting the car run normally but that didn't happen. with the old o2 sensor in the code didn't come back nor did the rough idle disappear.
I don't want to start changing unnecessary parts. I read a thread where someone changed pretty much changed everything, they could under the hood only to find out they needed to reset the alcohol percentage
after checking the alcohol percentage, the computer thinks I am using 51% alcohol gasoline when I am using 87 octane gasoline, at least that is what the pump says. With the regular gasoline i get a p0172 code and car has a hard start, smells like straight gas fumes are coming in the cabin and runs rough until it warms up.
When i put e85 fuel in it the check engine light goes off and the car runs fine even the remote start works. I don't have a scanner that can reset the alcohol percentage so, I guess 1 option would be to find a shop that can and is willing to reset the alcohol percentage.
I was reading that if I fill the tank with at least 3 gallons of high-grade gasoline it should reset the alcohol percentage, I guess that could be option 2, has that worked for anyone with this issue?
I had several people tell me to disconnect the battery touch the wires together and leave it unplugged for 20-30 minutes. is this really another option? if so, has anyone tried it? did it work?
Again, thank you all for your time and I appreciate not hearing/seeing use the search function
the scanner says i had 51% alcohol in my tank when in fact I used unleaded regular gasoline.
I never add fuel to a vehicle that's running just because of the hazards that can happen mainly I don't want to catch fire secondly don't want any error codes that can happen from fueling a running car.
the o2 sensor could be the issue. there were a couple other codes can't recall the code numbers, but they were for the exhaust cam positioning sensor, so I changed both the exhaust and intake cam position sensors. another code was for the downstream o2 sensor, I got the part number from Napa Autoparts but actually got the sensor from Ebay motors. the sensor i received had the correct name and numbers on the box but it was different from the sensor I removed. the wire colors and the plug were the same, but the sensor itself was longer it barely fit between the exhaust pipe and the frame/body of the car. I still had the old o2 sensor so i tried switching it with the new one thinking it would throw a code while letting the car run normally but that didn't happen. with the old o2 sensor in the code didn't come back nor did the rough idle disappear.
I don't want to start changing unnecessary parts. I read a thread where someone changed pretty much changed everything, they could under the hood only to find out they needed to reset the alcohol percentage
after checking the alcohol percentage, the computer thinks I am using 51% alcohol gasoline when I am using 87 octane gasoline, at least that is what the pump says. With the regular gasoline i get a p0172 code and car has a hard start, smells like straight gas fumes are coming in the cabin and runs rough until it warms up.
When i put e85 fuel in it the check engine light goes off and the car runs fine even the remote start works. I don't have a scanner that can reset the alcohol percentage so, I guess 1 option would be to find a shop that can and is willing to reset the alcohol percentage.
I was reading that if I fill the tank with at least 3 gallons of high-grade gasoline it should reset the alcohol percentage, I guess that could be option 2, has that worked for anyone with this issue?
I had several people tell me to disconnect the battery touch the wires together and leave it unplugged for 20-30 minutes. is this really another option? if so, has anyone tried it? did it work?
Again, thank you all for your time and I appreciate not hearing/seeing use the search function
03-28-2022, 07:15 AM
#7
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Join Date: 12-06-2009
Location: Alabama
Posts: 11,110
Quote :"there were a couple other codes can't recall the code numbers, but they were for the exhaust cam positioning sensor, so I changed both the exhaust and intake cam position sensors. "
Well. Chances are you may have replaced the wrong parts for this. Many code readers will say it is the cam position sensor for P0010, P0011, P0013, P0014. The faulty part is usually the intake or exhaust actuator solenoids. Not the cam position sensor.
Would be nice to know those actual code numbers. Any chance they're still there and not erased ?
Well. Chances are you may have replaced the wrong parts for this. Many code readers will say it is the cam position sensor for P0010, P0011, P0013, P0014. The faulty part is usually the intake or exhaust actuator solenoids. Not the cam position sensor.
Would be nice to know those actual code numbers. Any chance they're still there and not erased ?
03-28-2022, 12:01 PM
#9
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Join Date: 12-05-2014
Location: Northern Ohio
Posts: 2,375
Sampling the contents if the tank and testing the ethanol content is not that hard. Google or ask here if you need help.
Last edited by PulpFriction; 03-29-2022 at 02:37 AM.
03-28-2022, 02:17 PM
#10
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Join Date: 03-03-2022
Location: USA
Posts: 16
thanks for the input
timing chain could be a possibility
touching wires seems like it could lead to more problems
looked at some videos on ethanol testing of gasoline seems like a straightforward process
as far as the codes go i lost that info.
just trying to remember when i looked the codes up the possible causes was faulty bank 1 o2 sensor 2
maybe a p313 code or something like that when i looked the code up a possible code was a camshaft sensor i think it was the exhaust code but changed both the intake and exhaust camshaft positioning sensor
il look for the codes again i know i have them somewhere. after the fixes i used a different scanner and the previous codes from the other scanner were gone and the p0172 code was thrown and the car ran rough. before the changes the car ran fine i just didnt like the check engine light on. somewhere between the o2 sensor and the battery dying started the p0172 code. I'm leaning towards the o2 sensor only because it is longer than the one it replaced and I don't know if that makes a difference i assumed it didnt matter because the code disappeared
once i find the codes ill report back
timing chain could be a possibility
touching wires seems like it could lead to more problems
looked at some videos on ethanol testing of gasoline seems like a straightforward process
as far as the codes go i lost that info.
just trying to remember when i looked the codes up the possible causes was faulty bank 1 o2 sensor 2
maybe a p313 code or something like that when i looked the code up a possible code was a camshaft sensor i think it was the exhaust code but changed both the intake and exhaust camshaft positioning sensor
il look for the codes again i know i have them somewhere. after the fixes i used a different scanner and the previous codes from the other scanner were gone and the p0172 code was thrown and the car ran rough. before the changes the car ran fine i just didnt like the check engine light on. somewhere between the o2 sensor and the battery dying started the p0172 code. I'm leaning towards the o2 sensor only because it is longer than the one it replaced and I don't know if that makes a difference i assumed it didnt matter because the code disappeared
once i find the codes ill report back