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Q: I have codes and I need to know what I need to change.

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I have the codes P0300- Random/multiple cylinder misfire detected P0687- control module power relay control circuit/ high P0686- control module power relay control circuit/ low.

I have changed the spark plugs withing the past few weeks. I checked the coils (which are fine) and there is no weird misfire vibrations. Should I change the ecu or the icm? How would I know which if not both to replace? Is it a hard job? How urgent is it to fix? I'm a delivery guy for a Chinese resteraunt so idk if I can drive it for work safely.

My car has 140000 miles.
My car has an automatic transmission.

Hi there:

It’s very difficult to tell you precisely which parts you should replaced simply based on the error codes. A professional mechanic would not only download all trouble codes, but test drive the vehicle to match warning symptoms to the error codes triggered in order to recommend and make the right repairs. Before you invest in purchasing and replacing parts based on your error codes, you might want to have a professional mobile mechanic complete a check engine light inspection first; so they can pinpoint what issues you’re having and recommend the right repairs.

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