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DTC 212: Front Ho2S Signal

  1. If fault is permanent and signal is too high, go to next step. If fault is permanent and signal is too low, go to step 5). If fault is permanent and signal is faulty, go to step 8). If fault is permanent and signal is missing, go to step 9). If fault is intermittent and signal is too low, go to step 12). If fault is intermittent and signal is faulty, go to step 13). If fault is intermittent and signal is missing, go to step 14). If fault is intermittent and signal is too high, go to step 15).
  2. Connect Breakout Box (981-3190) to ECM. Turn ignition on. Connect voltmeter between breakout box pins No. 33 and 42. If voltmeter reads about .7 volt, go to next step. If voltmeter does not read about .7 volt, disconnect front HO2S connector. Turn ignition on. Recheck voltage between breakout box pins. If voltmeter reads about .7 volt, install new front HO2S. If voltmeter does not read about .7 volt, disconnect front and rear HO2S connectors and repeat test. If voltmeter reads about .7 volt, install new rear HO2S. If voltmeter does not read about .7 volt, check wiring between front HO2S terminal No. 3 and ECM connector terminal A33, and wiring between rear HO2S terminal No. 3 and ECM connector terminal A19 for a short to ground.
  3. Turn ignition on. Connect voltmeter between breakout box pins No. 32 and 42. If voltage is about 1.2 volts, go to next step. If voltage is not about 1.2 volts, turn ignition off. Disconnect front HO2S connector. Repeat test. If voltage is now about 1.2 volts, replace front HO2S. If voltage is not about 1.2 volts, check wiring between front HO2S terminal No. 4 and ECM connector terminal A32 for a short to voltage.
  4. Turn ignition off. Disconnect rear HO2S connector. Connect voltmeter between breakout box pins No. 34 and 42. If voltage is now about 1.2 volts, replace rear HO2S. If voltage is not about 1.2 volts, check wiring between rear HO2S terminal No. 4 and ECM connector terminal A34 for a short to voltage.
  5. Connect Breakout Box (981-3190) to ECM. Turn ignition on. Connect voltmeter between breakout box pins No. 33 and 42. If voltmeter reads about .7 volt, go to next step. If voltmeter does not read about .7 volt, disconnect front HO2S connector. Turn ignition on. Recheck voltage between breakout box pins. If voltmeter reads about .7 volt, install new front HO2S. If voltmeter does not read about .7 volt, disconnect rear HO2S and repeat test. If voltmeter reads about .7 volt, install new rear HO2S. If voltmeter does not read about .7 volt, check wiring between front HO2S terminal No. 3 and ECM connector terminal A33, and wiring between rear HO2S terminal No. 3 and ECM connector terminal A19 for a short to ground.
  6. Turn ignition on. Connect voltmeter between breakout box pins No. 32 and 42. If voltage is about 1.2 volts, go to next step. If voltage is not about 1.2 volts, turn ignition off. Disconnect front HO2S connector. Repeat test. If voltage is now about 1.2 volts, replace front HO2S. If voltage is not about 1.2 volts, check wiring between front HO2S terminal No. 4 and ECM connector terminal A33 for a short to ground.
  7. Turn ignition off. Disconnect rear HO2S connector. Repeat test. Connect voltmeter between breakout box pins No. 34 and 42. If voltage is now about 1.2 volts, replace rear HO2S. If voltage is not about 1.2 volts, check wiring between rear HO2S terminal No. 4 and ECM connector terminal A34 for a short to ground.
  8. Turn ignition off. Wait 2 minutes. Disconnect front HO2S connector. Connect ohmmeter between HO2S connector terminals No. 3 and 4. If at least 50 k/ohms are present, check wiring between front HO2S terminal No. 4 and control module connector terminal A34 for a short circuit. If at least 50 k/ohms are not present, replace front HO2S.
  9. Turn ignition off. Wait 2 minutes. Disconnect front HO2S connector. Connect ohmmeter between HO2S connector terminal No. 4 and ground. If at least 50 k/ohms are present, go to next step. If at least 50 k/ohms are not present, check HO2S and ECM connectors for good terminal contact. Repair as necessary. Repeat test. If at least 50 k/ohms are present, system is okay, If at least 50 k/ohms are not present, check wiring between rear HO2S connector terminal No. 4 and ECM connector terminal A32 for an open circuit.
  10. Ensure ignition is off. Connect ohmmeter between front HO2S connector terminal No. 3 and ground. If ohmmeter reads about 140 ohms, go to next step. If ohmmeter does not read about 140 ohms, check HO2S and ECM connectors for good terminal contact. Repair as necessary. Repeat test. If ohmmeter reads about 140 ohms, system is okay, If ohmmeter does not read about 140 ohms, check wiring between rear HO2S connector terminal No. 3 and ECM connector terminal A33 for an open circuit.
  11. Start and idle engine. Using scan tool, go into scrolling values list. If rear HO2S signal rises above its middle value of .47 volt then maintains between .1-.9 volt within about 10 minutes, DTC was caused by poor terminal contact. If rear HO2S signal is not to specification, replace rear HO2S.
  12. Check wiring between front HO2S connector terminal No. 4 and ECM connector terminal A32 for an intermittent short to ground. Check wiring between front HO2S terminal No. 3 and ECM connector terminal A33, and between rear HO2S terminal No. 3 and ECM connector terminal A19 for an intermittent short circuit. Check wiring between rear HO2S terminal No. 4 and ECM connector terminal A34 for an intermittent short to ground. Repair as necessary.
  13. Check wiring between front HO2S connector terminal No. 4 and ECM connector terminal A32 for an intermittent short to wiring harness between front HO2S terminal No. 3 and ECM connector terminal A33. Repair as necessary.
  14. Check wiring between front HO2S terminal No. 4 and ECM connector terminal A32 for an intermittent open circuit. Check wiring between front HO2S terminal No. 3 and ECM connector terminal A33 for an intermittent open circuit. Also check ECM and front HO2S connectors for loose connections.
  15. Check wiring between front HO2S connector terminal No. 4 and ECM connector terminal A32 for an intermittent short to voltage. Check wiring between front HO2S terminal No. 3 and ECM connector terminal A33, and between rear HO2S terminal No. 3 and ECM connector terminal A19 for an intermittent short circuit to voltage. Check wiring between rear HO2S terminal No. 4 and ECM connector terminal A34 for an intermittent short to voltage.
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