Manifold Pressure Diferential Sensor (MDP) testing

[FooseGalant]

Been chasing a P0400 EGR CEL code on my 2000 V6 Galant ES (Fed Spec). Took it to the dealer after I tested all the components that the manual said to check that were located under the hood. They all passed. The tech at the dealer said the failure was the MDP sensor and they replaced it. It popped the code again within 20 miles. At dealer for second time and they said that they had left a vacuum line off the EGR valve and there was moisture in the EGR. Cleaned and assembled completely, I was off driving again for 20 miles...and the CEL popped again.

Question - How do I test the MDP sensor? I can't find anything in the manual about it. The $160 part did not fix the problem. Did not know it was part of the EGR system. Changed the gas cap also and that had no effect.

Any suggestions?

UPDATE - After another 3 hours at the dealer (1 hour on the phone with the factory experts) they feel they have tracked down the issue. There seems to be a check valve in one of the EGR pipes. The one with a yellow mark on it. They said it is like a wire mesh ball that that will restrict air flow but not shut it under certain conditions. I guess it just ate it or it was damaged in the cleaning process while checking the pies for blockages. They have ordered the pipe cluster (only 3 left in the US). We will see if this fixes the issue and the P0400 code does not come back. Part due 1/5/16.

Has anybody else run across this issue with V6 Galants?

Thanks

[FooseGalant]

Just got back from the dealer and the P0400 code seems to be fixed. The dealer solution to replace the spaghetti tubes in the EGR system has, for the time being, fixed the check engine light. There is a check valve in one of the flexible lines (see photo) that deteriorated and caused the CEL. The tubes were clear and fee of contaminates and did not contribute to the failure code. If you are having an issue with the EGR, this could be the cause. A check valve is not listed anywhere in the manual. The dealer was not aware of its existence either. Only after more than an hour on the phone with Mitsubishi support was the potential solution identified.



GREEN MARKED TUBE TO VACUUM CONTROL VALVE contains the check valve but is not noted.

[PR8GG]

I want to ask you, from your experience with this issue; do you notice an unusual gas consumption? I ask because I am having the same issue, (and same code) but with my 4 cil. Galant, and its being swallowing gas like a V12!

[FooseGalant]

Yes, the miles per gallon was down about 20%. I just did the first cold start since the repair was done. The check engine light has not popped again. I will have to put some miles on it in the next week to see if the mileage improves and will post an update. I do not know for sure if your 4 cyl has the check valve and I can't check the manual as Mitsubishi elected to leave that information out on both the 4 and 6 cyl models.

I want to ask you, from your experience with this issue; do you notice an unusual gas consumption? I ask because I am having the same issue, (and same code) but with my 4 cil. Galant, and its being swallowing gas like a V12!