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P0400 code


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10 replies to this topic

#1 matt167

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Posted 03 October 2013 - 01:24 PM

I was driving my '99 SUS, running just fine waiting for the CEL to come on for an evap leak ( filler neck is not healthy, ) and instead it came on for a P0400 which is an EGR code.. I have a spare  EGR and the back pressure transducer  on the original EJ25D manifold. The parts from the EJ22 looked fine so I saw no point in changing.. What is the most common cause of issue with these?  What's weird is it passed the EGR system readiness test but then failed with a code. I only have an OBD Link SX running off a laptop and the software can only scan, it won't force check things like a Snap On or other comparable scanner can, but $50 for it, I won't complain



#2 Fairtax4me

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Posted 03 October 2013 - 11:51 PM

There isn't any electronics associated with the EGR system anyway except the EGR purge solenoid which doesn't provide any feedback to the ECU, so it has no clue what works or doesn't. (It can only tell if the solenoid or worong to it is shorted or open). Even a high end scanner wouldn't help any more than your laptop software in this case.

To determine if the EGR valve is opening and there is actually exhaust gas flowing it has to look for a change in the O2 sensor signal after the EGR valve opens. (Only happens at certain times)

Most of the time the EGR code is due to a bad BPT valve, but it can be caused by bad vacuum hoses/connections.

#3 matt167

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Posted 04 October 2013 - 12:38 PM

Should I change the BPT to see?.. I have the original BPT and EGR from the EJ25D.. I'll recheck the vac lines to be sure



#4 efseiler

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Posted 06 October 2013 - 08:38 AM

Those components are connected so it's unsurprising that one would trigger a code on the other end of the system.  That system is supposed to recirculate tank vapors and exhaust gas back into the intake manifold to insure a most thorough burning of fuel.



#5 Fairtax4me

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Posted 06 October 2013 - 11:45 AM

If you have a spare BPT that only takes a minute to swap so its worth trying. But make sure all of the vacuum hoses that connect to the BPT, the EGR valve, and the EGR solenoid, are in good shape.

EGR and Evap are completely unconnected. All they have in common is the vacuum source.

#6 matt167

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Posted 06 October 2013 - 12:37 PM

Thanks.. BPT is switched with the one originally off the car ( EJ25D manifold ), it definitely looks newer. Spent more time fighting with the bolt on the side getting it lined up than it did to change it out.. The old one had some liquid look in it.. I stuck a wire down the tube into the EGR also. It seemed like it might have been blocked some.. Hopefully this will fix it.



#7 efseiler

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Posted 06 October 2013 - 08:48 PM

If you have a spare BPT that only takes a minute to swap so its worth trying. But make sure all of the vacuum hoses that connect to the BPT, the EGR valve, and the EGR solenoid, are in good shape.

EGR and Evap are completely unconnected. All they have in common is the vacuum source.

 

Are you sure?  I thought the EVAP system was suppose to feed vapors from the tank (which would otherwise be lost to space since no system is completely airtight) into the intake manifold.

 

You'd be suprised...cars are engineered push-pull.  This means a failure on one end of the system can trigger a problem on the other.

 

 

--Damien



#8 efseiler

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Posted 06 October 2013 - 08:59 PM

Thanks.. BPT is switched with the one originally off the car ( EJ25D manifold ), it definitely looks newer. Spent more time fighting with the bolt on the side getting it lined up than it did to change it out.. The old one had some liquid look in it.. I stuck a wire down the tube into the EGR also. It seemed like it might have been blocked some.. Hopefully this will fix it.

 

Yeah, have a look in the hoses connected to the EGR valve...they oftentimes get clogged with carbon deposits.   Try replacing your air filter, too.

 

 

I use additives in my fuel and also apply Seafoam (every car lover's favorite organic solvent) from time to time.

 

 

 

Cheers!

 

--Damien



#9 Fairtax4me

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Posted 06 October 2013 - 10:34 PM

Are you sure? I thought the EVAP system was suppose to feed vapors from the tank (which would otherwise be lost to space since no system is completely airtight) into the intake


--Damien


Yep. You have the right understanding of what they do, but they're not tied to each other in any way.
It wouldn't be good to have a failure of the EGR system forcing exhaust into the fuel tank via the evap system hoses. Or to have unburned fuel vapor being sucked down the EGR piping into the exhaust system.

They have totally separate parts and hoses, and the components even live on opposite sides of the engine.

#10 efseiler

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Posted 08 October 2013 - 04:44 PM

I think ethanol in fuel can also trigger such a code cuz it alters the vapor pressure.

 

 

--Damien



#11 later_Peter

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Posted 08 October 2013 - 05:22 PM

threw a P0400 code last week. took EGR valve out. cleaned it the best I could. (Seafoam DeepCreep & Carb/Choke cleaner) used an old toothbrush until I could see all metal... put it back & no codes for the past week... (it was pretty well carboned up)






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