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DTC 621: Fuel Tank Pressure Sensor Signal

  1. If fault is permanent, signal too high, go to next step. If fault is permanent, signal too low, go to step 7). If fault is permanent, signal sporadic, go to step 14). If fault is intermittent, signal too high, go tostep 18). If fault is intermittent, signal too low, go to step 19). If fault is intermittent, signal sporadic, go to step 20).
  2. Turn ignition off. Wait about 2 minutes. Disconnect fuel tank pressure sensor. Connect ohmmeter between fuel tank pressure sensor connector terminal No. 2 and ground. If ohmmeter reads about zero ohms, go to step 4). If ohmmeter does not read about zero ohms, go to next step.
  3. Ensure ignition is off and fuel tank pressure sensor is disconnected. Check all connectors and wiring between fuel tank pressure sensor and ECM for an open circuit or poor terminal contact. Connect ohmmeter between fuel tank pressure sensor connector terminal No. 2 and ground. If about zero ohms are present, problem was caused by poor terminal contact. If about zero ohms are not present, check wiring between fuel tank pressure sensor terminal No. 2 and ECM connector terminal A18 for an open circuit. Repair as necessary.
  4. Turn ignition on. Disconnect fuel tank pressure sensor connector. Measure voltage between fuel tank pressure sensor connector terminal No. 3 and ground. If voltage is less than 5 volts, go to next step. If voltage is greater than 6 volts, check all wiring and connectors between fuel tank pressure sensor and ECM for a short circuit to voltage. If voltage is 5-6 volts, go to step 6).
  5. Turn ignition off. Disconnect fuel tank pressure sensor connector. Check ECM and other connectors between fuel tank pressure sensor and ECM for an open circuit or poor terminal contact. Repair as necessary. Reconnect all connectors. Turn ignition on. Using voltmeter, backprobe between fuel tank pressure sensor connector terminal No. 3 and ground. If about 5 volts are present, system is okay. If about 5 volts are not present, repair open circuit in wiring between fuel tank pressure sensor and ECM terminal B31. See WIRING DIAGRAMS .
  6. Turn ignition off. Ensure fuel tank pressure sensor is connected. Start and idle engine for several minutes. Using scan tool, check DTC status message. If an alternative permanent fault is present, replace fuel tank pressure sensor. If alternative intermittent fault is present, DTC was caused by loose connection in fuel tank pressure sensor. Repair as necessary.
  7. If fault is permanent, signal too low, turn ignition off. Wait about 2 minutes. Disconnect fuel tank pressure sensor. Connect ohmmeter between fuel tank pressure sensor connector terminal No. 1 and ground. If ohmmeter reads about .2-1.5 k/ohms, go to step 13). If ohmmeter reads less than .2 k/ohms, go to next step. If ohmmeter reads greater than 1.5 k/ohms, go to step 12).
  8. Ensure ignition is off. Disconnect fuel tank pressure sensor. Disconnect accelerometer. Connect ohmmeter between fuel tank pressure sensor connector terminal No. 1 and ground. If ohmmeter reads about .2-1.5 k/ohms, replace accelerometer. If ohmmeter does not read about .2-1.5 k/ohms, go to next step.
  9. Ensure ignition is off. Disconnect fuel tank pressure sensor, accelerometer, and A/C pressure sensor connectors. Connect ohmmeter between fuel tank pressure sensor connector terminal No. 1 and ground. If ohmmeter reads .2-1.5 k/ohms, replace A/C pressure sensor. If ohmmeter does not read .2-1.5 k/ohms, go to next step.
  10. Ensure ignition is off and fuel tank pressure sensor, accelerometer, A/C pressure sensor, and atmospheric pressure sensor connectors are disconnected. Connect ohmmeter between fuel tank pressure sensor connector terminal No. 3 and ground. If ohmmeter reads .2-1.5 k/ohms, replace atmospheric pressure sensor. If ohmmeter does not read .2-1.5 k/ohms, go to next step.
  11. Fuel tank pressure sensor power lead is connected inside ECM to accelerometer and A/C pressure sensor power leads. If a problem occurs in any power lead all 3 components will be affected. Check for an open circuit or short to ground in wiring between accelerometer terminal No. 1 and ECM terminal B1, A/C pressure sensor terminal No. 3 and ECM terminal B29, and fuel tank pressure sensor terminal No. 1 and ECM terminal B15. Repair as necessary.
  12. Ensure ignition is off. Disconnect fuel tank pressure sensor connector. Check ECM connector for poor terminal contact. Repair as necessary. Reconnect ECM connector. Connect ohmmeter between fuel tank pressure sensor connector terminal No. 1 and ground. If ohmmeter reads about .2-1.5 k/ohms, problem was caused by poor terminal contact. If ohmmeter does not read about .2-1.5 k/ohms, check wiring between fuel tank pressure sensor terminal No. 1 and ECM connector terminal B15 for an open circuit. Repair as necessary.
  13. Turn ignition off. Disconnect fuel tank pressure sensor. Turn ignition on. Connect voltmeter between fuel tank pressure sensor connector terminal No. 3 (ECM side) and ground. If voltmeter reads about 5-6 volts, replace fuel tank pressure sensor. If voltmeter does not read about 5-6 volts, check wiring between fuel tank pressure sensor terminal No. 3 and ECM connector B31 for an open circuit.
  14. If fault is permanent, signal sporadic, turn ignition off. Check fuel tank pressure sensor, ECM, and all other tank pressure sensor connectors for poor terminal contact. Repair as necessary. Read off DTCs. If DTC 621 is stored with intermittent fault status, DTC was caused by poor terminal contact. If DTC is stored with permanent status, go to next step.
  15. Check all fuel tank pressure sensor wiring and connectors for open circuits or poor terminal contact. If wiring and connectors are okay, note that fuel tank pressure sensor power lead is connected inside ECM to A/C pressure sensor and accelerometer power leads. If a problem occurs in any lead all 3 components will be affected. If DTC 621 continues to have permanent fault status, go to next step.
  16. Ensure ignition is off. Ensure fuel tank pressure sensor is connected. Disconnect A/C pressure sensor. Start and idle engine for 5 minutes. Read off DTCs. If DTC 621 is stored with intermittent fault status, replace A/C pressure sensor. If DTC 621 is stored with permanent fault status, go to next step.
  17. Reconnect A/C pressure sensor connector. Disconnect accelerometer connector. Start and idle engine for 5 minutes. Read off DTCs. If DTC 621 is stored with intermittent fault status, replace accelerometer. If DTC 621 is stored with permanent fault status, replace fuel tank pressure sensor.
  18. If fault is intermittent, signal too high, check fuel tank pressure sensor and ECM connectors for poor terminal contact. Check wiring between fuel tank pressure sensor connector terminal No. 3 and ECM terminal B31 for an intermittent open circuit or short circuit to voltage. Also check wiring between fuel tank pressure sensor terminal No. 2 and ECM terminal A18 for an intermittent open circuit. Repair as necessary.
  19. If fault is intermittent, signal too low, check fuel tank pressure sensor and ECM connectors for poor terminal contact. Repair as necessary. If terminal contact is okay, check for an intermittent short circuit to ground in wiring between fuel tank pressure sensor terminal No. 3 and ECM terminal B31, between fuel tank pressure sensor terminal No. 1 and ECM terminal B15, between accelerometer terminal No. 1 and ECM terminal B1, and between A/C pressure sensor terminal No. 3 and ECM terminal B29. Repair as necessary.
  20. If fault is intermittent, signal sporadic, check fuel tank pressure sensor and ECM connectors for poor terminal contact. Repair as necessary. If terminal contact is okay, check for an intermittent open circuit, or short circuit to ground or voltage in wiring between fuel tank pressure sensor terminal No. 1 and ECM terminal B15, between fuel tank pressure sensor terminal No. 3 and ECM terminal B31, and between fuel tank pressure sensor terminal No. 2 and ECM terminal A18. Repair as necessary.
  21. If wiring is okay, note that fuel tank pressure sensor power lead is connected inside ECM to A/C pressure sensor and accelerometer power leads. If anything happens to any of these power leads all 3 components will be affected. Check for an intermittent short circuit to voltage or ground in wiring between A/C pressure sensor terminal No. 3 and ECM terminal B29, and between accelerometer terminal No. 1 and ECM terminal B1.
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