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Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Mazda B4000, 2002 Mazda B3000, and 2002 Mazda B2300. However, it is still accessible from the selected car via links, so may be relevant.
  1. If QUICK TEST was not performed, go to QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If QUICK TEST was performed:
    • For DTC P1400, go to step  2 .
    • For DTC P1401, go to step  6 .

  2. DTC P1400: Verify Differential Pressure Feedback EGR (DPFEGR) Voltage

    With KOEO, using scan tool, select Diagnostic Data Link. Select PCM. Select PID/Data Monitor and Record. Access and observe DPFEGR PID. Turn ignition off. If DPFEGR PID voltage is less than 0.2 volts, DPFEGR sensor voltage is less than acceptable minimum. Go to next step. If DPFEGR PID voltage is 0.2 volts or more, fault is intermittent. Go to step  14 .

  3. Induce Opposite DPFEGR Sensor Voltage

    Disconnect DPFEGR sensor connector. With KOEO, using scan tool, select Diagnostic Data Link. Select PCM. Select PID/Data Monitor and Record. Access and observe DPFEGR PID. Turn ignition off. If DPFEGR PID is 4-6 volts, replace faulty DPFEGR sensor. Go to step  15 . If DPFEGR PID is not 4-6 volts, go to next step.

  4. Measure VREF Voltage At DPFEGR Sensor Vehicle Harness Connector

    With KOEO, measure voltage between VREF circuit (Brown/White wire) and SIG RTN circuit (Gray/Red wire) at DPFEGR sensor harness connector. See Fig 1 . Turn ignition off. If VREF voltage is 4-6 volts, go to next step. If VREF voltage is not 4-6 volts, VREF voltage is out of range. See VEHICLE REFERENCE VOLTAGE  under SYSTEM TESTS.
    Fig 1: Identifying DPFEGR Sensor Harness Connector Circuits
    G00155552Courtesy of MAZDA MOTORS CORP.

  5. Check DPFEGR Circuit For Shorts To Ground & SIG RTN

    Disconnect scan tool from DLC. Disconnect PCM connector. Install breakout box, leaving PCM disconnected. Measure resistance between breakout box terminals No. 65 (DPFEGR SIG circuit) and 91 (SIG RTN circuit). Record reading. Measure resistance between breakout box terminals No. 65 (DPFEGR SIG circuit) and 51 or 103 (SIG RTN circuit). Record reading. If each resistance reading is more than 10,000 ohms, replace faulty PCM. Go to step  15 . If either resistance reading is 10,000 ohms or less, repair short circuit. See WIRING DIAGRAMS article. Go to step  15 .

  6. DTC P1401: Verify DPFEGR PID Voltage

    With KOEO, using scan tool, access and observe DPFEGR PID. Turn ignition off. If DPFEGR PID voltage is more than 4 volts, DPFEGR sensor voltage is more than acceptable maximum. Go to next step. If DPFEGR PID voltage is 4 volts or less, fault is intermittent. Go to step  14 .

  7. Check DPFEGR SIG Circuit For Short To PWR

    Disconnect DPFEGR sensor harness connector. With KOEO, measure voltage between DPFEGR SIG circuit (Brown/Light Green wire) between DPFEGR sensor harness connector and battery negative terminal. Turn ignition off. If voltage is more than 10.5 volts, DPFEGR sensor voltage input is indicating a short to power. Go to next step. If voltage is 10.5 volts or less, go to step  9 .

  8. Check DPFEGR SIG Circuit For Short To PWR In Harness

    Disconnect PCM connector. Install breakout box, leaving PCM disconnected. With KOEO, measure voltage between breakout box terminals No. 65 (DPFEGR SIG circuit) and 103 (PWR GND circuit). Turn ignition off. If voltage is more than 10.5 volts, repair short circuit. See WIRING DIAGRAMS article. Go to step  15 . If voltage is 10.5 volts or less, replace faulty PCM. Go to step  15 .
    NOTE: During next test step, If a scan tool communication concern is present, immediately remove jumper wire. Go to step  14 .

  9. Induce Opposite DPFEGR Sensor Voltage

    Connect a jumper wire between DPFEGR SIG circuit (Brown/Light Green wire) and SIG RTN circuit (Gray/Red wire) at DPFEGR sensor harness connector. See Fig 1 . Using scan tool, select Diagnostic Data Link. Select PCM. Select PID/Data Monitor and Record. Access and observe DPFEGR PID. Turn ignition off. If DPFEGR PID voltage is less than 0.05 volt, remove jumper wire. Go to next step. If DPFEGR PID voltage is 0.05 volt or more, unable to induce opposite signal. Go to step  12 .

  10. Verify VREF Is In Range

    With KOEO, measure voltage between DPFEGR sensor connector VREF circuit (Brown/White wire) and SIG RTN circuit (Gray/Red wire). Turn ignition off. If VREF voltage is 4-6 volts, go to next step. If VREF voltage is not 4-6 volts, go to VEHICLE REFERENCE VOLTAGE  under SYSTEM TESTS.

  11. Check DPFEGR SIG For Short To VREF In Harness

    Turn ignition off. Disconnect PCM connector. Install breakout box, leaving PCM disconnected. Measure resistance between breakout box terminals No. 65 (DPFEGR SIG circuit) and 90 (VREF circuit). If resistance is more than 10,000 ohms, replace faulty DPFEGR sensor. Go to step  15 . If resistance is 10,000 ohms or less, repair short circuit. See WIRING DIAGRAMS article. Go to step  15 .

  12. Check DPFEGR SIG Circuit For Open In Harness

    Turn ignition off. Disconnect PCM connector. Install breakout box, leaving PCM disconnected. Measure resistance of DPFEGR SIG circuit (Brown/Light Green wire) between breakout box terminal No. 65 and DPFEGR sensor harness connector. See Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. See WIRING DIAGRAMS article. Go to step  15 .

  13. Check SIG RTN For Open In Harness

    Measure resistance of DPFEGR SIG RTN circuit (Brown/Light Green wire) between breakout box terminal No. 91 and DPFEGR sensor harness connector. If resistance is less than 5 ohms, replace faulty PCM. Go to step  15 . If resistance is 5 ohms or more, repair open circuit. See WIRING DIAGRAMS article. Go to step  15 .

  14. Wiggle Test DPFEGR Sensor & Harness

    With KOEO, using scan tool, select Diagnostic Data Link. Select PCM. Select PID/Data Monitor and Record. Access and observe DPFEGR PID. Lightly tap on DPFEGR sensor, wiggle DPFEGR sensor connector and vehicle harness between sensor and PCM. A fault is indicated by a sudden change in DPFEGR PID voltage. If a fault is indicated, isolate fault and repair as necessary. Go to next step. If a fault is not indicated, unable to duplicate or identify fault at this time. See INTERMITTENT  under SYSTEM TESTS.

  15. Verify Trouble Shooting Of DTCs Completed

    Reconnect all electrical connectors. Perform QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If same DTC is present, replace faulty PCM. Repeat QUICK TEST  under SELF-DIAGNOSTIC SYSTEM. If any other DTC is present, go to applicable procedure for other DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no DTCs are set, trouble shooting is complete.
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