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p0400 engine code

4550 Views 4 Replies 4 Participants Last post by  1-3-2-4
We've replaced ALL vaccuum lines dealing with EGR, tested EGR and good, EGR solenoid is good, blown and cleared ALL ports regarding EGR, checked metal line for EGR and was clear and code still comes up after running, took to mechanic and he checked and redid everything we did and consulted a fellow mechanic and can't figure it out. What else could it be?
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· Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
19,137 Posts
So, from your post we can determine it is a 1974 to 1999 model Subaru with a boxer engine, unless its a 2001 up H6 with an EGR malfunction or circuit issue.

General questions can only get general answers. EGR systems on Subarus varied in style and function.

How did you check the EGR solenoid?

How did you check the EGR Valve?

Did you check the operation of the transducer?

Do you have an exhaust leak?

Did you check all the electrical plugs and connections for clean and tight? No corrosion?

Have you checked the MAP/BARO sensor?

Did you check the ECM circuits?

Is the 400 code the only one? Are there or were there others? How soon after you drive it does the MIL illuminate?

Depending on the year of the car, and your current weather when this is occurring, there is also a chance that ice is developing in the vacuum hose to the MAP. Subaru had a fix for that.

· Registered
2 Posts
Discussion Starter · #3 ·
we have a 97 imprezza 2.2l auto we checked egr with vac guage. tested solenoid by powering it with 12v and blowing in it and was working good. what you calling transducer? what? how am i checking map/baro sensor? ecm circuits?PLease explain?

· Registered
2014 OBW 3.6R Limited, 1997 OBW 2.5L Auto (sold, but not forgotten), and 1991 Ford F150
1,504 Posts
Transducer = Back Pressure Transducer = BPT

The BPT is a common failure point in the EGR system.

Photo is from 2.5L 97 Legacy OB, but yours should be similar:

tested solenoid by powering it with 12v and blowing in it and was working good
Given that you could blow through it with 12v applied, if you could not blow through it with no power, then it is good.

· Registered
174 Posts
I have a question when blowing into the BPT do I take that hose off on the back of it? I've got the same issue on my 98 Outback I want to narrow it down first before taking off the pipe that heads to the head just because I had issues trying to get the top part off when I did the HG's.
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