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Ford Ranger P0401 & P0402

Q. Hi, I have a 1999 Ford Ranger 3.0 Engine. My Check Engine Light came on and the OBD-II code are P0401 and P0402 I changed the EGR valve cleared the codes and the same error came back within a day. I'm not sure where to go from here. Please help.

Ford Ranger P0401 & P0402

A. P0401 is "EGR Flow Insufficient Detected" and P0402 is "EGR FLow Excessive Detected". Two sides of the same coin so to speak.

The possible cause are a bad DPF EGR sensor, a bad EGRVR solenoid or possibly a bad PCM. The first thing to check is the wiring for breaks and be sure the connectors are clean and tight. Also check the vacuum lines for proper routing and that there are no breaks or cracks in them.

The emission system is warranted for 5 years/50,000 miles so if you are within that, you can have Ford fix it.

If not, the procedure for testing the EGR system is a bit long and involved. You can get the procedure from the service manual in the Reference section of your local public library.

Additional Information provided courtesy of ALLDATA

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