Been having issues with theses codes for awhile now
04-29-2021, 06:32 AM
#1
AudiWorld Junior Member
Thread Starter
Been having issues with theses codes for awhile now
i have codes P0171, P0174, P0442, P0441 coming up
For codes P0171 and P0174 I cleaned the original MAF sensor with MAF senor cleaner, codes came back. Bought a new MAF sensor, codes came back. I had the driver side EGR valve replaced about 2 years ago with new OEM part and just recently had the passenger side done with OEM part. Had both codes go away for a few days then they came right back with another code following along which was new to the pile of codes P0420 Which is Catalytic converter related but i have no clue if that is involved with my other code issues. I took a look at the PCV valve and it seems to have good suction and air flow but i have no cleaned or replaced that yet. but At this point i have zero clue what the issue is I NEED HELP!
For Codes P0441 and P0442 i have not tackled the issue yet. Been doing research trying to figure out if its the EVAP Canister or the Leak detection pump or the Purge canister valve. I do get cut off pressure while pumping gas at a gas station, so i have to re-engage the pump handle and i do smell gas from time to time but its not every time i start the car or fill up.
Part numbers and locations of parts are greatly appreciated.
For codes P0171 and P0174 I cleaned the original MAF sensor with MAF senor cleaner, codes came back. Bought a new MAF sensor, codes came back. I had the driver side EGR valve replaced about 2 years ago with new OEM part and just recently had the passenger side done with OEM part. Had both codes go away for a few days then they came right back with another code following along which was new to the pile of codes P0420 Which is Catalytic converter related but i have no clue if that is involved with my other code issues. I took a look at the PCV valve and it seems to have good suction and air flow but i have no cleaned or replaced that yet. but At this point i have zero clue what the issue is I NEED HELP!
For Codes P0441 and P0442 i have not tackled the issue yet. Been doing research trying to figure out if its the EVAP Canister or the Leak detection pump or the Purge canister valve. I do get cut off pressure while pumping gas at a gas station, so i have to re-engage the pump handle and i do smell gas from time to time but its not every time i start the car or fill up.
Part numbers and locations of parts are greatly appreciated.
05-02-2021, 02:22 PM
#3
Could you list the codes you have and the text that comes with them? I'm not gonna Google each and every one to know what they are, and it's not like I have them memorized. What engine you're working on is also pretty relevant. My guess is all the codes comes from the same faulty part.
Have you tried spraying start gas in the engine bay while running to see if it gets sucked in by a vacuum leak? You should hear the rpm increase.
Have you tried spraying start gas in the engine bay while running to see if it gets sucked in by a vacuum leak? You should hear the rpm increase.
05-02-2021, 02:48 PM
#4
AudiWorld Junior Member
Thread Starter
2001 Audi A8L 4.2L Automatic
P0171 - System too lean: (bank 1) Check fuse. Check signal, voltage and ground, Check harness for open or short. Replace MAF sensor. Replace EGR valve or gasket --- To make note i have checked fuses as well.
P0174 - System too lean: (bank 2)
P0441 - EVAP emission control system: incorrect flow
P0442 - EVAP emission control system: small leak
P0420 - Catalyst system: (bank 1) efficiency below threshold
NEW CODE
P0445 - EVAP system: large leak detected
I have not tried spraying start gas in the engine bay while running.
P0171 - System too lean: (bank 1) Check fuse. Check signal, voltage and ground, Check harness for open or short. Replace MAF sensor. Replace EGR valve or gasket --- To make note i have checked fuses as well.
P0174 - System too lean: (bank 2)
P0441 - EVAP emission control system: incorrect flow
P0442 - EVAP emission control system: small leak
P0420 - Catalyst system: (bank 1) efficiency below threshold
NEW CODE
P0445 - EVAP system: large leak detected
I have not tried spraying start gas in the engine bay while running.
05-07-2021, 08:04 AM
#7
AudiWorld Member
You said you have checked MOST of your vacuum lines. Define what MOST means.
Since it appears you may be having vacuum issues, let me invite you to check the vacuum lines that run from the center of the engine to under both headlights to each of your vacuum reservoirs located under each front fender. I have found leaks at the ends of the hoses where they connect to the hard plastic nipples. The ends just split apart from age and heat. The rubber lines are definitely a major item of note. In addition, your vapor canister purge valve located just behind the airbox but near the top of the strut tower is also a good item to replace if you have high mileage. I currently have 342,000 miles on my 2000 A8 40V. My vapor purge valve caused a "incorrect flow code around 20,000 miles ago. Easy fix.
The engine operates with the crankcase in a vacuum. The best way to tell if the vacuum is present is to pull the dipstick while the engine is running and see if you can feel the vacuum by putting your finger over the hole. The engine may even respond or the PCV valve may start making noise. Right now, I have a small vacuum leak UNDER my intake manifold, on the gasket for the oil galley cover. You may also. THE OTHER ITEM IS THE PCV VALVE. I don't have pictures handy, but the diaphragm on the PCV valve is very likely to have a tear in it caused by excessive blow-by if you have a vacuum leak caused by broken hoses. If you have the engine running, remove your top engine cover and place your thumb over the rectangular HOLES on the top of the PCV valve at the back of the motor. Is there a vacuum there? There shouldn't be. If there is a vacuum at all, the diaphragm is ripped and the PCV needs replaced. My advice is NOT to buy the cheapest Chinese made PCV. They may look identical on the outside, but the way the diaphragm is constructed is the real difference. And you can't just pull it apart to inspect the diaphragm without a heat gun and some patience with a flat tip screw driver, otherwise the plastic on the cap will crack, rendering the PCV unusable. It has to have a good seal around the entire circumference to work properly. I'll try to upload pictures later for clarification.
Now as for your catalyst below efficiency, I can tell you that I keep my car maintained. My catalyst efficiency code pops up about every other day or so but no other codes. I do mostly highway driving, I use NON-ETHANOL premium exclusively, and my gas mileage is anywhere between 23.5 and 25.4 MPG depending on if I use the A/C or if I do a bit more idling. The point is that my catalysts are definitely at the end of their life. If you have less than 200,00 miles, the only way that the catalysts are shot is because the engine has been running poorly for too long.
Bottom line: Fix everyone one of your vacuum leaks and you will probably eliminate a bunch of your problems and codes. Replace all possibly bad hoses will new thicker high quality hose with the same inner diameter. It won't route as nicely as the factory stuff, but it will be more resistant to heat.
Since it appears you may be having vacuum issues, let me invite you to check the vacuum lines that run from the center of the engine to under both headlights to each of your vacuum reservoirs located under each front fender. I have found leaks at the ends of the hoses where they connect to the hard plastic nipples. The ends just split apart from age and heat. The rubber lines are definitely a major item of note. In addition, your vapor canister purge valve located just behind the airbox but near the top of the strut tower is also a good item to replace if you have high mileage. I currently have 342,000 miles on my 2000 A8 40V. My vapor purge valve caused a "incorrect flow code around 20,000 miles ago. Easy fix.
The engine operates with the crankcase in a vacuum. The best way to tell if the vacuum is present is to pull the dipstick while the engine is running and see if you can feel the vacuum by putting your finger over the hole. The engine may even respond or the PCV valve may start making noise. Right now, I have a small vacuum leak UNDER my intake manifold, on the gasket for the oil galley cover. You may also. THE OTHER ITEM IS THE PCV VALVE. I don't have pictures handy, but the diaphragm on the PCV valve is very likely to have a tear in it caused by excessive blow-by if you have a vacuum leak caused by broken hoses. If you have the engine running, remove your top engine cover and place your thumb over the rectangular HOLES on the top of the PCV valve at the back of the motor. Is there a vacuum there? There shouldn't be. If there is a vacuum at all, the diaphragm is ripped and the PCV needs replaced. My advice is NOT to buy the cheapest Chinese made PCV. They may look identical on the outside, but the way the diaphragm is constructed is the real difference. And you can't just pull it apart to inspect the diaphragm without a heat gun and some patience with a flat tip screw driver, otherwise the plastic on the cap will crack, rendering the PCV unusable. It has to have a good seal around the entire circumference to work properly. I'll try to upload pictures later for clarification.
Now as for your catalyst below efficiency, I can tell you that I keep my car maintained. My catalyst efficiency code pops up about every other day or so but no other codes. I do mostly highway driving, I use NON-ETHANOL premium exclusively, and my gas mileage is anywhere between 23.5 and 25.4 MPG depending on if I use the A/C or if I do a bit more idling. The point is that my catalysts are definitely at the end of their life. If you have less than 200,00 miles, the only way that the catalysts are shot is because the engine has been running poorly for too long.
Bottom line: Fix everyone one of your vacuum leaks and you will probably eliminate a bunch of your problems and codes. Replace all possibly bad hoses will new thicker high quality hose with the same inner diameter. It won't route as nicely as the factory stuff, but it will be more resistant to heat.
Last edited by spitanddirt; 05-07-2021 at 08:16 AM.
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06-17-2021, 05:28 AM
#8
AudiWorld Junior Member
Thread Starter
P0441 - Incorrect flow (check EVAP valve resistance/ Check for signal, voltage, and ground/ Check harness for open or short and connectors for damage/ check ECM power supply replay/ Replace EVAP valve/ Replace ECM)
P0442 - EVAP emission control system: small leak
P0173 - Fuel trim: malfunction: Bank 2
Here's a little update since last due to the information I've gathered.
My PCV valve was shot. Replaced with a brand new OEM one. Same day I decided to put some Seafoam in my gas tank to see if that would help clear up and clean anything bunged up. (she seemed to run a little smoother after that) Cleared the codes and went on with my week.
Few days later check engine came back popped the code reader/scanner on and only got 1 CODE which was the P0173.
Prior to writing this update I decided to throw the code reader/scanner on the car and i now have those 2 other codes.
Thank you for everyone's help.
P0442 - EVAP emission control system: small leak
P0173 - Fuel trim: malfunction: Bank 2
Here's a little update since last due to the information I've gathered.
My PCV valve was shot. Replaced with a brand new OEM one. Same day I decided to put some Seafoam in my gas tank to see if that would help clear up and clean anything bunged up. (she seemed to run a little smoother after that) Cleared the codes and went on with my week.
Few days later check engine came back popped the code reader/scanner on and only got 1 CODE which was the P0173.
Prior to writing this update I decided to throw the code reader/scanner on the car and i now have those 2 other codes.
Thank you for everyone's help.
06-17-2021, 06:50 AM
#10
Have the (crispy) vacuum lines to the EGR valves been checked? Are the intake manifold vacuum actuators working as expected? With a big vacuum leak these will fail to operate at idle.
N80 valve? Blocking this off might be a good test if it's sucking air when trying to purge, that will cause a lean condition. It will give you codes for EVAP but I would tackle the "system too lean" first. The EVAP leaks can be related to a fuel pump change. Fuel filling problems are often related to a plugged carbon canister.
Cat converter codes can be due to dying cats or bad O2 sensors. I suppose "too lean" could also if the O2s are seriously neglected.
What car is this? Engine, mileage, etc?
N80 valve? Blocking this off might be a good test if it's sucking air when trying to purge, that will cause a lean condition. It will give you codes for EVAP but I would tackle the "system too lean" first. The EVAP leaks can be related to a fuel pump change. Fuel filling problems are often related to a plugged carbon canister.
Cat converter codes can be due to dying cats or bad O2 sensors. I suppose "too lean" could also if the O2s are seriously neglected.
What car is this? Engine, mileage, etc?