Possible causes

– EGR volume control valve stuck open
– Faulty EGR volume control valve
– EGR solenoid valve harness is open or shorted
– EGR solenoid valve circuit poor electrical connection
– Faulty EGR temperature sensor and circuit

Tech notes

There is a factory service bulletin for the following Mercury models:

2000-2002 Mercury Sable
2001-2002 Mercury Cougar
2001-2002 Mercury Grand Marquis
2002-2003 Mercury Mountaineer
Mercury Factory Service Bulletin OBDII Code P0402 Code

When is the code detected?

High Exhaust Gas Recirculation (EGR) flow control is detected

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Possible engine hesitation

P0402 MERCURY Description

Early Exhaust Gas Recirculation (EGR) systems component s include and EGR Valve, and Engine Control