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Ron Z.
Ron Z., - Mercury Tech -
Category: Mercury
Satisfied Customers: 18961
Experience:  18+yrs experience. State Inspector and Mercury Diagnostics
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95 grand marquis: an engine code came of p0402 which..egr system

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i have a 95 grand marquis with the 4.6 engine. an engine code came of p0402 which i understand is the egr system. where is the egr valve and what is the differential pressure switch and where is it located.
Welcome to! My name is DriveFast71(Ron) and I will do my best to answer all of your questions completely and accurately.

With the P0402, very commonly, this is a faulty DPFE Sensor, however, carefully check all of the vacuum lines to the EGR. Carefully check the to lines at the bottom of the DPFE as well. Look for cracks, holes or loose/missing connections. Make sure the EGR Tube is clean and does not have carbon blockage. The EGR Valve is located on the passenger's side, top, rear of the engine. The DPFE is located at the center rear of the engine, near RH side of the intake manifold.
Ron Z., - Mercury Tech -
Category: Mercury
Satisfied Customers: 18961
Experience: 18+yrs experience. State Inspector and Mercury Diagnostics
Ron Z. and 2 other Mercury Specialists are ready to help you
Hello and Welcome to Justanswer,

My name is XXXXX XXXXX I am here to try and assist your with your question

Hi new expert here.

The most common problem is you have a carbon blockage of the egr system. To repair you need to remove the upper intake. or were the throttle body is and there is a u shaped after the throttle body. 4- 8 mm bolts need to be removed and the carbon needs to be removed from the ports that provide exhaust gases down the intake manifold.

Let me know if you need more info or pics. to repair.