Check Engine Light and Code 71
#1
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Check Engine Light and Code 71
Hello everyone,
A few weeks ago my check engine light came on ('92 Xtra Cab DLX 4x4 3VZE) for trouble code 71 (EGR system malfunction).
The first thing I did was visually inspect the hoses to check for obvious cracks/holes. I discovered that one of my hoses between the intake and the EGR modulator was indeed cracked, so I replaced it with some new hose and assumed that would end the issue. I pulled the fuse for the computer, the light went off, after a trip or two the light came back one. I disconnected the battery for a more substantial reset of the computer, the light went off, and after a trip or two, the light came back on.
I proceeded to dig into the FSM for further test procedures and read up on other people's experiences here in the forum. Here is what I've done so far:
Note: my truck doesn't have the EGR temp sensor as part of the system
Tested the EGR valve itself for functionality and/or blockage: PASS
Tested all of the VSV's in the system for functionality, resistance, short circuit: PASS
Tested all hoses for blockage: PASS
Tested for appropriate vacuum at the various locations directed by the FSM: PASS
Tested the EGR modulator for blockage and functionality as directed by the FSM (also removed and cleaned it): PASS
Tested the EVAP system's charcoal canister for blockage and blew compressed air through it to clean it out
I've reset the computer half a dozen times or more at this point and the light keeps coming back on, usually after the 2nd trip in the vehicle (approximately 5-10 miles).
My next thought is to pull the EGR valve off of the engine to give it a clean up and remove any major build up on the port.
I'm wondering if there are any glaring omissions from what I've already done that I should be addressing. And, I'm wondering if the trouble code 71 (despite being specific to the EGR system in its description) would be extended to any of the other parts of the emission system such as the EVAP, PAIR, PCV, or Three Way Cat system.
Thanks in advance for any input or advice.
A few weeks ago my check engine light came on ('92 Xtra Cab DLX 4x4 3VZE) for trouble code 71 (EGR system malfunction).
The first thing I did was visually inspect the hoses to check for obvious cracks/holes. I discovered that one of my hoses between the intake and the EGR modulator was indeed cracked, so I replaced it with some new hose and assumed that would end the issue. I pulled the fuse for the computer, the light went off, after a trip or two the light came back one. I disconnected the battery for a more substantial reset of the computer, the light went off, and after a trip or two, the light came back on.
I proceeded to dig into the FSM for further test procedures and read up on other people's experiences here in the forum. Here is what I've done so far:
Note: my truck doesn't have the EGR temp sensor as part of the system
Tested the EGR valve itself for functionality and/or blockage: PASS
Tested all of the VSV's in the system for functionality, resistance, short circuit: PASS
Tested all hoses for blockage: PASS
Tested for appropriate vacuum at the various locations directed by the FSM: PASS
Tested the EGR modulator for blockage and functionality as directed by the FSM (also removed and cleaned it): PASS
Tested the EVAP system's charcoal canister for blockage and blew compressed air through it to clean it out
I've reset the computer half a dozen times or more at this point and the light keeps coming back on, usually after the 2nd trip in the vehicle (approximately 5-10 miles).
My next thought is to pull the EGR valve off of the engine to give it a clean up and remove any major build up on the port.
I'm wondering if there are any glaring omissions from what I've already done that I should be addressing. And, I'm wondering if the trouble code 71 (despite being specific to the EGR system in its description) would be extended to any of the other parts of the emission system such as the EVAP, PAIR, PCV, or Three Way Cat system.
Thanks in advance for any input or advice.
#2
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If you get code 71 you have an EGR temp sensor, or in the case someone swapped your computer the computer expects this sensor input.
You maybe thinking you don't because you are not in California, this nomenclature is misleading. They produced and sold the California emissions standards outside of California. (Simplicity, costs, ect..)
Do you have an IR temp gun or are you willing to hand test the temperature of the EGR tube where it enters the intake plenum. If it is hot the valve and modulator is presumably working.
EGR temp code 71, is two trip detection. There are very specific instructions in the FSM for the test drive. From memory, you need to be in high gear driving at 55mph for two-five miles, shut off the engine for one to two minutes and repeat the drive.. At your mid test drive pull over spot, hop out and check that EGR pipe it should be hot, very hot not just warm..
Have you done the idle test? (apply vacuum to the EGR valve with the engine idling, it should stall the engine).. If this test fails you either have blockage or the EGR valve isn't moving. Test which one by applying vacuum to the EGR valve and removing the vacuum rapidly you should hear a solid "think" sound as the valve slams shut. If you don't have the think the valve isn't opening and closing properly.
It's possible you have a failed sensor or a dirty plenum.
You maybe thinking you don't because you are not in California, this nomenclature is misleading. They produced and sold the California emissions standards outside of California. (Simplicity, costs, ect..)
Do you have an IR temp gun or are you willing to hand test the temperature of the EGR tube where it enters the intake plenum. If it is hot the valve and modulator is presumably working.
EGR temp code 71, is two trip detection. There are very specific instructions in the FSM for the test drive. From memory, you need to be in high gear driving at 55mph for two-five miles, shut off the engine for one to two minutes and repeat the drive.. At your mid test drive pull over spot, hop out and check that EGR pipe it should be hot, very hot not just warm..
Have you done the idle test? (apply vacuum to the EGR valve with the engine idling, it should stall the engine).. If this test fails you either have blockage or the EGR valve isn't moving. Test which one by applying vacuum to the EGR valve and removing the vacuum rapidly you should hear a solid "think" sound as the valve slams shut. If you don't have the think the valve isn't opening and closing properly.
It's possible you have a failed sensor or a dirty plenum.
#3
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Sensor aside, the output pipe from the EGR valve to the plenum should feel "warm, but not hot." That's pretty imprecise, so that's what the temp sensor measures.
Did you apply vacuum directly to the EGR valve, and detect engine roughness indicating flow? (Step 6 http://web.archive.org/web/201204061...77exhaustg.pdf) At the vintage of our trucks, that valve (and even the part inside the plenum) can get enough gunk to stop the flow, even though everything on the vacuum side is commanding the valve to open.
#4
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Even without a sensor isn't the wiring still in place for the sensor and it has a plug that goes in the end of it, possibly has a built in resistor. Remember seeing someones ride on here a long time ago in stock configuration that did not have a sensor, but the wire was still there and it had an unusual plug in the end.
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Last edited by Andy A; 04-27-2019 at 12:21 PM.
#5
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Yeah, it definitely has me scratching my head.
I'm confident the truck didn't come equipt with the temp sensor based on the state of the port where it would've attached to the valve (doesn't look like anything was ever attached there). Here are some pics, https://imgur.com/a/iO4VSoD). It was originally purchased in Oregon and remained there throughout its life. I definitely didn't remove it or change the ECU. I did perform the vacuum test to the valve and the engine does stumble.
To give a bit more context, in the days leading up to this CEL coming on for the first time, I was installing daytime running lights on the vehicle. In order to install the system, I had to find a power source in the engine compartment that was active when the key was in the "on" position. In order to test for that, I was using a multimeter and a test light on several of the connections (circled in the photos). If one of those circled connectors is for the EGR temp sensor, do you think it's possible that by giving power to it via the test light that I could have somehow triggered the ECU to start expecting the temp sensor to be there, even though the truck never had one? I realize this might be a reach, but based on the timing of the light coming on, I am inclined to think that some of my activity in setting up this DRL system caused this issue.
I'm confident the truck didn't come equipt with the temp sensor based on the state of the port where it would've attached to the valve (doesn't look like anything was ever attached there). Here are some pics, https://imgur.com/a/iO4VSoD). It was originally purchased in Oregon and remained there throughout its life. I definitely didn't remove it or change the ECU. I did perform the vacuum test to the valve and the engine does stumble.
To give a bit more context, in the days leading up to this CEL coming on for the first time, I was installing daytime running lights on the vehicle. In order to install the system, I had to find a power source in the engine compartment that was active when the key was in the "on" position. In order to test for that, I was using a multimeter and a test light on several of the connections (circled in the photos). If one of those circled connectors is for the EGR temp sensor, do you think it's possible that by giving power to it via the test light that I could have somehow triggered the ECU to start expecting the temp sensor to be there, even though the truck never had one? I realize this might be a reach, but based on the timing of the light coming on, I am inclined to think that some of my activity in setting up this DRL system caused this issue.
#6
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Thread Starter
Even without a sensor isn't the wiring still in place for the sensor and it has a plug that goes in the end of it, possibly has a built in resistor. Remember seeing someones ride on here a long time ago in stock configuration that did not have a sensor, but the wire was still there and it had an unusual plug in the end.
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#8
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If you get code 71 you have an EGR temp sensor, or in the case someone swapped your computer the computer expects this sensor input.
You maybe thinking you don't because you are not in California, this nomenclature is misleading. They produced and sold the California emissions standards outside of California. (Simplicity, costs, ect..)
Do you have an IR temp gun or are you willing to hand test the temperature of the EGR tube where it enters the intake plenum. If it is hot the valve and modulator is presumably working.
EGR temp code 71, is two trip detection. There are very specific instructions in the FSM for the test drive. From memory, you need to be in high gear driving at 55mph for two-five miles, shut off the engine for one to two minutes and repeat the drive.. At your mid test drive pull over spot, hop out and check that EGR pipe it should be hot, very hot not just warm..
Have you done the idle test? (apply vacuum to the EGR valve with the engine idling, it should stall the engine).. If this test fails you either have blockage or the EGR valve isn't moving. Test which one by applying vacuum to the EGR valve and removing the vacuum rapidly you should hear a solid "think" sound as the valve slams shut. If you don't have the think the valve isn't opening and closing properly.
It's possible you have a failed sensor or a dirty plenum.
You maybe thinking you don't because you are not in California, this nomenclature is misleading. They produced and sold the California emissions standards outside of California. (Simplicity, costs, ect..)
Do you have an IR temp gun or are you willing to hand test the temperature of the EGR tube where it enters the intake plenum. If it is hot the valve and modulator is presumably working.
EGR temp code 71, is two trip detection. There are very specific instructions in the FSM for the test drive. From memory, you need to be in high gear driving at 55mph for two-five miles, shut off the engine for one to two minutes and repeat the drive.. At your mid test drive pull over spot, hop out and check that EGR pipe it should be hot, very hot not just warm..
Have you done the idle test? (apply vacuum to the EGR valve with the engine idling, it should stall the engine).. If this test fails you either have blockage or the EGR valve isn't moving. Test which one by applying vacuum to the EGR valve and removing the vacuum rapidly you should hear a solid "think" sound as the valve slams shut. If you don't have the think the valve isn't opening and closing properly.
It's possible you have a failed sensor or a dirty plenum.
#9
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I suppose Andy A is onto something; on the non-California trucks they may use the same ECM and harness wiring, just omitting the sensor and replacing it with a 10k ohm (or thereabouts) resistor. It's possible, I suppose, that your EGR is working and you've just mess with the wiring. In which case you could fabricate a 10k ohm resistor to fit into that connector.
I'm against bypassing any of the sensors, but your EGR valve is not tapped for the sensor. So it looks like you never had one.
#10
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Thread Starter
I don't know if this is true. My EWD shows that the 2-pin plug has a BR-B and a G-W wire. Check the wire color on the plugs in your photo. See if you can remember pulling a cap off that plug.
I suppose Andy A is onto something; on the non-California trucks they may use the same ECM and harness wiring, just omitting the sensor and replacing it with a 10k ohm (or thereabouts) resistor. It's possible, I suppose, that your EGR is working and you've just mess with the wiring. In which case you could fabricate a 10k ohm resistor to fit into that connector.
I'm against bypassing any of the sensors, but your EGR valve is not tapped for the sensor. So it looks like you never had one.
I suppose Andy A is onto something; on the non-California trucks they may use the same ECM and harness wiring, just omitting the sensor and replacing it with a 10k ohm (or thereabouts) resistor. It's possible, I suppose, that your EGR is working and you've just mess with the wiring. In which case you could fabricate a 10k ohm resistor to fit into that connector.
I'm against bypassing any of the sensors, but your EGR valve is not tapped for the sensor. So it looks like you never had one.
#11
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Keep in mind that we (at least me) are all speculating about how the ECM works. Before I bought anything like an official plug, I'd try a resistor in the connector. 10k seems to be popular https://www.frys.com/product/7307784, and that's consistent with the temp. curve of the sensor. http://web.archive.org/web/201003261...00egrgaste.pdf
It may or may not be a long term fix for you, but if hooking up the resistor causes the code to go away, you'll know which direction to go.
#12
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No.
Keep in mind that we (at least me) are all speculating about how the ECM works. Before I bought anything like an official plug, I'd try a resistor in the connector. 10k seems to be popular https://www.frys.com/product/7307784, and that's consistent with the temp. curve of the sensor. http://web.archive.org/web/201003261...00egrgaste.pdf
It may or may not be a long term fix for you, but if hooking up the resistor causes the code to go away, you'll know which direction to go.
Keep in mind that we (at least me) are all speculating about how the ECM works. Before I bought anything like an official plug, I'd try a resistor in the connector. 10k seems to be popular https://www.frys.com/product/7307784, and that's consistent with the temp. curve of the sensor. http://web.archive.org/web/201003261...00egrgaste.pdf
It may or may not be a long term fix for you, but if hooking up the resistor causes the code to go away, you'll know which direction to go.
I do remember seeing an actual plug that goes in that connector for those trucks that did not come with a temp sensor.
I did find this statement in an old egr delete thread back in 2010
" Also I didn't have a EGR temp sensor in its place is what looks like to me to be a dud sensor with a resistor in it." Posted by Xeo on 8/9/2010
Last edited by Andy A; 04-27-2019 at 04:47 PM.
#13
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i would try what Scope has suggested, 10k resistors are cheap and you should just be able to bend the ends and plug it into the socket. If it cancels out the CEL your headed in the right direction.
I do remember seeing an actual plug that goes in that connector for those trucks that did not come with a temp sensor.
I do remember seeing an actual plug that goes in that connector for those trucks that did not come with a temp sensor.
#14
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i would try what Scope has suggested, 10k resistors are cheap and you should just be able to bend the ends and plug it into the socket. If it cancels out the CEL your headed in the right direction.
I do remember seeing an actual plug that goes in that connector for those trucks that did not come with a temp sensor.
I did find this statement in an old egr delete thread back in 2010
" Also I didn't have a EGR temp sensor in its place is what looks like to me to be a dud sensor with a resistor in it." Posted by Xeo on 8/9/2010
I do remember seeing an actual plug that goes in that connector for those trucks that did not come with a temp sensor.
I did find this statement in an old egr delete thread back in 2010
" Also I didn't have a EGR temp sensor in its place is what looks like to me to be a dud sensor with a resistor in it." Posted by Xeo on 8/9/2010
#15
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Might try a site like toyotapartsdeal where you can actually plug in your VIN.
Local dealer also.
Really curious as to the part number for that plug and what it is called.
Local dealer also.
Really curious as to the part number for that plug and what it is called.
#16
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Part number is: 82824-35020
#17
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Awesome jordan, hope that does the trick. Thanks for posting up.
Well that sucks, part appears to be discontinued from what I am finding, so unless you find your old one you might be stuck using the 10k resistor.
Well that sucks, part appears to be discontinued from what I am finding, so unless you find your old one you might be stuck using the 10k resistor.
Last edited by Andy A; 04-28-2019 at 05:37 AM.
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Wow! I actually looked "at" that part yesterday, but the description was "CONNECTOR, WIRING HARNESS" https://parts.lakelandtoyota.com/sho...roduct=4193719 so I couldn't tell if it was the one. And as Andy A says, it's long discontinued. https://parts.lakelandtoyota.com/p/_...282435020.html jordanbailey might well be the first person in 25 years to even think of replacing that part ...
#19
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Wow! I actually looked "at" that part yesterday, but the description was "CONNECTOR, WIRING HARNESS" https://parts.lakelandtoyota.com/sho...roduct=4193719 so I couldn't tell if it was the one. And as Andy A says, it's long discontinued. https://parts.lakelandtoyota.com/p/_...282435020.html jordanbailey might well be the first person in 25 years to even think of replacing that part ...
From a knowledge/understanding perspective, what is the difference, functionally, in the EGR system with and without the temperature sensor?
#20
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This has been an interesting case study.
I wonder if there is a way to tell which trucks had the ECU and wiring for the EGR temperature sensor, but never had the sensor itself installed.
I wonder if there is a way to tell which trucks had the ECU and wiring for the EGR temperature sensor, but never had the sensor itself installed.