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DTC P0134: O2 Sensor 1/1 Stays At Center

NOTE: For connector terminal ID, see CONNECTOR IDENTIFICATION . For wiring diagram, see WIRING DIAGRAMS article.
NOTE: The O2 sensor 1/1 is referred to as upstream oxygen sensor in this test. Upstream oxygen sensor operation is monitored when engine is running for more than 2 minutes and engine coolant temperature is greater than 170°F (76.7°C). DTC may be stored in Powertrain Control Module (PCM) if upstream oxygen sensor signal voltage is .35-.55 volt for one minute. Possible causes are: defective upstream oxygen sensor, defective PCM, or defective connectors or wiring .
  1. Turn ignition on with engine off. Using scan tool, read Diagnostic Trouble Codes (DTCs). If global good trip counter is displayed and equal to zero, go to next step. If global good trip counter is not displayed or displayed with a value, go to step  5.
  2. Ensure ignition is off. Disconnect upstream oxygen sensor connector. Upstream oxygen sensor is located on the exhaust manifold. Turn ignition on with engine off. Using scan tool, monitor upstream oxygen sensor voltage. Upstream oxygen sensor voltage may also be referred to as 1/1 O2 sensor voltage. While monitoring upstream oxygen sensor voltage, connect jumper wire between upstream oxygen sensor connector (harness side) terminals No. 4 (Black/Dark Green wire) and No. 3 (Black/Orange wire). If upstream oxygen sensor voltage changes from 5 volts to less than one volt, go to next step. If upstream oxygen sensor voltage does not change as specified, replace upstream oxygen sensor.
  3. Using ohmmeter, check resistance between engine ground and upstream oxygen sensor connector terminal No. 3 (Black/Orange wire). If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit on Black/Orange wire between upstream oxygen sensor and PCM. PCM is located in engine compartment, between air cleaner and radiator. Perform TEST VER-5A .
  4. Disconnect jumper wire. Disconnect PCM connectors. PCM is located in engine compartment, between air cleaner and radiator. Check resistance of Black/Dark Green wire between upstream oxygen sensor connector terminal No. 4 and PCM connector terminal No. 30. If resistance is less than 5 ohms, replace PCM. Perform TEST VER-5A . If resistance is 5 ohms or more, repair open Black/Dark Green wire. Perform TEST VER-5A .
  5. Inspect wiring and connectors between upstream oxygen sensor and PCM. Inspect related wiring harnesses and connectors. Refer to Technical Service Bulletins (TSBs) for related problems. If no problems exist, test is complete. If any problems exist, repair wiring or connectors as necessary. Perform TEST VER-5A .
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