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EGR question

posted May 01, 2016 21:09:23 by zracer81
I have a non-EGR head that I just installed onto my 07 Subaru Outback. The engine does have an EGR on it. So my question is this, if I just leave the EGR pipe unconnected but the valve is and open to air would that throw a CEL? When I check the OBD2 list for the 07 Subaru it only has a p0400 which is when there is no flow. The sensor is basically sensing flow, I am not sure if it knows the difference between getting flow from the exhaust port of the head versus flow from atmosphere.

Reason I ask is that I don't want to drill and tap the new head if I don't have to. I will do it though if having the EGR open to atmosphere is going to throw a CEL.

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1 reply
Noah said May 01, 2016 23:59:55
I can't find a good description of how this system monitors egr flow. Some cars will watch the manifold pressure sensor when it activates the egr to determine if there is flow or not, while others have a dedicated temperature sensor in the tube, and others like ford use a differential pressure sensor.
So i guess the answer to your question depends on how the PCM determines when there is egr flow.

I'd refer you to Section 24: EGR system Problems on the free channel
Massachusetts, USA
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