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Home >> Volvo >> 1998 >> V70 GLT >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Tests >> DTC P0450/EFI 621, DTC P0451/EFI 621, DTC P0452/EFI 621 & DTC P0453/EFI 621 >> Diagnosis (Signal Too Low)

Diagnosis (Signal Too Low)

  1. Connect scan tool. See RETRIEVING & ERASING DTCs  under SELF-DIAGNOSTIC SYSTEM. If signal is PERMANENT, go to next step. If signal is INTERMITTENT, check the following:
    • Loose connections at fuel tank pressure sensor.
    • Loose connections at ECM harness connectors.
    • Loose connections at bulkhead connectors 24/2 and 24/4.
    • Intermittent short in circuit between fuel tank pressure sensor terminal No. 2 and ECM terminal B31 via bulkhead connector 24/2 terminal E5.
    • Intermittent short in bulkhead connector 24/2 terminal C6 circuit.
    • Intermittent short in circuit between tank pressure sensor terminal No. 3 and ECM terminal B15 via bulkhead connector 24/4 terminal E4.
    • Intermittent short in bulkhead connector 24/2 terminal C5 circuit.
    • Intermittent short to ground in circuit between accelerometer terminal No. 1 and ECM terminal B1.
    • Intermittent short to ground in circuit between A/C pressure sensor terminal No. 3 and ECM terminal B29.
    Repair as necessary. After repairs, go to step  10.
  2. Turn ignition off. Wait approximately 2 minutes. Disconnect fuel tank pressure sensor. Using DVOM, measure resistance between ground and fuel tank pressure sensor harness connector terminal No. 3. Resistance should be approximately 0.2-1.5 k/ohms. If resistance is as specified, go to step  7. If resistance is less than specified, go to next step. If resistance is more than specified, go to step  8.
  3. Turn ignition off. Disconnect accelerometer. Accelerometer is located in front of engine compartment. See Figure. Using DVOM, measure resistance between ground and fuel tank pressure sensor connector terminal No. 3. Resistance should be approximately 0.2-1.5 k/ohms. If resistance is as specified, replace accelerometer. After repairs, go to step  10. If resistance is not as specified, go to next step.
  4. Turn ignition off. Disconnect fuel tank pressure sensor, accelerometer and A/C pressure sensor harness connectors. Using DVOM, measure resistance between ground and fuel tank pressure sensor connector terminal No. 3. Resistance should be 0.2-1.5 k/ohms. If resistance is as specified, replace A/C pressure sensor. If resistance is not as specified, go to next step.
  5. Turn ignition off. Disconnect atmospheric pressure sensor harness connector. Atmospheric pressure sensor is located at left side of front engine compartment. See Figure. Using DVOM, measure resistance between ground and fuel tank pressure sensor connector terminal No. 3. Resistance should be 0.2-1.5 k/ohms. If resistance is as specified, replace atmospheric pressure sensor. If resistance is not as specified, go to next step.
  6. Fuel tank pressure sensor power supply is common to accelerometer and A/C pressure sensor. If a problem occurs in power supply, all 3 components will be affected. Check for an open circuit, or short to ground in circuits between following:
    • Accelerometer Terminal No. 1 And ECM Terminal B1
    • A/C Pressure Sensor Terminal No. 3 And ECM Terminal B29
    • Fuel Tank Pressure Sensor Terminal No. 3 And ECM Terminal B15
    Repair as necessary. After repairs, go to step  10.
  7. Turn ignition off. Disconnect fuel tank pressure sensor harness connector. Fuel tank pressure sensor is located on top of fuel tank. See Figure. Using DVOM, measure voltage between ground and fuel tank pressure sensor harness connector terminal No. 2. Voltage should be 5-6 volts. If voltage is within specification, replace fuel tank pressure sensor. After repairs, go to step  10. If voltage is not within specification, check for an open in signal circuit between fuel tank pressure sensor terminal No. 2 and ECM B31. Repair as necessary. After repairs, go to step  10.
  8. Turn ignition off. Check ECM harness connector and bulkhead connectors 24/2 and 24/4 for contact resistance and oxidation. Repair as necessary. Ensure ECM is securely connected. Ensure bulkhead connectors 24/2 and 24/4 are connected. Using DVOM, measure resistance between ground and fuel tank pressure sensor connector terminal No. 3. Resistance should be 0.2-1.5 k/ohms. If resistance is not within specification, go to next step. If resistance is within specification, system is okay. Go to step  10.
  9. Check for an open in circuit between fuel tank pressure sensor terminal No. 3 and ECM terminal B15. See Figure. Repair as necessary. After repairs, go to step  10.
  10. Turn ignition off. Reconnect all components. Start engine and idle. Using scan tool, read DTCs. If DTC P0452/EFI 621 is stored, DTC should have intermittent status. If signal is intermittent, fault was corrected. If signal is not intermittent, fault was not found. Repeat testing, starting with step  1.
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