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P0401 and P1151

theoldwizard

New CEG'er
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Oct 19, 2002
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MI
I know the the P0401 is an EGR code and I have confirmed that engine is not getting any EGR so I need to clean the EGR valve, the TBD and ream out the passages ways.

P1151 says EGO #2 (right side, closets to radiator) is lean. Just replaced that O2 sensor. Any other ideas what is causing this code ?
 
If your throwing a lean code, most of the time you've got a minor intake leak somewhere.

However, if you're saying your EGR is not functioning, you would be running lean at light cruise conditions. Your EGR could be the culprit of both codes.
 
...P1151 says EGO #2 (right side, closets to radiator) is lean. Just replaced that O2 sensor. Any other ideas what is causing this code ?
What engine, mileage, and year?

Exactly which O2 sensor was changed?

P1151 is Bank 2 (which is LEFT side of engine aka radiator side) Upper O2 sensor. Sometimes it is listed as the "2-1" sensor.
 
EGR function/no function has no effect on lean/rich. PCM corrects for that..............
 
PCM changes TIMING based on EGR. I would think tune could be cleaner without that effect. As EGR is added, timing advances because now diluted mixture burns slower. Also, diluted burn kills a small amount of power, get some of it back with more advance. In the old days before PCM could adjust for it, when you blocked off EGR, motor often pinged, you had to physically back down the timing. You certainly don't want too much timing while on boost, you're generally looking for some retard as boost comes up.
 
Cleaned out the EGR passages. Previously replaced upper rad side O2 sensor with genuine Bosch sensor. Test ride for 30 minutes from cold start and no CEL.

Car sits for an hour or so and 5 minutes into next ride CEL comes on and P1151 is back.

Now what !
 
when you say previously replaced does that mean awhile ago or when you cleaned the EGR passages?

if you have any sort of significant miles on the O2 sensor then it might need to be replaced again.
 
BrApple - I am correct because it happened to me and these cars with the old style sensor can exhibit this error, P0401 can be the DPFE sensor failure along with the 1400 error codes, or it can be the EGR solenoid, EGR valve failure, or blockage.



"A code P0401 most likely means one or more of the following has happened:
  • The DPFE (feedback EGR) sensor is faulty and needs to be replaced
  • There is a blockage in the EGR (tube), most likely carbon buildup
  • The EGR valve is faulty
The DPFE senor will comunicate to the PCM and the PCM along with other function will activate the EGR solenoid that activates vacuum to the EGR valve.
Try and put a vacuum on the EGR valve itself and see if the symptonms change.

This is where true understanding of the EGR system comes into play. The codes are not always 100% based on the description.
OBDII continiously monitors the DPFE signal, at idle. Since no EGR flow at idle the DPFE signal should show no flow voltage signal. The PCM compares the Key On Engine Off stored voltage to the DPFE signal at idle If the signal is not consistant with this value it may indicate a stuck open EGR valve.

So depending on the state a P04xx code can be thrown or a P14xx code can be thrown.
The P14xx code will be thrown if a negative voltage is detected, or inconsisant values are seen from the DPFE sensor.

So never say never!
 
sure if you talk from a board base, but specific to the contour that isn't correct.

historically here people who have had a P0401 that clean the egr passages behind the tb will clean the code.

yes it could be the sensor but that isn't typical.

if the dpfe has failed, because its the old metal type the typical code is a p0402.

egr valves fail so little that they are normally not of concern on these cars.
 
BRApple, better go readup on Ford DPFE and EGR systems, because it backs up everything I have said, not a broad persepctive at all!

Read my update in my post!
 
BRApple, better go readup on Ford DPFE and EGR systems, because it backs up everything I have said, not a broad persepctive at all!

Read my update in my post!

what I meant in broad perspective is infomration that covers all ford vehicles. from all the troubleshooting what I summarized is normally the end results.


also I'm not talking about the P1400 codes. I am talking about the P0401 and P0402.

cleaning the EGR passages ways normally clear a P0401 code.

a new DPFE normally clears a P0402 code.
 
So am I. As I said knowledge of the EGR system and conditions is needed because set codes might not meet the associated description. P)401 and P0402 is what I was talking about. Depends on set conditions and state of the error!
 
when you say previously replaced does that mean awhile ago or when you cleaned the EGR passages?

if you have any sort of significant miles on the O2 sensor then it might need to be replaced again.
Replaced 3-4 days ago.
 
So am I. As I said knowledge of the EGR system and conditions is needed because set codes might not meet the associated description. P)401 and P0402 is what I was talking about. Depends on set conditions and state of the error!
P0401 is gone after cleaning the EGR gunk around the throttle body.

From what I have read if you still have a P1151 after a recent O2 sensor change that next likely culprit is a vacuum leak.

I'm looking for hints/likely candidates on where a vacuum leak might show up. One old thread replace intake manifold gasket, but that is a lot work. The car drives fine.
 
I'm looking for hints/likely candidates on where a vacuum leak might show up. One old thread replace intake manifold gasket, but that is a lot work. The car drives fine.


but if you go that far you can also complete a intake cleaning which will help the engine run even better in the end. yes it takes about a day but its worth it.
 
Cleaning the throttle body to eliminate the 0401 makes no sense?
Since the PCM executes the monitoring once per driving cycle and takes 70 seconds to post the code along with it has to fail up to a maximum 2500rpm, it will probably rear up it's ugly head again once the state is caught within the designated parameters.
 
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