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Home >> Mazda >> 1999 >> B2500 SX, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 4 (Engine Controls - Self-Diagnostics - EEC-V - 6.8L (99S E Series & 99S F350 To F550)) >> System Tests >> Test Dd: Fuel Rail Pressure (FRP) Sensor >> Diagnostic Aids

Diagnostic Aids

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Perform this test when directed by QUICK TEST. This test is intended to diagnose the following:

FRP SENSOR VOLTAGE-TO-FUEL PRESSURE CONVERSION

Volts Pressure (psi)
Natural Gas Vehicles
4.5 150
4.1 140
3.7 130
3.3 120
2.9 110
2.5 100
2.1 90
1.7 80
1.3 70
0.9 60
0.5 50
0.1 40
0.0 37.5
Except Natural Gas Vehicles
4.5 70
3.9 60
3.4 50
2.8 40
2.2 30
1.6 20
1.1 10
0.5 Zero

  1. 1) DTC P0192

    This DTC indicates FRP voltage signal is less than self-test minimum. Possible causes for this fault are:
    • FRP signal is shorted to SIG RTN or PWR GND.
    • FRP circuit is open.
    • Low fuel pressure.
    • Faulty FRP sensor.
    • Faulty PCM.

    Ensure vehicle has fuel (Natural Gas vehicles). Turn ignition on. Using scan tool, access FRP PID from PID/DATA monitor menu. If PID voltage is less than .2 volt, go to next step (Natural Gas vehicles) or step  3) (all other models). If PID voltage is .2 volt or more, go to step  13).

  2. 2) Check Fuel Pressure (Natural Gas Vehicles)

    Install fuel pressure gauge. Start engine and observe fuel pressure. If fuel pressure is more than 50 psi (345 kPa), go to next step. If fuel pressure is 50 psi (345 kPa) or less, go to TEST HB .
    NOTE: Fuel Rail Pressure (FRP) sensor may also be known as Injection Pressure (IP) sensor.

  3. 3) Generate Opposite Signal

    Turn ignition off. Disconnect FRP sensor connector. On Natural Gas vehicles, connect a jumper wire between FRP terminal and VREF terminal at FRP sensor wiring harness connector. On all models, if scan tool communication problem is present, disconnect jumper wire and go to step  24). Using scan tool, select FRP V PID from PID/DATA monitor menu. If PID voltage is 4.6 volts or less, disconnect jumper wire and go to next step. If PID voltage is more than 4.6 volts, replace FRP sensor.

  4. 4) Measure VREF Voltage

    With FRP sensor disconnected, turn ignition on. Measure voltage between VREF terminal and SIG RTN terminal at FRP sensor wiring harness connector. See Fig 1 or Fig 2 . If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, reconnect sensor and go to TEST C .
    Fig 1: Identifying Fuel Rail Pressure (FRP) Sensor Circuits & Connector Terminals (Natural Gas Vehicles)
    G99D02086Courtesy of FORD MOTOR CO.
    Fig 2: Identifying Fuel Rail Pressure (FRP) Sensor Circuits & Connector Terminals (All Other Models)
    G99J02112Courtesy of FORD MOTOR CO.

  5. 5) Check FRP Circuit Resistance

    Turn ignition off. Leave FRP sensor disconnected. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between FRP terminal at FRP sensor wiring harness connector and PCM connector pin No. 63. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in VPWR circuit.

  6. 6) Check FRP Circuit For Short To PWR GND Or SIG RTN

    Measure resistance between PCM connector pins No. 63 and No. 91 (SIG RTN). Also measure resistance between ground and PCM connector pin No. 63. If any resistance reading is 10,000 ohms or less, repair short circuit. If both resistance readings are more than 10,000 ohms, replace PCM.

  7. 7) DTC P0193

    This DTC indicates FRP voltage signal is more than self-test maximum. Possible causes for this fault are:
    • FRP signal is shorted to VREF or PWR.
    • High fuel pressure.
    • Faulty FRP sensor.
    • Faulty PCM.

    Turn ignition on. Using scan tool, select FRP V sensor from PID/DATA monitor menu. On Natural Gas vehicles, if PID voltage is more than 4.5 volts, go to step  9). On all other models, if PID voltage is more than 4.8 volts, go to next step. On all models, if PID voltage is not as specified, fault may be intermittent. Go to step  14).

  8. 8) Check Fuel Rail Pressure (FRP) Sensor For Leaks

    Remove vacuum hose from FRP sensor. Inspect sensor and vacuum hose for fuel. If any fuel is present, replace FRP sensor. If no fuel is present, go to step  10).

  9. 9) Check Fuel Pressure (Natural Gas Vehicles)

    Install fuel pressure gauge. Start engine and observe fuel pressure. If fuel pressure is more than 150 psi (1034 kPa), go to TEST HB . If fuel pressure is 150 psi (1034 kPa) or less, go to next step.

  10. 10) DTC P0193: Generate Opposite Signal

    Turn ignition off. Disconnect FRP sensor connector. Connect a jumper wire between FRP and SIG RTN terminals at FRP sensor connector. Turn ignition on. Using scan tool, select FRP V PID from PID/DATA monitor menu. If scan tool communication problem is present, disconnect jumper wire and go to step  24). If PID voltage is less than .2 volt, replace FRP sensor. If PID voltage is .2 volt or more, go to step  12).

  11. 11) DTC P0190

    Possible causes for this fault are:
    • VREF open circuit.
    • VREF open is sensor.

    Disconnect FRP sensor connector. Turn ignition on. Measure voltage between VREF and SIG RTN terminals at FRP sensor wiring harness connector. If voltage is 4-6 volts, go to step  13). If voltage is not 4-6 volts, go to next step.

  12. 12) Check For Open Circuit

    Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 63 and FRP terminal at FRP sensor connector. Measure resistance between PCM connector pin No. 90 and VREF terminal at FRP sensor connector. Measure resistance between PCM connector pin No. 91 and SIG RTN terminal at FRP sensor connector. If all resistance readings are less than 5 ohms, go to next step. If any resistance reading is 5 ohms or more, repair open circuit.

  13. 13) Measure FRP Sensor Resistance

    Measure resistance between FRP and SIG RTN terminals at FRP sensor. Also measure resistance between FRP and VREF terminals at FRP sensor. If any resistance is not 30-40 k/ohms, replace FRP sensor. If both resistance readings are 30-40 k/ohms, proceed as follows:
    • If Continuous Memory DTC P0190 is present, go to step  15).
    • If DTC P0192 is present, replace PCM.
    • If DTC P0193 is present, go to next step.

  14. 14) Check FRP Circuit For Short To VREF Or VPWR

    Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 63 and pin No. 90 (VREF) and VPWR circuit pin at PCM. For PCM VPWR pin identification, see PCM VPWR PIN IDENTIFICATION  table. If both resistance readings are more than 10,000 ohms, replace PCM. If any resistance reading is 10,000 ohms or less, repair short circuit.
    PCM VPWR TERMINAL IDENTIFICATION

    Application PCM Terminal No.
    Contour 2.0L A/T, Cougar 2.0L A/T & Mystique 2.0L A/T 97
    All Other Models 71

  15. 15) Check For Intermittent Fault

    Reconnect FRP sensor connector. Turn ignition on. Using scan tool, select FRP V PID from PID/DATA monitor menu. Observe PID voltage for fault while tapping on FRP sensor. Wiggle and bend wiring harness and connector between sensor and PCM. Fault will be indicated by a sudden change in PID voltage. If fault is indicated, isolate and repair as necessary. If fault is not indicated, symptom is intermittent and cannot be located at this time. Go to TEST Z  for additional test procedures.

  16. 16) KOEO/KOER DTC P0191

    DTC P0191 indicates FRP voltage signal is more than self-test maximum. Possible causes for this fault are:
    • High fuel pressure.
    • Low fuel pressure.
    • Excessive resistance in circuit.
    • Faulty FRP sensor.
    • Low or no fuel.

    Turn ignition on. Ensure vehicle has fuel. Turn ignition off. Release fuel pressure. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Connect pressure gauge to Schrader valve. With engine running, check fuel pressure. If fuel pressure is 80-120 (552-827 kPa) on Natural Gas vehicles or 20-60 psi (138-413 kPa) on all other models, go to next step. If fuel pressure is not as specified, go to TEST HB  (Natural Gas vehicles) or TEST HC  (all other models) .

  17. 17) Check FRP PID Fuel Pressure

    Turn ignition on. Using scan tool, select FRP PID from PID/DATA monitor menu. If PID psi reading is not within 10 psi of fuel pressure gauge psi reading in step  16), go to next step (Natural Gas vehicles) or step  18) (all other models). If PID psi reading is within 10 psi, proceed as follows:
    • If DTC P1168 or DTC P1169 is not present, repeat QUICK TEST .
    • If DTC P1168 or DTC P1169 is present, clear DTCs. Road test vehicle 3-5 minutes at a steady speed. Stop vehicle and check for Continuous Memory DTCs. If DTC P1168 or DTC P1169 is present, go to next step.

  18. 18) Check Fuel Rail Solenoid

    Using scan tool, access OUTPUT TEST MODE. While observing fuel rail solenoid, cycle output on and off several times. If solenoid clicking can be heard or felt, exit output test mode and go to next step. If no solenoid clicking can be heard or felt, go to step  22).

  19. 19) Measure VREF Voltage

    Disconnect FRP sensor connector. Turn ignition on. Measure voltage between VREF terminal and SIG RTN terminal at FRP sensor wiring harness connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, reconnect sensor and go to TEST C .

  20. 20) Check FRP Circuit For Excessive Resistance

    Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between FRP terminal at FRP sensor wiring harness connector and PCM connector pin No. 63. Measure resistance between SIG RTN terminal at FRP sensor wiring harness connector and PCM connector pin No. 91 (SIG RTN). Also measure resistance between VREF terminal at FRP sensor wiring harness connector and PCM connector pin No. 90. If all resistance readings are less than 5 ohms, go to next step. If any resistance reading is 5 ohms or more, repair circuit.

  21. 21) Monitor FRP Circuit With Scan Tool

    Turn ignition on. Using scan tool, select FRP V PID from PID/DATA monitor menu. If PID voltage is less than .2 volt (Natural Gas vehicles) or more than 4.8 volts (all other models), replace FRP sensor. If PID voltage is not as specified, replace PCM.

  22. 22) Check Voltage At Fuel Rail Solenoid

    Using scan tool, access OUTPUT TEST MODE. Turn all outputs on. Disconnect fuel rail solenoid connector. Measure voltage between VPWR circuit terminal (Pink/Black wire) at fuel rail solenoid wiring harness connector and negative battery terminal. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, repair open in VPWR circuit.
    NOTE: When in output test mode, voltage measurement must be made within 7 seconds of activating test mode.

  23. 23) Check Ground Circuit

    Using scan tool, access OUTPUT TEST MODE. Turn all outputs on. Measure voltage between VPWR (Pink/Black wire) and ground circuit terminals at fuel rail solenoid wiring harness connector and negative battery terminal. If voltage is more than 10.5 volts, replace fuel rail solenoid. If voltage is 10.5 volts or less, repair open circuit.

  24. 24) Check VREF Voltage To FRP Sensor

    Disconnect FRP sensor connector. Turn ignition on. Measure voltage between VREF and SIG RTN circuit terminals at FRP sensor wiring harness connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, VREF is out of range. Go to TEST C .

  25. 25) Check For Shorted FRP Signal

    Turn ignition off. Disconnect scan tool Data Link Connector (DLC). Disconnect PCM 104-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Measure resistance between PCM connector pin No. 63 and pins No. 90 and 91. Also measure resistance between PCM connector pin No. 63 at and negative battery terminal. If all resistance readings are more than 10,000 ohms, replace PCM. If any resistance reading is 10,000 ohms or less, repair short circuit.
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