My car has the check engine light on and the code reader states that is P0400. I looked through other posts here and have tried things mentioned in the posts that seem to be related. The code comes back after a reset. The CEL takes a while to come back on, maybe around 50 miles of city and highway driving. Here is what I have done:

1. Checked the resistance between terminals on the electrical connection of the EGR valve. 22 Ohms was indicated between the terminals as specified in another post.

2. Remove the EGR valve andcleaned thevalve passages.

3. The vacuum port next to the EGR was a little plugged so I cleaned it as well. The port pulls a good vacuum when car is running.

4. Cleaned the connections on the valve and the boost sensor.

- Is there any other way to test the EGR and the boost sensor components?

- What else should I check?

- There is no vacuum being pulled outof the other port on the boost sensor (plastic component that the vacuum line near the EGR valve goes to). Should there be?

I am very mechanically inclined and am willing toattempt anything suggested.
Thanks for any help you can supply.

Mike

 

Is the measurement you give in your first statement is the resistance on the EGR valve position sensor? If so, according to the shop manual, the specification is 2.7 Kiloohm, or 2700 ohms. If this is correct this might be leading us to the EGR valve.

The other thing you want to check is that there is no cracks or damage in theEGR boost sensor. If this doesn't hold vacuum, then it will show as a failure.

Ihad a problem with P1195 code. I cleaned out the ports and such,problem came back. I went the boneyard and pulled Boost sensor and solenoid($5) and replaced, problem solved. The hardest part was getting the aluminum nuts off the steel firewall. Bring WD40.

The shop maunal basically says anything in the EGR line could have malfunctioned, but remember, this code is a flow malfunction, look toward things that are blocked first.

The boost sensor (Plastic part) should just have one hose going to it. There should be no vacuum coming out of the sensor.

 

Looking back at my post I incorrectly stated "boost sensor" when I meant the selenoid next to the boost sensor. The selenoid has two hoses and the boost sensor has only one.

The resistance I checked was on the six pin connector on the EGR valve as mentioned in this post:

https://www.mazdaforum.com/archive/t...ge-4880-1.html

Is this the EGR valve position sensor? If so, what connectors are you measuring across to get the 27Kohms value. I measured
C->A, C->E, D->B, D->F as mentioned in the above post.

I should also mention that the car is running fine but since I need to have an emissions inspection within the next few weeks I need to solve this problem (too bad it did not wait a couple of weeks to occur).

Thanks again for your time,

Mike