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Home >> Volvo >> 1995 >> 850 Base, 4D Sedan, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - Turbo >> Diagnostic Trouble Code Testing >> MOTRONIC 4.3 Control System >> Code 1-5-3: Rear HO2S Signal

Code 1-5-3: Rear HO2S Signal

  1. If Codes 5-2-2 or 2-1-2 are stored, perform diagnosis for these codes first. If fault is permanent or intermittent and signal is too high, perform diagnosis as per Code2-1-2. If fault is permanent and signal is too low, go to next step. If fault is permanent and signal is faulty, go to step 8). If fault is intermittent and signal is too low, go to step 9). If fault is intermittent and signal is faulty, go to step 10).
  2. Turn ignition off. Wait 2 minutes. Disconnect rear HO2S Gray connector. Connect an ohmmeter between HO2S connector terminal No. 4 and ground. If ohmmeter shows about 100 k/ohms, go to step 4). If ohmmeter shows infinite resistance, go to next step. If ohmmeter shows about zero ohms, check wiring between rear HO2S connector terminal No. 4 and ECM terminal A34 for a short circuit to ground.
  3. Turn ignition off. Disconnect HO2S connector. Ensure ECM connector terminal contacts are clean and tight. Reconnect ECM. Connect an ohmmeter between HO2S connector terminal No. 4 and ground. If ohmmeter reads about 100 k/ohms, source of code is poor contact at ECM connector. If ohmmeter does not read about 100 k/ohms, check wiring between rear HO2S connector terminal No. 4 and ECM terminal A34 for an open circuit.
  4. Turn ignition off. Disconnect rear HO2S connector. Connect an ohmmeter between HO2S connector terminal No. 3 and ground. If ohmmeter reads about 200 ohms, go to step 7). If ohmmeter shows infinite resistance, go to next step. If ohmmeter shows about zero ohms, go to step 6).
  5. Turn ignition off. Disconnect rear HO2S connector. Ensure ECM connector terminals are clean and tight. Reconnect ECM. Connect an ohmmeter between HO2S connector terminal No. 3 and ground. If ohmmeter reads about 200 ohms, source of code is poor contact in ECM connector. If ohmmeter does not read about 200 ohms, check wiring between rear HO2S connector terminal No. 3 and ECM terminal A19 for an open circuit.
  6. Turn ignition off. Disconnect rear HO2S connector. Disconnect front HO2S Black connector. Connect an ohmmeter between rear HO2S connector terminal No. 3 and ground. If ohmmeter reads about 200 ohms, test system using a new front HO2S. If ohmmeter does not read about 200 ohms, check wiring between front HO2S connector terminal No. 3 and ECM terminal A33, and wiring between rear HO2S connector terminal No. 3 and ECM terminal A19 for a short to ground.
  7. Turn ignition off. Ensure rear HO2S is connected. Start and run engine at idle. Check voltage at rear HO2S. Voltage signal should have left its bottom setting (-.165 volt) and stabilized between .1-.9 volt within about 10 minutes. If reading is okay, source of code is poor contact at rear HO2S connector. If reading is not okay, retest using new rear HO2S.
  8. If fault is permanent and signal is faulty, turn ignition off. Wait about 2 minutes. Disconnect rear HO2S Gray connector. Connect an ohmmeter between HO2S connector terminals No. 3 and 4. If ohmmeter reads infinite resistance, check wiring between rear HO2S connector terminal No. 4 and ECM connector terminal A34 for a short circuit to rear HO2S connector terminal No. 3 and ECM connector terminal A19. If ohmmeter does not read infinite resistance, test using new HO2S.
  9. If fault is intermittent and signal is too low, check wiring between rear HO2S connector terminal No. 4 and ECM terminal A34, and between rear HO2S connector terminal No. 3 and ECM terminal A19 for an open circuit. Check ECM and rear HO2S connector for loose connection. Check wiring between rear HO2S connector terminal No. 4 and ECM terminal A34 for an intermittent short circuit to ground. Also check wiring between front HO2S connector terminal No. 3 and ECM terminal A33, and wiring between rear HO2S connector terminal No. 3 and ECM terminal A19 for an intermittent short circuit to ground.
  10. If fault is intermittent and signal is faulty, check wiring between rear HO2S connector terminal No. 4 and ECM connector terminal A34 for an intermittent short circuit of wire between rear HO2S connector terminal No. 3 and ECM connector A19.
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