Finally! A Reason for that damn "31" code
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Logistics Pro
Joined: Jan 2001
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From: Connecticut
Finally! A Reason for that damn "31" code
Finally got rid of the 31 code on my '86 EFI.
New EGR, checked sensor checked air pump valves. all good. Still the 31 EGR system Falt.
Got a Snap on MT2500 scanner. suggested testing the voltage of the brown wire the sensor on top of the EGR.
With KOEO, pierce the brown wire, the voltage in the brown wire has to be between .4 and .6 volts.
Mine was .2V. The snap on came back with.....get this.... "field tecs have found the sensor rod have been ground down to fit mismatched EGR valves. Extend rod to achieve .4 to .6 volts".
so I put 5 layers of fiberglass tape on the tip, (just to test) Erase codes and did a new KOEO, and TA DA! 11, system pass!
Went out and got some grindable epoxy, put some on the tip and tested. Keep filing some off and re-testing till you get to .4 to .6 volts.
Pull off you sensor and inspect the tip. if it is "flat" and has file or grind marks on it, yours too has been ground down at some time in it long past!
New EGR, checked sensor checked air pump valves. all good. Still the 31 EGR system Falt.
Got a Snap on MT2500 scanner. suggested testing the voltage of the brown wire the sensor on top of the EGR.
With KOEO, pierce the brown wire, the voltage in the brown wire has to be between .4 and .6 volts.
Mine was .2V. The snap on came back with.....get this.... "field tecs have found the sensor rod have been ground down to fit mismatched EGR valves. Extend rod to achieve .4 to .6 volts".
so I put 5 layers of fiberglass tape on the tip, (just to test) Erase codes and did a new KOEO, and TA DA! 11, system pass!
Went out and got some grindable epoxy, put some on the tip and tested. Keep filing some off and re-testing till you get to .4 to .6 volts.
Pull off you sensor and inspect the tip. if it is "flat" and has file or grind marks on it, yours too has been ground down at some time in it long past!
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Logistics Pro
Joined: Jan 2001
Posts: 3,789
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From: Connecticut
Local garage has it, I know the guy some, and we worked on this together after hours. I guess it would go for about $2000.00
Pretty cool device. I would have never found that. I fought with "31" for over 2 years!!!!
Pretty cool device. I would have never found that. I fought with "31" for over 2 years!!!!
Posting Guru
Joined: Sep 2003
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From: Right Next to U
Thanks Reamer, I'll give it a try an see what happens, but I believe before I switch out the EGR, it was getting .5 vdc on the brown wire, its worth looking into again tho, and won't hurt to try it.....I'll post the results later.
New User
Joined: Oct 2004
Posts: 8
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From: california
locknkey,
If that doesn't work, I have an EGR valve/sensor with 75K miles on it. I switched it out last week on a trial&error approach. Nothing changed. They're yours (no charge) if you need them.
If that doesn't work, I have an EGR valve/sensor with 75K miles on it. I switched it out last week on a trial&error approach. Nothing changed. They're yours (no charge) if you need them.
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Posting Guru
Joined: Jul 2002
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From: East Coast
Glad to hear you fixed your problem. Now, are you saying you extended the probe going out of the sensor and into the EGR? I don't see why anyone would have ever ground that down, and I know for a fact that my truck had the original sensor and EGR valve on my truck. The wire tested 5v with the wire disconnected, but I didn't do it with it connected and all.
Besides removing the code, did it actually fix any problems with the truck?
I have my egr disconnected right now, and although the problem is much better, it isn't gone.
Besides removing the code, did it actually fix any problems with the truck?
I have my egr disconnected right now, and although the problem is much better, it isn't gone.
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Posting Guru
Joined: Sep 2003
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From: Right Next to U
Thanks Cracker, I had already brought an EGR earier this summer, and it didn't change a thing, Although Reamer Idea might had fixed his, I'm sorry to say it didn't change a thing, still the same code, 11, 10, 31. [EOKO]. I had also disconnected my EGR, and had tested it at 0.5 vdc both on and off positions...when I disconnected my EGR, it had no power, and real bad gas mileage. [ran it for 50 miles and the gas was like it was bogged downed bad too] I reconnected it after that and tested it again, [And dumbed the codes each time, and included the tested as well] no change, same thing codes again. I think the ONLY differenced in Reamers case is that he has a air pump and the air tubes are connected into his manifolds, as mine had already been disconnected and the air pump is gone or either it didn't come with either or both of those components...am still researching this problem and am looking for ANY ideas as to get a 11 someday....mebie.
Posting Guru
Joined: Jul 2002
Posts: 1,147
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From: East Coast
I just checked my new napa sensor and my original sensor. I put the new one in, and I know nobody ever took my original out besides me, and both have the same scratch marks on the bottom. I don't think it was some mechanic with a file, I think it's how they are made.
Personally, my truck can give a code 31 all it wants, as long as it runs ok I don't care. I wonder if it would make it run any better?
Personally, my truck can give a code 31 all it wants, as long as it runs ok I don't care. I wonder if it would make it run any better?
Thread Starter
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Logistics Pro
Joined: Jan 2001
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From: Connecticut
Hi Guys
You have to test the voltage in the brown wire when....
Key on engine off,
Sensor on the EGR....
And plug connected to the sensor.
If the voltage is below 0.4 vlots, then the rod is too short for the EGR.
It was in my case. so I put some of that "grindable epoxy" on the tip and let it harden. after putting it back on the EGR, the voltage was way high. (KOEO, sensor plugged into the sensor)
Ground a little off and re-positioned the sensor a couple of times 'till I got 0.5volts in the Brown wire.
The sensor has to be pluggen in and the key on to measure because the position of the rod shoots the voltage back to the EEC IV through the brown wire. Don't get confused with the voltage being sent TO the sensor, that might be the black wire.
You have to test the voltage in the brown wire when....
Key on engine off,
Sensor on the EGR....
And plug connected to the sensor.
If the voltage is below 0.4 vlots, then the rod is too short for the EGR.
It was in my case. so I put some of that "grindable epoxy" on the tip and let it harden. after putting it back on the EGR, the voltage was way high. (KOEO, sensor plugged into the sensor)
Ground a little off and re-positioned the sensor a couple of times 'till I got 0.5volts in the Brown wire.
The sensor has to be pluggen in and the key on to measure because the position of the rod shoots the voltage back to the EEC IV through the brown wire. Don't get confused with the voltage being sent TO the sensor, that might be the black wire.
Posting Guru
Joined: Jul 2002
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From: East Coast
Thank you reamer!!!!
Thanks reamer! Thanks to your thread my code 31 is now a code 11! There is going to be a lot of happy EEC owners out there tonight! I came up with an easy trick too...
I was taking a shower thinking about the post and it hit me, I threw some clothes on and a handful of change and went out to the garage. I took a small wad of calkstrip (because it's really sticky, I think some kind of weatherstrip adhesive would also work) and stuck it to the back of a nickle, then I stuck it to the top of the diaphram on the inside of the EGR valve. The height of the nickle was just enough! I even reconnected my egr valve. I havn't driven it yet, that will be the real test tommorow, but it sure looks promising. Thanks again for doing the legwork!
I was taking a shower thinking about the post and it hit me, I threw some clothes on and a handful of change and went out to the garage. I took a small wad of calkstrip (because it's really sticky, I think some kind of weatherstrip adhesive would also work) and stuck it to the back of a nickle, then I stuck it to the top of the diaphram on the inside of the EGR valve. The height of the nickle was just enough! I even reconnected my egr valve. I havn't driven it yet, that will be the real test tommorow, but it sure looks promising. Thanks again for doing the legwork!
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Logistics Pro
Joined: Jan 2001
Posts: 3,789
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From: Connecticut
Thaks Great Nickmobile!!
I just wonder if the weight of the nickel will be too much for the vac. to pull up the EGR valve.
If it works, great! if it too much weight. try the grindable epoxie from an auto parts store.
finally, a true code 11!!! 
I just wonder if the weight of the nickel will be too much for the vac. to pull up the EGR valve.
If it works, great! if it too much weight. try the grindable epoxie from an auto parts store.
finally, a true code 11!!!
Thread Starter
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Logistics Pro
Joined: Jan 2001
Posts: 3,789
Likes: 26
From: Connecticut
Thats Great Nickmobile!!
I just wonder if the weight of the nickel will be too much for the vac. to pull up the EGR valve.
If it works, great! if it too much weight. try the grindable epoxie on the tip of the shaft. easily available from an auto parts store.
finally, a true code 11!!!
I just wonder if the weight of the nickel will be too much for the vac. to pull up the EGR valve.
If it works, great! if it too much weight. try the grindable epoxie on the tip of the shaft. easily available from an auto parts store.
finally, a true code 11!!!
Thread Starter
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Logistics Pro
Joined: Jan 2001
Posts: 3,789
Likes: 26
From: Connecticut
Nickmobile, After thinking about your solution, super stickey stuff may not hold up under the super, super hot environment, and the nickel may shift and jam the EGR or worse.