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DTC P0133: 1/1 O2 Sensor Slow Response: Testing

NOTE: 1/1 HO2S may also be referred to as an upstream oxygen sensor. On models with Federal emissions, 1/1 HO2S is located in exhaust downpipe in front of catalytic converter. On models with Calif. emissions, 1/1 HO2S is located in front exhaust manifold.
  1. Using scan tool, read DTCs. If GOOD TRIP counter is displayed for DTC P0133 and displayed count is "0", go to next step. If GOOD TRIP counter is not displayed for DTC P0133 or displayed count is not "0", go to step  6 .
  2. Start engine and allow it to idle. Check exhaust system for leaks between engine and 1/1 HO2S. Repair exhaust system leaks as necessary. If exhaust system is okay, go to next step.
  3. Using voltmeter, backprobe Black/Dark Green wire between 1/1 HO2S harness connector and terminal No. 24 at PCM C1 harness connector. See Figure . If voltage is less than 0.1 volt, go to next step. If voltage is 0.1 volt or more, repair poor connection causing high resistance on 1/1 HO2S signal circuit (Black/Dark Green wire) between 1/1 HO2S and PCM.
  4. Using voltmeter, backprobe Brown/Yellow wire between 1/1 HO2S harness connector and terminal No. 4 at PCM C1 harness connector. See Figure . If voltage is less than 0.1 volt, go to next step. If voltage is 0.1 volt or more, repair poor connection causing high resistance on 1/1 HO2S ground circuit (Brown/Yellow wire) between 1/1 HO2S and PCM.
  5. At this time, 1/1 HO2S is assumed to be defective. Replace 1/1 HO2S.
  6. At this time, conditions for DTC to set do not exist or fault is an intermittent problem. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Using scan tool, monitor 1/1 HO2S voltage while wiggling connectors and wiring harness from 1/1 HO2S to Powertrain Control Module (PCM). PCM is located in engine compartment on left front fender, near radiator support. If voltage changes while wiggling connectors and wiring harness, repair connectors and wiring harness where wiggling caused voltage to change. If voltage does not change, review FREEZE FRAME data using scan tool. Attempt to duplicate condition that caused DTC to set by paying special attention to the conditions during which 1/1 HO2S is monitored. Check for any related technical service bulletins that may apply. Visually inspect related connectors and wiring harness. Repair connectors and wiring harness as necessary. See WIRING DIAGRAMS article. If no problems are indicated, test is complete.
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