Ford Repair: EGR system, mercury sable, dpfe sensor

Question
1997 Mercury Sable -  EGR circuit

Codes PO401 and PO402 set

All engine connections in normal running position and with KOEO.

When I disconnect the plug from the DPFE sensor and check the harness VREF (BR/W) to ground, I read 5.1 volts.  When I check the harness DPFE (BR/LT. GRN) to ground, I also have 5.1 volts.  Is this normal or do I have a short circuit between the 2 wires?  

Any suggestions on futher testing.

Matt  

Answer
P0401 - Insufficient EGR flow.
P0402 - EGR flow at idle.

We measure the sensor voltage at the PCM, using a breakout box, or with a New Generation Star Tester at the OBDII service port.  I can't confirm or comment on the voltage reading that you are getting, but I don't believe that you have shorted wires.

Replacing a DPFE Sensor is a very common repair for most Ford Vehicles, so common that Ford extended the warranty on this sensor on some vehicles.

Here are some Diagnostic Reference Values from the Service Manual if you want to test the sensor based on the recommended procedure.  Also check that the DPFE vacuum lines are connected properly and in good condition.  EGR Valves almost never go bad, but check that it is operating properly.

VREF = 5.0

DPFE Measured/PID Values
KOEO = 0.2-1.3
Hot Idle = 0.2-1.3
30 MPH = 0.2-4.5
55 MPH = 0.2-4.5

I hope this helps,
Dave