check engine light
01-02-2011, 09:31 AM
#1
Audi Forum - Posts like an A3
Thread Starter
Join Date: Oct 2010
Location: Florida
Posts: 51
check engine light
I know I already made a thread about this, and I'm sorry, but I really want this fixed. About couple months ago, when I got my A4, the check engine light came on. Took it to my uncle to have him scan it, trouble code P 401, Exhaust Gas Recirculation Flow Insufficient, or something like that. So we took it to a shop to get it fixed, I know, a bad idea. They wanted like $700 to replace the EGR. I said eff that, I bought a Bentley's Service Manual. Went through, checked the EGR, it worked, they wanted $700 to replace a working part! Checked to see if it was clogged with carbon, nope, clean as a bell. Checked the vacuum lines, no clogs, and no vacuum leaks. Why won't this thing go out?! I did notice that I don't have a check valve going to the EGR, could that be it? Is the sensor bad? It's a damn good thing I love this car . . .
01-02-2011, 11:45 AM
#2
Audi Forum - Posts like an A4
Join Date: Nov 2007
Location: South of Heaven
Posts: 117
Re: check engine light
Using generic codes doesn't give you a lot of info, if you use something like VAG-COM it will give you a specific code with a more detailed explanation. Basically that code is saying your EGR is not working properly and usually this is down to flow. The EGR opens under load and should push the exhaust gases back through the intake to help burn the fuel out of it and the computer in your car knows this is not working properly.
Basic causes can be a EGR valve that is getting old and not working as well as it should. These can test fine when the car is cold but as it heats and expands it may not be opening properly. This is a little harder to test for but I had this with my Corrado as well and corrected it by switching engine management systems to one that didn't use an EGR but this options isn't really available for Audi. If you are getting vacuum leaks in the hoses to the valves or the check valves in the vacuum system it can cause the EGR valve to be lazy and open slowly which could cause this. You can also have soot build-up in the pipes going from the EGR to the intake/exhaust so you may have to clean these out. As the check valve for the EGR this doesn't exist because the EGR is the check valve.
Did the light ever go out or has it been on since you checked it before. It is hard to tell if you made the problem go away for a while or if it has been going the whole time and if it did go away what did you do to make it happen?
Basic causes can be a EGR valve that is getting old and not working as well as it should. These can test fine when the car is cold but as it heats and expands it may not be opening properly. This is a little harder to test for but I had this with my Corrado as well and corrected it by switching engine management systems to one that didn't use an EGR but this options isn't really available for Audi. If you are getting vacuum leaks in the hoses to the valves or the check valves in the vacuum system it can cause the EGR valve to be lazy and open slowly which could cause this. You can also have soot build-up in the pipes going from the EGR to the intake/exhaust so you may have to clean these out. As the check valve for the EGR this doesn't exist because the EGR is the check valve.
Did the light ever go out or has it been on since you checked it before. It is hard to tell if you made the problem go away for a while or if it has been going the whole time and if it did go away what did you do to make it happen?
01-03-2011, 07:29 AM
#3
Audi Forum - Posts like an A3
Thread Starter
Join Date: Oct 2010
Location: Florida
Posts: 51
Re: check engine light
Whenever I had him check it, he always cleared the code. It would come on usually about a week later, normal driving, not driving it hard. It would just come on randomly, and would come on when the car is fully warmed up.
01-03-2011, 02:14 PM
#6
Audi Forum - Posts like an A4
Join Date: Nov 2007
Location: South of Heaven
Posts: 117
Re: check engine light
The do go bad because they work in corrosive exhaust gasses so this is not the first time they will have failed. There are a number of other things you can check into before you start replacing things so do the free things and then start writing cheques.
01-03-2011, 07:49 PM
#8
Audi Forum - Posts like an A1
Join Date: Oct 2010
Location: Ontario
Posts: 28
Re: check engine light
It's been mentioned, but VCDS (VAG-COM) will help you quite a bit with logging values like lambda%, boost pressure values etc, and will often output quite a bit more information about Pxxxx codes.
With a combination of VCDS autoscan/output tests, Ross-Tech's support forum, a Bentley repair manual and various other enthusiast sites, there aren't too many conditions that you can't troubleshoot and repair yourself.
No offense to audiforum.ca, but the engine forums at vwvortex.com would likely be a better place to look when diagnosing engine trouble.
In summary:
1) Purchase VCDS or locate someone locally with the software who works for beer
2) Purchase a Bentley repair manual
3) Scan the car
4) Follow repair procedures in the Bentley manual/research key phrases via Google and forum search functions.
The more specific and thorough you are, the better. If you don't want to take it to a shop, you've got to have at least some of the tools that they'd be using. Submitting a thread on an Audi forum with the title "check engine light" and you might get someone looking to sell you a sticker.
With a combination of VCDS autoscan/output tests, Ross-Tech's support forum, a Bentley repair manual and various other enthusiast sites, there aren't too many conditions that you can't troubleshoot and repair yourself.
No offense to audiforum.ca, but the engine forums at vwvortex.com would likely be a better place to look when diagnosing engine trouble.
In summary:
1) Purchase VCDS or locate someone locally with the software who works for beer
2) Purchase a Bentley repair manual
3) Scan the car
4) Follow repair procedures in the Bentley manual/research key phrases via Google and forum search functions.
The more specific and thorough you are, the better. If you don't want to take it to a shop, you've got to have at least some of the tools that they'd be using. Submitting a thread on an Audi forum with the title "check engine light" and you might get someone looking to sell you a sticker.
01-03-2011, 07:59 PM
#9
Audi Forum - Posts like an A5
Join Date: Oct 2010
Location: Republic of B.C.!
Posts: 382
Re: check engine light
READ BEFORE POSTING: How To Ask Smart Questions
...Before You Ask
Before asking a question do the following:
• Try to find an answer by searching this website.
• Try to find an answer by reading the Bentley Manual. If you don't have one, buy one, you are going to need it.
• Try to find an answer by skimming Audi Forums and pelicanparts.com – both of these are excellent resources you should familiarize yourself with.
• Try to find an answer by inspection or experimentation.
When you post your question, display the fact that you have done these things first; this will help establish that you're not being a lazy sponge and wasting people's time. Better yet, display what you have learned from doing these things. We like answering questions for people who have demonstrated they can learn from the answers.
Search! This might well take you straight to a thread answering your question. Even if it doesn't, saying "I searched on the following phrase but didn't get anything that looked promising" is a good thing to include in your post requesting help.
Prepare your question. Think it through. Hasty-sounding questions get hasty answers, or none at all. The more you do to demonstrate that having put thought and effort into solving your problem before seeking help, the more likely you are to actually get top shelf help.
Beware of asking the wrong question. If you ask one that is based on faulty assumptions, someone is quite likely to reply with a uselessly literal answer while thinking "Stupid question...", and hoping the experience of getting what you asked for rather than what you needed will teach you a lesson.
Never assume you are entitled to an answer. You are not; you don't pay us for the service. However you can (and will) earn an answer, by asking a substantial, interesting, and thought-provoking question - one that implicitly contributes to the experience of the community rather than merely passively demanding knowledge from others.
On the other hand, making it clear that you are able and willing to help in the process of developing the solution is a very good start. "Would someone provide a pointer?", "What test am I missing?", and "What should I have searched for?" are more likely to get answered than "Please post the exact procedure I should use." because in the former examples you're making it clear that you're truly willing to complete the process if someone can just point you in the right direction. In the last you want someone to read you the manual. Go buy one.
How to Search
Search with key words related to your issue. Read the threads that are returned. Modify your search to include new terms you learned from the previous results. This will yield more/different results. Do this, until you have exhausted the variety of terms applicable, and you may just find the answer before you make a new thread. This works on forum searches and Google searches. Try it...
...If You Can't Get An Answer
If you can't get an answer, please don't take it personally that we don't feel we can help you. Sometimes the members of the asked group may simply not know the answer. No response is not the same as being ignored, though admittedly it's hard to spot the difference from outside.
'Bumping' your question more than once every 24 hours is a bad idea. This will be seen as pointlessly annoying. Have patience: the person with your answer may currently be asleep, in a different time-zone, on vacation, etc.
There are also plenty of commercial companies you can go to for help, both large and small. Don't be dismayed at the idea of having to pay for a bit of help! Mechanics & shops exist for reason...
If you can't get an answer, please don't take it personally that we don't feel we can help you. Sometimes the members of the asked group may simply not know the answer. No response is not the same as being ignored, though admittedly it's hard to spot the difference from outside.
'Bumping' your question more than once every 24 hours is a bad idea. This will be seen as pointlessly annoying. Have patience: the person with your answer may currently be asleep, in a different time-zone, on vacation, etc.
There are also plenty of commercial companies you can go to for help, both large and small. Don't be dismayed at the idea of having to pay for a bit of help! Mechanics & shops exist for reason...
...Before You Ask
Before asking a question do the following:
• Try to find an answer by searching this website.
• Try to find an answer by reading the Bentley Manual. If you don't have one, buy one, you are going to need it.
• Try to find an answer by skimming Audi Forums and pelicanparts.com – both of these are excellent resources you should familiarize yourself with.
• Try to find an answer by inspection or experimentation.
When you post your question, display the fact that you have done these things first; this will help establish that you're not being a lazy sponge and wasting people's time. Better yet, display what you have learned from doing these things. We like answering questions for people who have demonstrated they can learn from the answers.
Search! This might well take you straight to a thread answering your question. Even if it doesn't, saying "I searched on the following phrase but didn't get anything that looked promising" is a good thing to include in your post requesting help.
Prepare your question. Think it through. Hasty-sounding questions get hasty answers, or none at all. The more you do to demonstrate that having put thought and effort into solving your problem before seeking help, the more likely you are to actually get top shelf help.
Beware of asking the wrong question. If you ask one that is based on faulty assumptions, someone is quite likely to reply with a uselessly literal answer while thinking "Stupid question...", and hoping the experience of getting what you asked for rather than what you needed will teach you a lesson.
Never assume you are entitled to an answer. You are not; you don't pay us for the service. However you can (and will) earn an answer, by asking a substantial, interesting, and thought-provoking question - one that implicitly contributes to the experience of the community rather than merely passively demanding knowledge from others.
On the other hand, making it clear that you are able and willing to help in the process of developing the solution is a very good start. "Would someone provide a pointer?", "What test am I missing?", and "What should I have searched for?" are more likely to get answered than "Please post the exact procedure I should use." because in the former examples you're making it clear that you're truly willing to complete the process if someone can just point you in the right direction. In the last you want someone to read you the manual. Go buy one.
How to Search
Search with key words related to your issue. Read the threads that are returned. Modify your search to include new terms you learned from the previous results. This will yield more/different results. Do this, until you have exhausted the variety of terms applicable, and you may just find the answer before you make a new thread. This works on forum searches and Google searches. Try it...
