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DTC 251: Outside Temperature Sensor Signal

  1. Check for additional DTCs. If DTCs 123 and 411 are present, go to next step. If DTCs 314 and 411 are not present, go to step 4).
  2. Check common outside temperature sensor and Throttle Position (TP) sensor terminal A18 on ECM for poor terminal contact. Repair as necessary, then go to next step.
  3. Turn ignition off. Reconnect electrical connectors and reinstall components. Turn ignition on. Using scan tool, read off outside temperature. If temperature value is within specification, system is okay. If temperature value is not within specification, no fault is present.
  4. If status message reads PERMANENT FAULT, SIGNAL TOO HIGH, go to next step. If status message reads PERMANENT FAULT, SIGNAL TOO LOW, go to step 11). If status message reads PERMANENT FAULT, FAULTY SIGNAL, go to step 12). If status message reads INTERMITTENT FAULT, SIGNAL TOO HIGH or INTERMITTENT FAULT, SIGNAL SPORADIC, go to step 14). If status message reads INTERMITTENT FAULT, SIGNAL TOO LOW, check wiring between outside temperature sensor terminal No. 1 and ECM terminal A35 for an intermittent short circuit. Repair as necessary.
  5. Turn ignition off. Wait about 2 minutes. Disconnect right outside temperature sensor located in air intake, below grille. Connect ohmmeter between outside temperature sensor connector terminal No. 2 and ground. If ohmmeter reads about zero ohms, go to next step. If ohmmeter does not read about zero ohms, go to step 7).
  6. Turn ignition on. Disconnect temperature sensor. Connect voltmeter between temperature sensor connector terminals No. 1 and 2 (ECM side). If voltmeter reads about 5 volts, go to step 8). If voltmeter reads less than 5 volts, go to step 10). If voltmeter reads greater than 5 volts, check wiring between outside temperature sensor terminal No. 1 and ECM terminal A35 for a short to voltage. Repair as necessary, then go to step 9).
  7. Turn ignition off. Disconnect outside temperature sensor connector. Check ECM connector for poor terminal contact. Repair as necessary. Reconnect ECM. Connect ohmmeter between temperature sensor connector terminal No. 2 (ECM side) and ground. If ohmmeter reads about zero ohms, DTC was caused by poor terminal contact at ECM connector. If ohmmeter does not read about zero ohms, check wiring between outside temperature sensor terminal No. 2 and ECM terminal A18 for an open circuit. Repair as necessary.
  8. Turn ignition off. Disconnect outside temperature sensor connector. Connect ohmmeter between outside temperature sensor terminals No. 1 and 2. If ohmmeter reads about 500 ohms at 77°F (25°C), DTC was caused by poor terminal contact at ECM connector. If ohmmeter does not read about 500 ohms at 77°F (25°C), replace outside temperature sensor.
  9. Turn ignition off. Disconnect outside temperature sensor connector. Connect ohmmeter between outside temperature sensor terminals No. 1 and 2. If ohmmeter reads about 500 ohms at 77°F (25°C), temperature sensor is okay. If ohmmeter does not read about 500 ohms at 77°F (25°C), replace outside temperature sensor.
  10. Turn ignition off. Disconnect outside temperature sensor connector. Check ECM connector for poor terminal contact. Repair as necessary. Reconnect ECM. Turn ignition on. Connect voltmeter between temperature sensor connector terminals No. 1 and 2 (ECM side). If voltmeter reads about 5 volts, DTC was caused by poor terminal contact at ECM connector. If voltmeter does not read about 5 volts, check wiring between outside temperature sensor terminal No. 1 and ECM terminal A35 for a short circuit to voltage.
  11. Turn ignition on. Disconnect right outside temperature sensor located in air intake, below grille. Connect voltmeter between outside temperature sensor connector terminal No. 1 and ground. If voltmeter reads about 5 volts, replace outside temperature sensor. If voltmeter does not read about 5 volts, check wiring between outside temperature sensor terminal No. 1 and ECM terminal A35 for a short to ground. Repair as necessary.
  12. Turn ignition off. Check outside temperature sensor and ECM connectors for poor terminal contact. Repair as necessary. Reconnect connectors. Start and idle engine. Wait about 5 minutes. Using scan tool, read off DTCs. If DTC is still stored with intermittent status, DTC was caused by poor terminal contact at outside temperature sensor and ECM connectors. If DTC is not stored with intermittent status, go to next step.
  13. Turn ignition off. Check outside temperature sensor and ECM connectors for poor terminal contact. Check wiring between outside temperature sensor connector terminal No. 1 and ECM terminal A35 for an intermittent open circuit. Also check wiring between outside temperature sensor connector terminal No. 2 and ECM terminal A18 for an intermittent open circuit. Repair as necessary. Reconnect connectors. Start and idle engine. Wait about 5 minutes. If DTC is stored with intermittent status, system is okay. If DTC is not stored with intermittent status, replace outside temperature sensor.
  14. Check outside temperature sensor and ECM connectors for poor terminal contact. Check wiring between outside temperature sensor connector terminal No. 1 and ECM terminal A35 for an intermittent open circuit. Also check wiring between outside temperature sensor connector terminal No. 2 and ECM terminal A18 for an intermittent open circuit. Repair as necessary.
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