Code 71, Egr Problems? Read This!
05-21-07, 05:08 PM
#1
Driver School Candidate
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Code 71, Egr Problems? Read This!
If you have ever had your "check engine" light and "trac off" light come on because of a CODE 71 (EGR problems) then you might want to read this. I just finished fixing this problem on my car and it was not fun at all. So I figured this might help anyone else who has this problem. This is very long and very in-depth so if you don't want to read it, then you really don't want to attempt to fix this problem yourself. Some of the EGR components on this car are not easy to access!!
First, CODE 71 means there is a problem with the EGR (Exhaust Gas Recirculation) system. The car's ECU can detect if there is a problem with this system by monitoring the EGR temperature sensor. This sensor detects the temperature of the EGR system and therefore knows if there is too little exhaust gas going back into the intake or if there is too much exhaust gas going into the intake manifold.
SYMPTOMS: If you get the code and your car is running rough at idle, it probably means that there is too much exhaust gas going into the intake. That means that the EGR valve is probably stuck open. If you get the code and your car seems to be running fine, then your problem could be a number of things.
DIAGNOSING: First familiarize yourself with the locations of all the components in the EGR circuit.
EGR VACUUM MODULATOR - This is the circular disk near the firewall on the driver side that has P, Q, and R marked on top. This controls the EGR VALVE by regulating the amount of vacuum sent to the EGR valve.
EGR VALVE - This is the circular disk that is near the EGR VACUUM MODULATOR. Find Q on the VACUUM MODULATOR and follow the vaccum line connected to it and you will end up at the EGR VALVE.
VSV - This is located in right next to the intake plenum. It has two vacuum lines coming out of it and has an electrical connector on it. This overrides the EGR VACUUM MODULATOR in certain conditions.
EGR TEMPERATURE SENSOR - This is the connected to the EGR PIPE. This reads the temperature of the exhaust gas that is recirculated to the intake.
STEP 1 - To diagnose what your problem is, I would first invest in a vacuum pump with a gauge. It is well worth the money if you want to figure out your problem. Also, disconnect your battery so that the code clears and that your safe when performing all of this work. First, locate the vacuum hose that comes off of "Q" on the VACUUM MODULATOR. This line splits into two, but follow the line that goes to top of the EGR valve. Disconnect that line on the EGR VALVE and hook up your vacuum gauge to it. This will tell you if your EGR VALVE is working properly. Your engine should start to run rough at about 5" Hg. At more than 5" Hg, your engine should almost die. If nothing happens when you apply full vacuum (about 20" Hg), then either your EGR VALVE is stuck closed, your EGR PIPE is clogged, or the EGR intake inlet is clogged. This scenario is the one you don't want because it will involve lots of labor!!! Skip to Step 6 if your engine doesn't die or run really rough when doing the above test.
STEP 2 - If your car passes the above test, then you are in much better shape because your problem is most likely a bad EGR VACUUM MODULATOR, VSV, EGR TEMP SENSOR, or vacuum line. First, make sure that all of your vacuum lines connected to the VSV, EGR VACUUM MODULATOR, and EGR VALVE are in good condition and not clogged. If so, replace. If not, go to STEP 3.
STEP 3 - Check to see if you have a bad EGR TEMPERATURE SENSOR. The resistance should be 69 - 89 k ohms at 122F, 12-15 k ohms at 212F, and 2 - 4 k ohms at 302F. If the sensor doesn't meet these specs, then the computer may think that there is too much or too little EGR flow.
STEP 4 - First, check to see if you have a bad EGR VACUUM MODULATOR. To do this, take it out of the vehicle. Just remove the vacuum hoses off of "P", "Q", and "R". The slide it out of its holder. Then pull up on it to remove the vacuum hose underneath it. Once you have it out of the vehicle, plug ports "P" and "R" and blow through port "Q". Air should blow pretty freely out of the side of the cap. If not, then the filter under the cap is probably clogged. Take off the cap and check the filter. Now, put a little bit of pressure in the port on the bottom and try the above test again. You should not be able to blow air through "Q" or it should be very hard when there is pressure on the bottom port. If you are still able to blow air through it even with pressure on the bottom, then you have a bad EGR VACUUM MODULATOR. If it passed all of the above tests, then your problem probably isn't the EGR VACUUM MODULATOR.
STEP 5 - Check the VSV. Disconnect both vacuum lines on it and disconnect the electrical connector. Blow air through the port closest to the electrical connector with 12V applied to it and without 12V applied to it. You should be able to blow air through it when the 12V is applied and not able to blow air through it when no voltage is applied . If you are able to blow air through it in both scenarios or if it is blocked in both of the above scenarios, then the VSV is faulty. If it is not faulty, go to STEP 5.
STEP 6 - This is where it gets interesting!! You probably have a bunch of carbon clogging up passages. First, take off the EGR PIPE. This is the pipe that comes from the exhaust manifold and goes into the EGR VALVE. The EGR PIPE is absolutely miserable to take off. There are 2 bolts that hold it into the exhaust manifold that are near the bottom of the engine. You can't get to them from under the car, so you either have to try and snake your hand down there to loosen the bolts or you will have to use a long extension and swivel socket adapter and go at it from an angle. Once have have those two bolts off, you will see the huge nut that connects it to the EGR VALVE. Loosen that nut until the EGR PIPE comes off. Next, take off the EGR VALVE from the Intake Plenum. It is held onto the intake plenum by 2 nuts. Once you have these parts off, inspect them for carbon build up. Make sure to clean everything real good. Also, make sure you take off the elbow on the EGR PIPE that is held on by a screw. That will probably be full of carbon that can block the passage to the EGR MODULATOR. While you have the EGR VALVE out, apply vacuum to the top port and make sure the valve fully stroked and destrokes. Now, here is the judgement call you will need to make. If you found that the EGR VALVE was stuck or that any of the passages were blocked or severely restricted, you might be able to get by and just put everything back on be OK. But, since you have made it this far, you might as well do the next step or else you will be wishing you did if your code comes back.
STEP 7 - You are going to have to take off your intake plenum (the part of the intake that your EGR VALVE is connected to) and clean the passage that the EGR VALVE feeds. In order to do this, you have to remove the air intake, the throttle body, and then the intake plenum. This isn't too bad, but there are a couple nuts that are hard to get to. Also, there is a coolant bypass hose on the bottom of the throttle body that is hard to get off and back on. Once you have it apart, you will see what I am talking about. This passage makes a couple of sharp bends and then ends up in a tube with a small hole in it. You will see how easy it is for carbon to plug this up. Mine was filled with it. You will have to be pretty innovative to clean it. Try and find long pipe cleaning brushes. I used those and coat hangers to try and get from one end of the passage to the other. Cleaning the small hole in the tube is also a challenge. But make sure and spend the time and do it right because more than likely this is your problem. This was the problem on mine. When I did the EGR VACUUM test, my engine speed only slightly decreased because there was almost no exhaust gas going back into the intake. I used a couple of cleaners to help and the best one I found was the STP Intake Cleaner. It worked much better at breaking up the carbon deposits.
STEP 8 - Once you have everything clean, put it all back together. Don't forget to get new EGR gaskets for both the EGR VALVE and PIPE (same part #). Make sure to install the EGR VALVE first before installing the EGR PIPE. The EGR PIPE is very hard to install without the bottom bolts falling out or the gasket falling off. Another tip, when installing the throttle body, use a tie wrap to hold the coolant bypass clamp open so you can slide the hose onto the pipe. One you get the hose on the pipe, just take a screwdriver and pry the tie wrap off.
Hopefully this helps anyone with the annoying CODE 71. I fought this problem for a solid week and I thought I would pass this information onto someone to help. My problem was the clogged EGR intake passage. Looks like the design lends itself to carbon build up after some miles. I cleaned mine up good and everything is good as new!!
First, CODE 71 means there is a problem with the EGR (Exhaust Gas Recirculation) system. The car's ECU can detect if there is a problem with this system by monitoring the EGR temperature sensor. This sensor detects the temperature of the EGR system and therefore knows if there is too little exhaust gas going back into the intake or if there is too much exhaust gas going into the intake manifold.
SYMPTOMS: If you get the code and your car is running rough at idle, it probably means that there is too much exhaust gas going into the intake. That means that the EGR valve is probably stuck open. If you get the code and your car seems to be running fine, then your problem could be a number of things.
DIAGNOSING: First familiarize yourself with the locations of all the components in the EGR circuit.
EGR VACUUM MODULATOR - This is the circular disk near the firewall on the driver side that has P, Q, and R marked on top. This controls the EGR VALVE by regulating the amount of vacuum sent to the EGR valve.
EGR VALVE - This is the circular disk that is near the EGR VACUUM MODULATOR. Find Q on the VACUUM MODULATOR and follow the vaccum line connected to it and you will end up at the EGR VALVE.
VSV - This is located in right next to the intake plenum. It has two vacuum lines coming out of it and has an electrical connector on it. This overrides the EGR VACUUM MODULATOR in certain conditions.
EGR TEMPERATURE SENSOR - This is the connected to the EGR PIPE. This reads the temperature of the exhaust gas that is recirculated to the intake.
STEP 1 - To diagnose what your problem is, I would first invest in a vacuum pump with a gauge. It is well worth the money if you want to figure out your problem. Also, disconnect your battery so that the code clears and that your safe when performing all of this work. First, locate the vacuum hose that comes off of "Q" on the VACUUM MODULATOR. This line splits into two, but follow the line that goes to top of the EGR valve. Disconnect that line on the EGR VALVE and hook up your vacuum gauge to it. This will tell you if your EGR VALVE is working properly. Your engine should start to run rough at about 5" Hg. At more than 5" Hg, your engine should almost die. If nothing happens when you apply full vacuum (about 20" Hg), then either your EGR VALVE is stuck closed, your EGR PIPE is clogged, or the EGR intake inlet is clogged. This scenario is the one you don't want because it will involve lots of labor!!! Skip to Step 6 if your engine doesn't die or run really rough when doing the above test.
STEP 2 - If your car passes the above test, then you are in much better shape because your problem is most likely a bad EGR VACUUM MODULATOR, VSV, EGR TEMP SENSOR, or vacuum line. First, make sure that all of your vacuum lines connected to the VSV, EGR VACUUM MODULATOR, and EGR VALVE are in good condition and not clogged. If so, replace. If not, go to STEP 3.
STEP 3 - Check to see if you have a bad EGR TEMPERATURE SENSOR. The resistance should be 69 - 89 k ohms at 122F, 12-15 k ohms at 212F, and 2 - 4 k ohms at 302F. If the sensor doesn't meet these specs, then the computer may think that there is too much or too little EGR flow.
STEP 4 - First, check to see if you have a bad EGR VACUUM MODULATOR. To do this, take it out of the vehicle. Just remove the vacuum hoses off of "P", "Q", and "R". The slide it out of its holder. Then pull up on it to remove the vacuum hose underneath it. Once you have it out of the vehicle, plug ports "P" and "R" and blow through port "Q". Air should blow pretty freely out of the side of the cap. If not, then the filter under the cap is probably clogged. Take off the cap and check the filter. Now, put a little bit of pressure in the port on the bottom and try the above test again. You should not be able to blow air through "Q" or it should be very hard when there is pressure on the bottom port. If you are still able to blow air through it even with pressure on the bottom, then you have a bad EGR VACUUM MODULATOR. If it passed all of the above tests, then your problem probably isn't the EGR VACUUM MODULATOR.
STEP 5 - Check the VSV. Disconnect both vacuum lines on it and disconnect the electrical connector. Blow air through the port closest to the electrical connector with 12V applied to it and without 12V applied to it. You should be able to blow air through it when the 12V is applied and not able to blow air through it when no voltage is applied . If you are able to blow air through it in both scenarios or if it is blocked in both of the above scenarios, then the VSV is faulty. If it is not faulty, go to STEP 5.
STEP 6 - This is where it gets interesting!! You probably have a bunch of carbon clogging up passages. First, take off the EGR PIPE. This is the pipe that comes from the exhaust manifold and goes into the EGR VALVE. The EGR PIPE is absolutely miserable to take off. There are 2 bolts that hold it into the exhaust manifold that are near the bottom of the engine. You can't get to them from under the car, so you either have to try and snake your hand down there to loosen the bolts or you will have to use a long extension and swivel socket adapter and go at it from an angle. Once have have those two bolts off, you will see the huge nut that connects it to the EGR VALVE. Loosen that nut until the EGR PIPE comes off. Next, take off the EGR VALVE from the Intake Plenum. It is held onto the intake plenum by 2 nuts. Once you have these parts off, inspect them for carbon build up. Make sure to clean everything real good. Also, make sure you take off the elbow on the EGR PIPE that is held on by a screw. That will probably be full of carbon that can block the passage to the EGR MODULATOR. While you have the EGR VALVE out, apply vacuum to the top port and make sure the valve fully stroked and destrokes. Now, here is the judgement call you will need to make. If you found that the EGR VALVE was stuck or that any of the passages were blocked or severely restricted, you might be able to get by and just put everything back on be OK. But, since you have made it this far, you might as well do the next step or else you will be wishing you did if your code comes back.
STEP 7 - You are going to have to take off your intake plenum (the part of the intake that your EGR VALVE is connected to) and clean the passage that the EGR VALVE feeds. In order to do this, you have to remove the air intake, the throttle body, and then the intake plenum. This isn't too bad, but there are a couple nuts that are hard to get to. Also, there is a coolant bypass hose on the bottom of the throttle body that is hard to get off and back on. Once you have it apart, you will see what I am talking about. This passage makes a couple of sharp bends and then ends up in a tube with a small hole in it. You will see how easy it is for carbon to plug this up. Mine was filled with it. You will have to be pretty innovative to clean it. Try and find long pipe cleaning brushes. I used those and coat hangers to try and get from one end of the passage to the other. Cleaning the small hole in the tube is also a challenge. But make sure and spend the time and do it right because more than likely this is your problem. This was the problem on mine. When I did the EGR VACUUM test, my engine speed only slightly decreased because there was almost no exhaust gas going back into the intake. I used a couple of cleaners to help and the best one I found was the STP Intake Cleaner. It worked much better at breaking up the carbon deposits.
STEP 8 - Once you have everything clean, put it all back together. Don't forget to get new EGR gaskets for both the EGR VALVE and PIPE (same part #). Make sure to install the EGR VALVE first before installing the EGR PIPE. The EGR PIPE is very hard to install without the bottom bolts falling out or the gasket falling off. Another tip, when installing the throttle body, use a tie wrap to hold the coolant bypass clamp open so you can slide the hose onto the pipe. One you get the hose on the pipe, just take a screwdriver and pry the tie wrap off.
Hopefully this helps anyone with the annoying CODE 71. I fought this problem for a solid week and I thought I would pass this information onto someone to help. My problem was the clogged EGR intake passage. Looks like the design lends itself to carbon build up after some miles. I cleaned mine up good and everything is good as new!!
Last edited by 94GS300; 05-22-07 at 02:45 AM.
05-21-07, 11:30 PM
#2
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I'm sure this info will be quite helpful for others. If I ever run into this problem, I'll be sure to look this thread up.
Oh and by the way, thanks for all your time and effort into compiling this info. It's very much apprciated
Oh and by the way, thanks for all your time and effort into compiling this info. It's very much apprciated
05-22-07, 01:19 AM
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Wow! Thanks for the terrific troubleshooting guide. I am having this problem right now and have started going through your instructions step by step.
Could you please confirm the instructions in Step 4 where it says "Once you have it out of the vehicle, plug ports "P" and "Q" and blow through port "Q"." Is this a typo? Should I blow through port R instead of Q since I plugged it?
Thanks a million!
Could you please confirm the instructions in Step 4 where it says "Once you have it out of the vehicle, plug ports "P" and "Q" and blow through port "Q"." Is this a typo? Should I blow through port R instead of Q since I plugged it?
Thanks a million!
05-25-07, 03:17 AM
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As a side note I wanted to mention the very wide range in the part's price.
I called 3 different Lexus Dealers and one Toyota dealer in Southern California as well as a dealer in Las Vegas. The lowest price was $72 and the highest was $142 for the SAME part!!! I can't believe this wild price action. It pays to shop around.
05-26-07, 02:34 PM
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How was your car running when the CEL was on? Did it hesitate much when accelerating? How does it run now that the problem is fixed? My CEL is on as well with that same code and my car has been running pretty crappy. I'm wondering if this fix will cause it to run smoother.
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05-28-07, 05:12 AM
#8
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How was your car running when the CEL was on? Did it hesitate much when accelerating? How does it run now that the problem is fixed? My CEL is on as well with that same code and my car has been running pretty crappy. I'm wondering if this fix will cause it to run smoother.
After I fixed mine, I did get quite a jump in gas mileage. I was pleasantly surprised.
01-05-08, 01:00 PM
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My car ran fine when my CEL came on because my EGR valve was stuck closed. An EGR valve stuck closed will not make your engine run poorly at idle, it just increases your risk for "pinging" under load. If your car is running rough and you are getting that code, your EGR valve might be stuck open. Does it run rought at idle? An EGR valve that is stuck open will cause it to run very rough at idle.
After I fixed mine, I did get quite a jump in gas mileage. I was pleasantly surprised.
After I fixed mine, I did get quite a jump in gas mileage. I was pleasantly surprised.
01-09-08, 11:40 PM
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first off, thanks for posting such a detailed write up about this! i know it's asking a lot but i wish there were pictures included, for pictures do speak a thousand words 
anyway, if the EGR valve is stuck closed, would it effect your gas mileage for the worse?
i had a supra before and i deleted the EGR system all together. is there any downside to that? i know there are EGR block off plates to put on the intake manifolds.
if i remember correctly, Deleting the EGR system was HELPFUL for the boosted car for it didn't heat up the 6th cylinder or something of that nature?
it seems that it would be easiest (if smog wasn't an issue) to just delete the system all together! cleaner as well
anyway, if the EGR valve is stuck closed, would it effect your gas mileage for the worse?
i had a supra before and i deleted the EGR system all together. is there any downside to that? i know there are EGR block off plates to put on the intake manifolds.
if i remember correctly, Deleting the EGR system was HELPFUL for the boosted car for it didn't heat up the 6th cylinder or something of that nature?
it seems that it would be easiest (if smog wasn't an issue) to just delete the system all together! cleaner as well
08-12-08, 08:43 AM
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Bump
sorry for the old thread.
Is it easier to follow these steps to clean out EGR, or just buy some na supra blockoff plates, and block the thing off. I'm not super mechanically inclined, so the easier method is preferred...(not to mention we have no emissions testing where i live)
sorry for the old thread.
Is it easier to follow these steps to clean out EGR, or just buy some na supra blockoff plates, and block the thing off. I'm not super mechanically inclined, so the easier method is preferred...(not to mention we have no emissions testing where i live)
09-16-09, 07:47 AM
#15
I'm resurrecting this thread and looking for some answers to questions about EGR systems in general.
I have also just gotten the CEL for the evil Code 71. This troubleshooting guide is fabulous if you can take the time to fix it, but as to consequences of NOT fixing it are what I'd like to ask some of our knowledgable members here.
What happens if you don't fix the EGR when the valve is stuck open/closed? What are the consequences? Bad gas mileage? Something worse?
What does 94GS300 mean when he says there is a better chance of 'pinging' under load?
What are the pros and cons of EGR block off plates? What other methods are there in dealing with the CEL itself or the problem of it reading off EGR values?
I have a boost gauge set up and its been reading odd vacuum values in the manifold for not too long before the CEL came on. Is this an indication of an EGR issue? If so could you explain why?
Answers to one or all would be greatly appreciated
I have also just gotten the CEL for the evil Code 71. This troubleshooting guide is fabulous if you can take the time to fix it, but as to consequences of NOT fixing it are what I'd like to ask some of our knowledgable members here.
What happens if you don't fix the EGR when the valve is stuck open/closed? What are the consequences? Bad gas mileage? Something worse?
What does 94GS300 mean when he says there is a better chance of 'pinging' under load?
What are the pros and cons of EGR block off plates? What other methods are there in dealing with the CEL itself or the problem of it reading off EGR values?
I have a boost gauge set up and its been reading odd vacuum values in the manifold for not too long before the CEL came on. Is this an indication of an EGR issue? If so could you explain why?
Answers to one or all would be greatly appreciated