Code P0400

GOCANES

MEMBER
1997 MAZDA 626

This car has had new EGR valve, timing belt, and lots more. The OBDII keeps telling us p0400 and now after refurbished ECU, p0400 (EGR circulation)and now p1400 (DPFE sensor problem). The mechanic has checked everything manually and we cannot seem to figure out what is tripping these codes. Everything checks out fine manually. Should we be looking at something else? This car is costing me more to fix than it is worth. I cannot get the car inspected here because of these check engine codes.

Please help we are out of ideas.

1 Reply

ASEMASTER6371

MECHANIC
52,797 POSTS

Good evening,

The first thing that sticks out about this is that both codes are related to exhaust. The 400 for the DPFE is very common and the usual issue is a clogged cat converter. The exhaust that is not going or allowed through the converter backs up into both the DPFE and the EGR and then these codes set.

https://www.2carpros.com/articles/how-emission-control-systems-work

I would have a back pressure test done on the catalytic converter and I bet you will be told the catalytic converter is clogged and needs to be replaced.

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

Roy

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