Need ask about code p402

Asked by GuruR3HNJ Feb 17, 2020 at 10:30 PM about the 2001 Mercury Grand Marquis LS

Question type: General

Check engine light comes on have code p402. Is
that oxygen sensor

2 Answers
35,525

lrodri911 answered 5 years ago

Most common issues are carbon buildup inside the EGR valve or bad diaphragm inside the EGR valve or cracked vacuum hose to the EGR valve but it can also be triggered by other issues like EVP, DPFE, and MAP sensors. Step 1: Remove it, clean it and inspect diaphragm.

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