Codes PO401 & PO402 - Focus Fanatics
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Old 02-02-2008, 01:29 PM   #1
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Codes PO401 & PO402

2002 Focus SE 2.0L ZeTec

Pulled codes:
PO401: EGR insufficient flow detected
PO402: EGR excessive flow detected.

Problem is i need a vacuum schematic for this car since the engine emissions decal is missing (car was involved in 2 frontal accidents by the previous owner) I want to check the vacuum system 1st to make sure everything is routed properly but i would need someone to scan the engine emissions decal. I want to start with the basics before "replacing parts" even though it may just be the EGR valve itself. Can anyone supply a schematic and post here?


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Old 02-02-2008, 02:34 PM   #2
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A code P0402 most likely means one or more of the following has happened:

The DPFE (differential pressure) sensor is faulty and needs to be replaced
There is a blockage in the EGR (most likely carbon buildup)
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum

Sorry don't have a vacuum line routing handy! Testing the egr valve itself is easy if you have a vacuum pump. Disconnect the line from the egr, plug the line, connect pump to egr valve, start engine and allow to warm up, apply vacuum to egr valve, you should notice a dicernable difference in the idle speed. If not, then possible bad valve or blockage.
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Old 02-02-2008, 09:34 PM   #3
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Thanks for the tip. I'll post back my findings.
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