EGR trouble code

[Lawrence Quimby]

Anybody good at diagnostics? I keep seeing the same trouble code set on my
1999 Subaru Outback. I have a code reader and it sets a P0400 which
translates to a EGR system malfunction. I've check the EGR system as per the
Haynes manual. I'm leaning towards perhaps the computer is receiving bad
info from one of the O2 sensors and the computer interprets the faulty
signal as an EGR malfunction. Any help?

 

[Alan]

O2 sensors are one of the first things to go on any car today, so it's
possible.

 

[Lawrence Quimby]

Follow-up on EGR problem. It seems to be fixed although I haven't driven
more than 100 miles thus far. I discovered the BPT (backpressure transducer)
valve was defective. When I removed it from it's bracket and shook it water
came out. I called a local tech and asked if there was a way to check it. He
said apply pressure to the exhaust port and it should flow. However apply
vacuum to the same port and it shouldn't. Mine allowed air to travel in both
directions.