My wifes 1996 Explorer 5.0 threw a code of PO402. Track record of a failing DPFE sensor will print out this code. My proble is, I cannot locate it either in the engine compartment or on the vacuum diagram. But have to admitt, my 02, 4.2 F150 doesn't have it in the vacuum diagram either. Any ideas or direction is appreciated. I can purchase whats needed, if anything on Monday or Tuesday, but work on the vehicle some 45 miles from any parts house or dealership. Thanks and will erase any $50.00 tab for info offered up in the past or will issue credit for the future.

 

Is this what you need?

 

Here is the info from the Ford. I can't provide pics, but maybe this will help.

The Differential Pressure Feedback EGR Monitor is an on-board strategy designed to test the integrity and flow characteristics of the EGR system. The monitor is activated during EGR system operation and after certain base engine conditions are satisfied. Input from the ECT, IAT, TP and CKP sensors is required to activate the EGR Monitor. Once activated, the EGR Monitor will perform each of the tests described below during the engine modes and conditions indicated. Some of the EGR Monitor tests are also performed during on demand self-test.
The D.P.F. EGR sensor and circuit are continuously tested for opens and shorts. The monitor looks for the DPFE circuit voltage to exceed the maximum or minimum allowable limits.
The DTCs associated with this test are DTCs P1400 and P1401.
The EGR Vacuum Regulator Solenoid is continuously tested for opens and shorts. The monitor looks for an EVR circuit voltage that is inconsistent with the EVR circuit commanded output state.
The DTC associated with this test is DTC P1409.
The test for a stuck open EGR valve or EGR flow at idle is continuously performed whenever at idle (TP sensor indicating closed throttle). The monitor compares the DPFE circuit voltage at idle to the DPFE circuit voltage stored during key on engine off to determine if EGR flow is present at idle.
The DTC associated with this test is DTC P0402.
The DPFE sensor hoses are tested once per drive cycle for disconnect and plugging. The test is performed with EGR valve closed and during a period of acceleration. The PCM will momentarily command the EGR valve closed. The monitor looks for the DPFE sensor voltage to be inconsistent for a no flow voltage. A voltage increase or decrease during acceleration while the EGR valve is closed may indicate a fault with a signal hose during this test.
The DTCs associated with this test are DTCs P1405 and P1406.
The EGR flow rate test is performed during a steady state when engine speed and load are moderate and EVR duty cycle is high. The monitor compares the actual DPFE circuit voltage to a desired EGR flow voltage for that state to determine if EGR flow rate is acceptable or insufficient.
The DTCs associated with this test are DTCs P0401 and P1408.
The MIL is activated after one of the above tests fail on two consecutive drive cycles.

Figure 9: EGR Monitor - Differential Pressure Feedback

Exhaust Gas Recirculation (EGR) Monitor Sonic EGR - (Probe)

The Sonic EGR Monitor is an on-board strategy designed to test the integrity and flow characteristics of the EGR system. The monitor is activated during EGR system operation and after certain base engine conditions are satisfied. Input from the ECT, IAT, TP and CKP sensors is required to activate the EGR Monitor. Once activated, the EGR Monitor will perform each of the tests described below during the engine modes and conditions indicated. With the exception of Diagnostic Trouble Code (DTC) P0400, the EGR Monitor tests are also performed during on demand self-test.
The EGR Position sensor and circuit are continuously monitored for opens and shorts during closed throttle, low RPM conditions. Faults are set when the EGR Position sensor voltage exceeds either of the minimum or maximum allowable limits.
The DTCs associated with this test are DTCs P1400 and P1401.
The stuck EGR valve continuously monitors the difference between desired and actual EGR valve position. If this difference remains high for an extended period of time, the test fails.
The DTCs associated with this test are DTCs P1407 and P1408.
Once per drive cycle during a steady state highway cruise condition, the difference between normal and minimum EGR flow is tested. The EGR monitor measures the difference in manifold pressure between EGR fully open and fully closed. EGR flow failure is detected when this manifold pressure difference falls outside of the calibrated minimum and maximum values.
The DTC associated with this test is DTC P0400.
The MIL is activated after one of the above tests fail on two consecutive drive cycles.

Figure 10: EGR Monitor—Sonic (Probe)

Fuel System Monitor
The Fuel System Monitor is an on-board strategy designed to monitor the adaptive fuel control system. The fuel control system uses adaptive fuel tables stored in Keep Alive Memory (KAM) to compensate for variability in fuel system components due to normal wear and aging. During closed-loop vehicle operation, the adaptive fuel strategy learns the corrections needed to correct a "biased" rich or lean fuel system. The correction is stored in the adaptive tables. The fuel adaptive system has two means of adapting; a Long Term Fuel Trim (LONGFT) and a Short Term Fuel Trim (SHRTFT). LONGFT relies on the adaptive fuel tables and SHRTFT refers to the desired air/fuel ratio parameter "LAMBSE". Both are described in greater detail in this section in Powertrain Control Software, Adaptive Fuel Control Strategy under EEC-V Software. Input from the ECT, IAT, and MAF sensors is required to activate the adaptive fuel control system, which in turn activates the Fuel System Monitor. Once activated, the Fuel System Monitor looks for the adaptive tables to reach the adaptive clip and LAMBSE to exceed a calibrated limit. The Fuel System Monitor will store the appropriate DTC when a fault is detected as described below.
The Heated Oxygen Sensor (HO2S) detects the presence of oxygen in the exhaust and provides the PCM with feedback indicating air/fuel ratio.
A correction factor is added to the fuel injector pulsewidth calculation according to the Long and Short Term Fuel Trims as needed to compensate for variations in the fuel system.
When deviation in the parameter LAMBSE gets larger and larger air/fuel control suffers and emissions increase. When LAMBSE exceeds a calibrated limit and the adaptive fuel table has clipped, the Fuel System Monitor sets a Diagnostic Trouble Code (DTC) as follows:
The DTCs associated with the monitor detecting a lean shift in fuel system operation are DTCs P0171 and P0174.
The DTCs associated with the monitor detecting a rich shift in fuel system operation are DTCs P0172 and P0175.
The MIL is activated after a fault is detected on two consecutive drive cycles.

Figure 11: Fuel System Monitor

Heated Oxygen Sensor (HO2S) Monitor

The HO2S Monitor is an on-board strategy designed to monitor the HO2S sensors for a malfunction or deterioration which can affect emissions. The fuel control HO2S is checked for proper output voltage and response rate (the time it takes to switch from lean to rich and vice versa). The HO2S heater circuit is monitored by detecting proper voltage change as the heater is turned on and off. Downstream HO2S used for Catalyst Monitor are also monitored for proper output voltage. The illustration below shows that input is required from the ECT, IAT, MAF, and CKP sensors to activate the HO2S Monitor. The Fuel System Monitor and Misfire Monitor must also have completed successfully before the HO2S Monitor is enabled. Some of the HO2S Monitor checks are also performed during on demand self-test.
The HO2S sensor senses the oxygen content in the exhaust flow and outputs a voltage between zero and 1.0 volt. Lean of stoichiometric (air/fuel ratio of approximately 14.7:1), the HO2S will generate a voltage between zero and 0.4 volts. Rich of stoichiometric, the HO2S will generate a voltage between 0.5 and 1.0 volt. The HO2S Monitor evaluates both the upstream (fuel control) and downstream (Catalyst Monitor) HO2S for proper function.
Once the HO2S Monitor is enabled, the upstream HO2S signal voltage amplitude and response frequency are checked. Excessive voltage is determined by comparing the HO2S signal voltage to a maximum calibratable threshold voltage. A fixed frequency closed loop fuel control routine is executed and the upstream HO2S voltage amplitude and output response frequency are observed. A sample of the upstream HO2S signal is evaluated to determine if the sensor is capable of switching or has a slow response rate. A HO2S heater circuit fault is determined by turning the heater on and off and looking for a corresponding change in the Output State Monitor (OSM) and by measuring the current going through the heater circuit. The HO2S Monitor DTCs can be categorized as follows:
The DTCs associated with HO2S lack of switching are DTCs P1130, P1131, P1132, P1150, P1151 and P1152.
The DTCs associated with HO2S slow response rate are DTCs P0133 and P0153.
The DTCs associated with HO2S signal circuit malfunction are DTCs P0131, P0136, P0151 and P0156.
The DTCs associated with a HO2S heater circuit malfunction are DTCs P0135, P0141, P0155 and P0161.
The DTC associated with the downstream HO2S not running in on-demand is DTC P1127.
The DTCs associated with swapped HO2S connectors are DTCs P1128 and P1129.
The MIL is activated after a fault is detected on two consecutive drive cycles.

 

Thanks for the feedback, have the EGR and its control solenoid located, was wondering if the 96 5.0 vintage had the DPFE sensor as does our 4.2L has. Changing subject, how is yours running? Seem to recall you have one of them also. Mine is going great, can't think of a more pleasurable vehicle to drive except perhaps my 69 390 LTD 4 Dr cruiser.

 

 

It's been running good. I ran some sea foam thru it about two weeks ago and it felt like it was new again. It just seems to chug right along with no problems.

 

WOW, holy cow, golly gee, in the time it took me to respond to Darth Bama, my screen exploded with all this info. I thank you Dirtbuster 1. I will need an interpretor to help me with the info. . Actually it is more than I requested. Don't have a printer to copy it but I assure you, I will study it to my fullest capacity. I owe you, hopefully I can assist in the future.

 

If you need more info let me know!

 

Dirtbuster 1, as I cannot locate the DPFE sensor at this time for the 96 5.0 engine, am I wrong to use the following:


"The test for a stuck open EGR valve or EGR flow at idle is continuously performed whenever at idle (TP sensor indicating closed throttle). The monitor compares the DPFE circuit voltage at idle to the DPFE circuit voltage stored during key on engine off to determine if EGR flow is present at idle.
The DTC associated with this test is DTC P0402."


Couldn't my EGR be just sticking causing the code.

Your thoughts are welcomed.

 

That's exactly what I think it is. I had the same thing happen to me on my 2002. I also opted to change the DPFE sensor a day later. Knock on wood, never seen code again. It's been about 2 years ago and no problems.