Po172 - Chevy Impala Forums
Automotive Discussion General automotive related discussion only.

User Tag List

 9Likes
  • 1 Post By sidemouse
  • 1 Post By Bill58
  • 1 Post By Bill58
  • 1 Post By DBStrings
  • 1 Post By DBStrings
  • 1 Post By Bill58
  • 3 Post By DBStrings
 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 03-15-2019 Thread Starter
Junior Member
 
DBStrings's Avatar
 
Join Date: Mar 2015
Location: Troy NY
Posts: 10
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Thanks: 3
Thanked 0 Times in 0 Posts
Po172

Anyone have some additional tests to help diagnose this trouble code in bank 1 on 2010 Impala w/3.5L?


Trouble Code PO172
Fuel Sys 1 Closed
Calc Load 50.2%
Coolant - 187 F
ST FTRM1 (%) ` 0.0
LT FTRM1 (%) -25.8
MAP (HG) 23.0
Eng Speed (RPM) 1347
VEH Speed (MPH) 52
IGN ADV () 24.0
IAT (F) 52
MAF (LB/M) 2.44
ABSLT (TPS) % 33.3
EVAP Purge 0.0
Fuel Level 44.3%
CLR TRPS 2
CLR DIST (MI) 3
EVAP VP(H2O) -0.231
BARO PRS (HG) 29.5
CAT Temp11 (F) 1148
VPWR (V) 14.883
ABS Load (%) 40.8
CMD EQ RAT 0.999
OUT Temp (F) 50
ABS TPS B (%) 33.3
ACC POS D (%) 28.6
ACC POS E (%) 14.5
THROT CMD (%) 27.8
ALCOHOL (%) 63.5

Also I did a Fuel Pressure Test on the fuel rail and the pressure stayed @ 55 PSI running and during a 10 minute shutdown. If the fuel pressure regulator was faulty i believe i would get a rich condition in both banks?
I'm not getting any misfire codes to show a cylinder is not firing on the rich bank.
The fuel system is also a return-less fuel system.
My thought is because of the negative LTFT would be a rich condition because of to much fuel? Could it be a faulty injector on bank 1? If it was a positive reading my thought was a vacuum leak?
The other two parameters that i question are MAP sensor seems slightly high @ 23.0 and the Alcohol % is content , I think this was a bad test, should i re-test after LTFT returns to normal?

Thoughts?
DBStrings is offline  
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 03-22-2019
Member
 
sidemouse's Avatar
 
Join Date: Feb 2019
Posts: 76
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Thanks: 8
Thanked 6 Times in 6 Posts
Yup, you need to check the Long Term Fuel Trim % which in your case is way low (-25.8%)...
That means your car has cut fuel as much as it can to compensate for the rich condition, and now it can't cut fuel any further so the code appears.
What this does is confirm the code as legitimate, your car is in fact running rich (or at least the sensors have determined that it is).

Your most likely causes:
Dirty or Faulty MAF
Dirty or Faulty Throttle Body
Worn spark plugs
Weak spark plug wires
Vacuum Leak

Your somewhat less likely Causes:
Faulty oxygen sensor
Leaky fuel injectors allowing too much fuel into the combustion cylinders
Stuck fuel pressure regulator
Faulty coolant temperature sensor
Faulty coolant thermostat

There is nothing beyond that I can tell you...
The best I can do is tell you start replacing parts until the code goes away.
I would do it one at a time so you can backtrack if necessary.
sheila likes this.
sidemouse is offline  
post #3 of (permalink) Old 03-22-2019
Senior Member
 
Bill58's Avatar
 
Join Date: Apr 2017
Location: Frederick, MD
Posts: 202
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 44 Post(s)
Thanks: 3
Thanked 22 Times in 22 Posts
Garage
ALCOHOL (%) 63.5
Is that correct? Do you switch between E10 and E85?
Bill58 is offline  
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 03-22-2019 Thread Starter
Junior Member
 
DBStrings's Avatar
 
Join Date: Mar 2015
Location: Troy NY
Posts: 10
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Thanks: 3
Thanked 0 Times in 0 Posts
Sidemouse,
I cleaned the MAF and also the reading is within manufacturers range - MAF 2.44
The throttle body was thoroughly cleaned with almost a full can of cleaner.
The plugs may be worn, but once the car is warm it runs great, no misfires or any additional codes.
I hate to start throwing parts at it, Id like to narrow it down. Im going to do another fuel pressure test and try and find a fuel line to pinch off and see if the pressure bleeds off, that would indicate fuel rail or injectors I believe.

Bill58
No Ive only used standard 87 octane which says E10 on the pump. I agree that reading is super high and I dont know any other way to reset fuel composition and fuel trims, unless I go to the dealer?
DBStrings is offline  
post #5 of (permalink) Old 03-22-2019
Senior Member
 
Bill58's Avatar
 
Join Date: Apr 2017
Location: Frederick, MD
Posts: 202
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 44 Post(s)
Thanks: 3
Thanked 22 Times in 22 Posts
Garage
Quote:
Originally Posted by DBStrings View Post
Bill58
No Ive only used standard 87 octane which says E10 on the pump. I agree that reading is super high and I dont know any other way to reset fuel composition and fuel trims, unless I go to the dealer?
Don't have to go to to the dealer but do need to find a shop with dealer level equipment. ECM thinks you have 63% alcohol so it's increasing injector duty cycle. With E10 engine will run rich.
sheila likes this.
Bill58 is offline  
post #6 of (permalink) Old 03-23-2019 Thread Starter
Junior Member
 
DBStrings's Avatar
 
Join Date: Mar 2015
Location: Troy NY
Posts: 10
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Thanks: 3
Thanked 0 Times in 0 Posts
Bill58,
Do you think that only the ECM is the thing at fault, and the rich condition will return to normal after reprogramming?
DBStrings is offline  
post #7 of (permalink) Old 03-23-2019
Senior Member
 
Bill58's Avatar
 
Join Date: Apr 2017
Location: Frederick, MD
Posts: 202
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 44 Post(s)
Thanks: 3
Thanked 22 Times in 22 Posts
Garage
Quote:
Originally Posted by DBStrings View Post
Bill58,
Do you think that only the ECM is the thing at fault, and the rich condition will return to normal after reprogramming?
GM is at fault, there isn't a alcohol sensor. They cheep-out by calculating the alcohol content using the O2 sensors instead of actually measuring % content.
A good shop may reflash your ECU if there are any updates to avoid future problems.
I would get it taken care of soon. Your cat is eating all the extra fuel and can over heat causing damage the cat.
sheila likes this.
Bill58 is offline  
The Following 2 Users Say Thank You to Bill58 For This Useful Post:
DBStrings (03-25-2019)
post #8 of (permalink) Old 03-24-2019
Member
 
sidemouse's Avatar
 
Join Date: Feb 2019
Posts: 76
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
Thanks: 8
Thanked 6 Times in 6 Posts
Quote:
Originally Posted by DBStrings View Post
Sidemouse,
I cleaned the MAF and also the reading is within manufacturers range - MAF 2.44
The throttle body was thoroughly cleaned with almost a full can of cleaner.
The plugs may be worn, but once the car is warm it runs great, no misfires or any additional codes.
I hate to start throwing parts at it, Id like to narrow it down. Im going to do another fuel pressure test and try and find a fuel line to pinch off and see if the pressure bleeds off, that would indicate fuel rail or injectors I believe.

Bill58
No Ive only used standard 87 octane which says E10 on the pump. I agree that reading is super high and I dont know any other way to reset fuel composition and fuel trims, unless I go to the dealer?
I cleaned my MAF too, didn't change anything...
Then I replaced it, and that fixed the problem.

Just saying...
sidemouse is offline  
The Following User Says Thank You to sidemouse For This Useful Post:
DBStrings (03-25-2019)
post #9 of (permalink) Old 03-24-2019
Junior Member
 
Andre2008's Avatar
 
Join Date: Feb 2019
Posts: 4
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
I also have the P0172 code. 2008 Impala 3.5L Vin K

Observing live data, the engine runs with a bias towards the rich side, but not always so rich as to cause the P0172. Some freeze frame data below.


The sensors (MAP, MAF, ECT, O2) appear to be operating in the desired range. The MAP sensor appears clean. The air filter is clean. The spark plugs were replaced and no improvement was seen.



My system also reports a crazy high Alcohol content, but as this is just calculated I wouldn't expect it to be correct given the rich condition. And it changes all the time (between 40% and 80%). I suspect that if a garage could change it to an appropriate value, it would just calculate and change itself again.



I also have a rough cold start issue - not sure if this is related. The engine will not start and stay started unless I press the accelerator to keep the RPM above 1500 for about 40 seconds. Once warm the car runs and will start without issue. I could not find any vacuum leaks. DBStrings, do you have a cold start issue?



Trouble Code Triggering Freeze Frame: P0172: System Too Rich Bank 1


Freeze Frame Data:
PID : Description : Value
03 : Fuel System Status : Closed loop - using all oxygen sensor(s) as feedback for fuel control
04 : Calculated Engine Load Value : 29.0 %
05 : Engine Coolant Temperature : 92 C, 198 F
06 : Short Term Fuel Trim Bank 1 : -5.5 %
07 : Long Term Fuel Trim Bank 1 : -30.5 %
0B : Intake Manifold Absolute Pressure : 41.0 kPa, 12.1 inHg
0C : Engine RPM : 1415 rpm
0D : Vehicle Speed : 81 km/h, 50 MPH
0E : Timing Advance for #1 cylinder : 41.5
0F : Intake Air Temperature : 9 C, 48 F
10 : Mass Air Flow Rate : 11.41 g/s, 1.51 lb/min
11 : Absolute Throttle Position : 30.2 %
1F : Run Time Since Engine Start : 203 seconds

2E : Commanded Evaporative Purge : 0.0 %
2F : Fuel Level Input : 76.5 %
30 : # of Warm-ups Since Codes Cleared : 1 #
31 : Distance Traveled Since Codes Cleared : 45 km, 28 mile
32 : Evap. System Vapor Pressure : -52.8 Pa, -0.2 inH O ₂
33 : Barometric Pressure : 98 kPa, 29 inHg
3C : Catalyst Temperature Bank 1 - Sensor 1 : 660.0 C, 1220.0 F
42 : Control Module Voltage : 14.343 V
43 : Absolute Load Value : 23.1 %
44 : Commanded Equivalence Ratio : 0.999 λ
45 : Relative Throttle Position : 16.1 %
46 : Ambient Air Temperature : -6 C, 21 F
47 : Absolute Throttle Position B : 30.2 %
49 : Accelerator Pedal Position D : 27.5 %
4A : Accelerator Pedal Position E : 13.3 %
4C : Commanded Throttle Actuator : 23.1 %
52 : Alcohol Fuel % : 74.9 %
Andre2008 is offline  
post #10 of (permalink) Old 03-25-2019 Thread Starter
Junior Member
 
DBStrings's Avatar
 
Join Date: Mar 2015
Location: Troy NY
Posts: 10
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Thanks: 3
Thanked 0 Times in 0 Posts
Yes. On initial start-up i also need to increase the RPM's otherwise it will stall.

Just as BILL 58 said, GM is calculating the alcohol content using the O2 sensors instead of actually measuring % content. There isn't a alcohol sensor

I'm going to make a few calls today and see if i can find a shop to Reset Fuel Composition.

Quote:
Originally Posted by Andre2008 View Post
I also have the P0172 code. 2008 Impala 3.5L Vin K

Observing live data, the engine runs with a bias towards the rich side, but not always so rich as to cause the P0172. Some freeze frame data below.


The sensors (MAP, MAF, ECT, O2) appear to be operating in the desired range. The MAP sensor appears clean. The air filter is clean. The spark plugs were replaced and no improvement was seen.



My system also reports a crazy high Alcohol content, but as this is just calculated I wouldn't expect it to be correct given the rich condition. And it changes all the time (between 40% and 80%). I suspect that if a garage could change it to an appropriate value, it would just calculate and change itself again.



I also have a rough cold start issue - not sure if this is related. The engine will not start and stay started unless I press the accelerator to keep the RPM above 1500 for about 40 seconds. Once warm the car runs and will start without issue. I could not find any vacuum leaks. DBStrings, do you have a cold start issue?



Trouble Code Triggering Freeze Frame: P0172: System Too Rich Bank 1


Freeze Frame Data:
PID : Description : Value
03 : Fuel System Status : Closed loop - using all oxygen sensor(s) as feedback for fuel control
04 : Calculated Engine Load Value : 29.0 %
05 : Engine Coolant Temperature : 92 C, 198 F
06 : Short Term Fuel Trim Bank 1 : -5.5 %
07 : Long Term Fuel Trim Bank 1 : -30.5 %
0B : Intake Manifold Absolute Pressure : 41.0 kPa, 12.1 inHg
0C : Engine RPM : 1415 rpm
0D : Vehicle Speed : 81 km/h, 50 MPH
0E : Timing Advance for #1 cylinder : 41.5
0F : Intake Air Temperature : 9 C, 48 F
10 : Mass Air Flow Rate : 11.41 g/s, 1.51 lb/min
11 : Absolute Throttle Position : 30.2 %
1F : Run Time Since Engine Start : 203 seconds

2E : Commanded Evaporative Purge : 0.0 %
2F : Fuel Level Input : 76.5 %
30 : # of Warm-ups Since Codes Cleared : 1 #
31 : Distance Traveled Since Codes Cleared : 45 km, 28 mile
32 : Evap. System Vapor Pressure : -52.8 Pa, -0.2 inH O ₂
33 : Barometric Pressure : 98 kPa, 29 inHg
3C : Catalyst Temperature Bank 1 - Sensor 1 : 660.0 C, 1220.0 F
42 : Control Module Voltage : 14.343 V
43 : Absolute Load Value : 23.1 %
44 : Commanded Equivalence Ratio : 0.999 λ
45 : Relative Throttle Position : 16.1 %
46 : Ambient Air Temperature : -6 C, 21 F
47 : Absolute Throttle Position B : 30.2 %
49 : Accelerator Pedal Position D : 27.5 %
4A : Accelerator Pedal Position E : 13.3 %
4C : Commanded Throttle Actuator : 23.1 %
52 : Alcohol Fuel % : 74.9 %
sheila likes this.
DBStrings is offline  
post #11 of (permalink) Old 03-27-2019 Thread Starter
Junior Member
 
DBStrings's Avatar
 
Join Date: Mar 2015
Location: Troy NY
Posts: 10
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Thanks: 3
Thanked 0 Times in 0 Posts
Quick Update everyone,
I called around my area and found a couple repair shops that have a TECH-2 scanner or equivalent to what the dealer uses. The cost to perform Fuel Composition reset (Alcohol %) varies from $99.00 +tax to $124.99 +tax
No-one can fit me in until early next week, I'll post if the reset does cure the issue.

One repair shop told me to remove the negative battery cable overnight and it should clear/reset everything. NOPE! It was off initially but came back on during my drive to work.
sheila likes this.
DBStrings is offline  
post #12 of (permalink) Old 03-28-2019
Senior Member
 
Bill58's Avatar
 
Join Date: Apr 2017
Location: Frederick, MD
Posts: 202
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 44 Post(s)
Thanks: 3
Thanked 22 Times in 22 Posts
Garage
Quote:
Originally Posted by DBStrings View Post
One repair shop told me to remove the negative battery cable overnight and it should clear/reset everything. NOPE! It was off initially but came back on during my drive to work.
At least you know which shop not to take it to. Keep us posted.
DBStrings likes this.
Bill58 is offline  
post #13 of (permalink) Old 04-13-2019
Junior Member
 
Andre2008's Avatar
 
Join Date: Feb 2019
Posts: 4
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
DBStrings, were you able to have the Fuel Composition reset?
Andre2008 is offline  
post #14 of (permalink) Old 04-20-2019 Thread Starter
Junior Member
 
DBStrings's Avatar
 
Join Date: Mar 2015
Location: Troy NY
Posts: 10
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Thanks: 3
Thanked 0 Times in 0 Posts
Thumbs up

!UPDATE!

OK I did have a the local shop perform the Fuel Composition Reset a week ago. I wanted to drive it before responding in case the trouble code came back on.

The Reset/Update to the ECU has cleared the trouble code! Using my BlueDriver scan tool the Alcohol Percentage is back at 0%
All the initial startup issues because of to much fuel have gone away, the car is running great.

FYI the shop has a Snap-On scan tool and they charged me $99.00+tax.
plano-doug, sheila and Andre2008 like this.
DBStrings is offline  
post #15 of (permalink) Old 05-13-2019
Junior Member
 
Andre2008's Avatar
 
Join Date: Feb 2019
Posts: 4
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Thanks: 0
Thanked 0 Times in 0 Posts
Great news! Be sure to check into this discussion every now and again to let us know if all continues to run well. You might also want to report the alcohol content from your scan tool.
Andre2008 is offline  
Sponsored Links
Advertisement
 
Reply

Related Threads
Thread Thread Starter Forum Replies Last Post
Po172 DBStrings Automotive Discussion 0 03-18-2019 08:47 AM


Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevy Impala Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome