Troubleshooting Egr Codes
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Fleet Mechanic
Joined: Apr 2008
Posts: 1,724
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From: Vancouver BC Canada
Troubleshooting Egr Codes
Not that long ago, I was having some running rich issues that turned out to be fpr and fuel pump related. In the investigating of that problem, I had discovered that the tube that connects the manifold to the egr valve was broken. I jb welded it together and everything has been good for a while (a month or so). Anyway, a couple of weeks ago my check engine light came on and when I pulled the codes it said 172 (hego says system always lean) and 332 (insufficient egr flow detected). I checked the movement on the egr diaphram, sprayed some wd40 on the egr pintle and tested the evp solenoid and harness connector for resitance and voltage as described in the Haynes manual. Everything was within spec as per the manual. I also removed and checked the pvc valve (major pita to put back). Afterwards the truck ran great for a couple of weeks.
Now today, I'm driving and the check engine light comes on again. I pull the codes when I get home and I've got 172 (HEGO says system always lean), 332 (insufficient egr flow detected) and 334 (egr closed voltage higher than expected).
I'm trying to think this through before replacing parts. I'm thinking insufficient vacuum to the egr valve (ie. broken vacuum line) or that egr tube is still leaking. Any thoughts on what the issue might be?
Now today, I'm driving and the check engine light comes on again. I pull the codes when I get home and I've got 172 (HEGO says system always lean), 332 (insufficient egr flow detected) and 334 (egr closed voltage higher than expected).
I'm trying to think this through before replacing parts. I'm thinking insufficient vacuum to the egr valve (ie. broken vacuum line) or that egr tube is still leaking. Any thoughts on what the issue might be?
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
A 334 in CM has nothing to do with voltages, the 334 CM is this:
Continuous Memory DTC 334 indicates the EGR valve was open while the engine was stabilized and at idle sometime during vehicle operation.
Possible causes:
-- EGR valve not seating.
-- EVR solenoid allowing excessive vacuum to EGR valve.
-- Damaged EVP sensor.
PS
Do you have the EGR valve blocked off?
If so you need to drop a penny down the tube under the EGR valve to get rid of this code.
It seems that the exhaust gas can lift the EGR valve off its seat and set this code.
If you were talking about a 334 from the KOEO or KOER self test then it is:
DTC 334 in Key On Engine Off (KOEO) or Engine Running (KOER) Self-Test indicates the EGR valve and/or EGR Valve Position (EVP) sensor may not be fully seated in the closed position. The EVP sensor voltage is greater than the closed limit voltage of 0.67 volt. Because of the preload on the installed EVP sensor, it is difficult to determine whether the EGR valve is seated or the EVP sensor is in contact with the EGR valve stem.
Possible causes:
-- Poor continuity in EVP sensor harness.
-- Non-seated EGR valve.
-- Damaged EGR valve.
-- Damaged EVP sensor.
-- Damaged EVR solenoid.
-- Damaged Powertrain Control Module (PCM).
Fleet Owner
Joined: Jan 2008
Posts: 26,898
Likes: 3
From: southern md
I take it you are talking about a 334 CM.
A 334 in CM has nothing to do with voltages, the 334 CM is this:
Continuous Memory DTC 334 indicates the EGR valve was open while the engine was stabilized and at idle sometime during vehicle operation.
Possible causes:
-- EGR valve not seating.
-- EVR solenoid allowing excessive vacuum to EGR valve.
-- Damaged EVP sensor.
PS
Do you have the EGR valve blocked off?
If so you need to drop a penny down the tube under the EGR valve to get rid of this code.
It seems that the exhaust gas can lift the EGR valve off its seat and set this code.
If you were talking about a 334 from the KOEO or KOER self test then it is:
DTC 334 in Key On Engine Off (KOEO) or Engine Running (KOER) Self-Test indicates the EGR valve and/or EGR Valve Position (EVP) sensor may not be fully seated in the closed position. The EVP sensor voltage is greater than the closed limit voltage of 0.67 volt. Because of the preload on the installed EVP sensor, it is difficult to determine whether the EGR valve is seated or the EVP sensor is in contact with the EGR valve stem.
Possible causes:
-- Poor continuity in EVP sensor harness.
-- Non-seated EGR valve.
-- Damaged EGR valve.
-- Damaged EVP sensor.
-- Damaged EVR solenoid.
-- Damaged Powertrain Control Module (PCM).
A 334 in CM has nothing to do with voltages, the 334 CM is this:
Continuous Memory DTC 334 indicates the EGR valve was open while the engine was stabilized and at idle sometime during vehicle operation.
Possible causes:
-- EGR valve not seating.
-- EVR solenoid allowing excessive vacuum to EGR valve.
-- Damaged EVP sensor.
PS
Do you have the EGR valve blocked off?
If so you need to drop a penny down the tube under the EGR valve to get rid of this code.
It seems that the exhaust gas can lift the EGR valve off its seat and set this code.
If you were talking about a 334 from the KOEO or KOER self test then it is:
DTC 334 in Key On Engine Off (KOEO) or Engine Running (KOER) Self-Test indicates the EGR valve and/or EGR Valve Position (EVP) sensor may not be fully seated in the closed position. The EVP sensor voltage is greater than the closed limit voltage of 0.67 volt. Because of the preload on the installed EVP sensor, it is difficult to determine whether the EGR valve is seated or the EVP sensor is in contact with the EGR valve stem.
Possible causes:
-- Poor continuity in EVP sensor harness.
-- Non-seated EGR valve.
-- Damaged EGR valve.
-- Damaged EVP sensor.
-- Damaged EVR solenoid.
-- Damaged Powertrain Control Module (PCM).
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
If you have blocked off the EGR at its flange and you are getting a 334 code then you can leave it in but do not over tighten the big nut on the tube to deform the tube or the seat.
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Fleet Mechanic
Joined: Apr 2008
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From: Vancouver BC Canada
I think the codes all were in cm. I have a ford code reader that I plug into the eev test connector under the hood and turn the key to the run position. It then cycles through all of the stored codes. No I don't have the egr blocked off. In fact when I JB'ed the egr tube, I put a new gasket in.
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Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
I think the codes all were in cm. I have a ford code reader that I plug into the eev test connector under the hood and turn the key to the run position. It then cycles through all of the stored codes. No I don't have the egr blocked off. In fact when I JB'ed the egr tube, I put a new gasket in.
-- EGR valve not seating.
-- EVR solenoid allowing excessive vacuum to EGR valve.
-- Damaged EVP sensor.
Thread Starter
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Fleet Mechanic
Joined: Apr 2008
Posts: 1,724
Likes: 2
From: Vancouver BC Canada
Ok, so when I combine that list with the 172 (hego always lean) and the 332 (insufficient egr flow detected)...hmm, is it the evp that would trigger the 332? The always lean code leads me to believe that there is too much egr flow, which would fit with the first two possibilities you listed.
But, if the EVP was not registering properly, the EVR might be sending too much vacuum to the egr, causing it to flow when it shouldn't, which could contribute to a lean state. Does that make sense? Maybe you already said that...
But, if the EVP was not registering properly, the EVR might be sending too much vacuum to the egr, causing it to flow when it shouldn't, which could contribute to a lean state. Does that make sense? Maybe you already said that...
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
I would take the EGR valve off and clean it and make sure it can close on its seat.
Put it back on and temporarily drop the penny down the tube and just snug the big nut.
Clear your codes, drive it and see how it runs.
If every thing is OK take the penny out and try it again.
If now the problem comes back it is more than likely the EVR solenoid.
I would then change out the EVR solenoid.
Put it back on and temporarily drop the penny down the tube and just snug the big nut.
Clear your codes, drive it and see how it runs.
If every thing is OK take the penny out and try it again.
If now the problem comes back it is more than likely the EVR solenoid.
I would then change out the EVR solenoid.
Post Fiend
Joined: Apr 2004
Posts: 6,473
Likes: 4
From: Lafayette, IN
Make sure when you clear your codes that you clear the KOEO AND the CM codes--I found that if you pull the jumper wire while the KOEO codes are flashing that only the KOEO codes are cleared--the CM codes are still present. To clear them, you have to run the self-test again and pull the jumper wire while the CM codes are flashing.
Jason
Jason
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