Q: diagnose codes

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we have a chevy uplander that is getting four codes p0401,p0402,p0502,p0503 could egr clogged up cause the other codes,about a week ago it acted like it shifted funny but i was almost out of gas put gas in abnd it was fine til a week ago ,fluild was a quart low and now when driving it seems to shift up and down on its on.

My car has 130000 miles.
My car has an automatic transmission.

Hi there. From the codes you are getting it sounds like you do have an EGR issue. It can be caused by a faulty EGR valve or an issue with the EGR system being clogged. This will also give you the other code for the idle issue. I usually test the EGR valve by commanding it on to see if it works. I then remove it and check its ports to see if there is any clogging. I have also seen some circuit issues but that is not as common. If you want to have these codes checked, consider YourMechanic, as a certified mechanic can come to you to [diagnose why the check engine light is on] https://www.yourmechanic.com/services/check-engine-light-is-on-inspection

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