Questions and Answers

Ford Windstar DTC P0402 Q. Dear Educated Car Guy, My emission light is on on my 2001 Ford Windstar. I had it diagnostically tested and it read (paraphrasing) "Excessive Flow EGR Valve". Can I repair this myself? I am admittedly a novice but would like to attempt it. I looked on many on-line auto parts sites and had trouble finding an EGR valve. My vehicle has 64,000 miles and is a 3.8 liter. What to do? Thanks, Tom Nashville, TN

A. It is VERY, VERY helpful to include the actual code number when asking. For me to go through some 1,000 odd DTCs to locate one specific code is time consuming and unfair to the others waiting in line.

Anyway, I'm assuming the code is P0402 - EGR Flow Excessive Detected. What this means is the PCM has detected EGR gas flow at idle. The evident symptom in this case would be a rough idle and/or stalling.

There are several cause for this code, among them are:

• The EGR valve is stuck open.
• Plugged EGR vacuum regulator solenoid vent.
• Clogged EGR tube.
• Slow or bad DPF EGR sensor.
• Vacuum lines connected improperly.
• A bad Powertrain Control Module (PCM).

Chances are the EGR valve is stuck open. One way to check is to disconnect the vacuum line from the EGR valve and plug the line. Then drive the car. If the problem is still there, it is a stuck open EGR valve. If it goes away, there is a problem with the EGR vacuum supply system.