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DTC P0134/16518 - Ho2S Circuit No Activity (Bank 1 Sensor 1)

NOTE: DTC is set when Engine Control Module (ECM) does not recognize pre-catalyst Heated Oxygen Sensor (HO2S) signal.
  1. Inspect pre-catalyst HO2S connector for looseness and/or corrosion. Repair sensor connector as necessary. Erase DTC memory and test drive vehicle. See CLEARING DTCS  in this article. Recheck DTC memory and verify DTC does not reset. If DTC resets, go to next step. If sensor connector is okay, go to next step.
  2. Turn ignition off. Disconnect pre-catalyst HO2S connector. Using a DVOM, check continuity between pre-catalyst HO2S connector terminals No. 3 and 4 with engine idling at normal operating temperature. Voltage should be .2-.8 volt. Go to next step.
  3. Increase engine speed several times. Voltage should change from .2 volt (lean mixture) to .9 volt (rich mixture). If voltage is as specified, go to next step. If voltage is not as specified, replace HO2S. Erase DTC memory and test drive vehicle. See CLEARING DTCS in this article. Recheck DTC memory and verify DTC does not reset. If DTC resets, go to next step.
  4. Turn ignition off. Disconnect ECM connector. Connect Test Box (VAG 1598/18) to ECM wiring harness. Terminal assignments of test box are identical to ECM connector's.
  5. Using DVOM, check resistance between pre-catalyst HO2S connector terminal No. 3 and test box socket No. 42, and pre-catalyst HO2S connector terminal No. 4 and test box socket No. 20. Resistance should be less than 1.5 ohms. If resistance is as specified, go to next step. If resistance is not as specified, locate and repair open circuit between HO2S and ECM. Erase DTC memory and test drive vehicle. See CLEARING DTCS in this article. Recheck DTC memory and verify DTC does not reset. If DTC resets, go to next step.
  6. Check resistance between pre-catalyst HO2S connector terminal No. 3 and test box socket No. 56, and pre-catalyst HO2S connector terminal No. 4 and test box socket No. 56. Resistance should be infinite (no continuity). If resistance is as specified, go to next step. If resistance is not as specified, locate and repair short circuit between HO2S and ECM. Erase DTC memory and test drive vehicle. See CLEARING DTCS  in this article. Recheck DTC memory and verify DTC does not reset. If DTC resets, go to next step.
  7. Replace HO2S. Erase DTC memory and test drive vehicle. See CLEARING DTCS in this article. Recheck DTC memory and verify DTC does not reset. If DTC resets, go to next step.
  8. Replace faulty ECM. Test drive vehicle. Recheck DTC memory and verify DTC does not reset. If DTC resets, repeat testing procedure.
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