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  • PCM commanded EVR to open EGR EGR poppet (pintle) is open Exhaust flows into the inlet (intake) manifold DPFE sensor is sampling gas flow and returning a reading to the PCM PCM varies opening of EGR while making adjustments to ignition timing OBD2 actually reads volume of gas entering intake for precise timing adjustments The EGR tube restriction (orifice) causes a venturi effect Sample pressure from each side of the orifice is sent to the DPFE
  • Differential Pressure Feedback EGR Sensor A Ceramic, capacitive type pressure transducer. Voltage signal to PCM is proportionate to pressure drop across an orifice in EGR pipe. PCM accurately determines gas flow through the tube. Two different sensors are in use, one metal and the other plastic. (not interchangeable)
  • Hose Test Next, the DPFE Monitor will check the integrity of the DPFE signal hoses. The test is run during a period of acceleration, when the PCM commands the EGR valve to close momentarily, and then checks the DPFE signal for a voltage consistent with zero flow. A voltage increase or decrease during acceleration indicates a fault with the hoses during this test. This will generate the following DTCs,  P1405 DPFE sensor Upstream hose off or plugged P1406 DPFE sensor Downstream hose off or plugged . NOTE: plugged in this context means blocked. This could either be an intentional plugging, blockage by foreign matter, kinking or melting which stops the gas flow. It is not difficult for work on the engine to knock off a sensor pipe either.  Not all applications use the P1406 code . In these vehicles the error code P1401 is recorded instead.
  • Flow Checks Now the system checks the EGR for correct gas flow. During steady state driving with moderate loads and engine speeds the EVR duty cycle (operating rate) will keep increasing until the sufficient flow rate is produced. If the EVR duty cycle reaches 80% (ie 80% open) the PCM checks the DPFE sensor voltage with a table in memory to check that the gas flow is within parameters. If the voltage is too high it indicates that there is insufficient gas flow, and this stores the DTCs P1401 EGR Insufficient Gas FLow detected . P1408 EGR Flow out of self-test Range . (This is a KOER self test, rather than a n EGR Monitor code.) This is a functional test and will record a DTC for any flow restriction or incorrect DPFE signal Note: P0401 may also be generated for a hose off error, or if the DPFE sensor is failing because its voltage will not match the expected response stored in the PCM. An open in the VREF wire also causes a P0401 since the voltage does not match the expected response.
  • Ford DPFE

    1. 1. The Whole System
    2. 2. The Whole System
    3. 3. Ford DPFE EGR System
    4. 4. 2. Pintle opens 1 . vacuum applied 3. EXHAUST GAS FLOWS No Electronics at the Valve
    5. 5. <ul><li>Ford DPFE </li></ul><ul><li>Differential (Delta) Pressure Feedback EGR Sensor </li></ul><ul><li>Detects EGR Flow </li></ul>Note Tube connections “REF” Valve closed Valve open
    6. 6. DPFE Basic Schematic and Sensor Data
    7. 7. EGR Vacuum Regulator (EVR) <ul><li>EVR Regulates vacuum to EGR </li></ul><ul><li>Controlled by PWM to open and close EGR valve. </li></ul><ul><li>As duty cycle increases, EVR increases vacuum to EGR. </li></ul><ul><li>EGR opens at about 40% duty cycle. </li></ul><ul><li>Note “filter” is where vacuum bleeds </li></ul>
    8. 8. EGR Vacuum Regulator (EVR) Normally Bleeds about 1”Hg of Vacuum With Solenoid at 100% duty should output about 7”Hg Vent through filter cap
    9. 9. Basic EVR Schematic & Spec VPWR = Battery voltage
    10. 10. ORIFICE TUBE Tube feeds exhaust gas to EGR valve Requires no maintenance DPFE measures pressure drop across metering orifice
    11. 11. Ford DPFE EGR System Diagnostics <ul><li>KOEO self-test: Checks for DPFE sensor out of expected range (Pass codes here indicate DPFE & EVR circuits are in expected range </li></ul><ul><li>Continuous Memory : Stores any intermittent faults </li></ul><ul><li>KOER self-test: Functional test of DPFE, EGR Valve, and EVR (Pass codes here indicate EGR system OK) </li></ul><ul><li>DPFE Scan DATA .55V to 1V with valve closed </li></ul>
    12. 12. KOEO Circuit Checks DPFE sensor is tested for out of range values (typically >4.96 volts, <0.195 volts) and if this is detected the DTC P1400 or P1401 is set. EVR Output circuit is checked for opens and short using the internal smart driver in the PCM, and a failure records P1409 .
    13. 13. <ul><li>KOER Idle Valve Stuck Open Test </li></ul><ul><li>PCM checks DPFE voltage and compares it with last KOEO DPFE voltage state </li></ul><ul><li>If voltage is different this indicates a exhaust gas flow is present at idle </li></ul><ul><li>PCM stores DTC P0402 EGR Flow Excessive Gas Detected </li></ul><ul><li>(EGR poppet (pintle) valve has stuck open (false DTC sets if tube leaks) </li></ul>
    14. 14. <ul><li>KOER Hose Test </li></ul><ul><ul><li>During acceleration (or KOER test), PCM commands EGR closed </li></ul></ul><ul><ul><li>PCM checks DPFE signal for a voltage consistent with zero flow </li></ul></ul><ul><ul><li>A DPFE voltage difference during acceleration with EGR shut indicates a hose fault </li></ul></ul><ul><ul><li>P1405 DPFE sensor Upstream hose off or plugged </li></ul></ul><ul><ul><li>P1406 (or P1401) DPFE sensor Downstream hose off or plugged . </li></ul></ul>
    15. 15. <ul><li>Functional Flow Checks (gas restriction or DPFE signal incorrect) </li></ul><ul><li>Cruise speeds, PCM checks EVR duty verses DPFE sensor voltage </li></ul><ul><li>If EVR duty is too high, there is insufficient gas flow </li></ul><ul><li>P1401 EGR Insufficient Gas FLow detected (with EVR above 80%) </li></ul><ul><li>(1401 also: possible sensor, open in VREF or down steam hose off) </li></ul><ul><li>P1408 EGR Flow out of self-test Range (KOER self test, not Monitor) </li></ul>