C0 Slow Left Bank Upstream HO2S During Catalyst Monitor

Slow Left Bank Upstream HO2S During Catalyst Monitor:

Trouble Code Number
- Scan tool C0 (192)
- General scan tool P0133

Fault Message
- Slow Left Bank Upstream HO2S During Catalyst Monitor

Background
- Effective control of exhaust emissions is achieved by an oxygen feedback system, of which the most important element is the left bank upstream heated oxygen sensor, which is located in the exhaust path. Once the sensor reaches its normal operating temperature of 300 - 350°C (572 - 662°F), it generates a voltage inversely proportional to the amount of oxygen in the exhaust. This voltage is used to calculate the fuel injector pulse width, which maintains the optimum 14.7 to 1 air/fuel (A/F) ratio that is required for the catalytic converter to best control exhaust emissions. Response rate is the time required for the sensor to detect changes in the exhaust gas oxygen content; it switches from lean to rich if it is exposed to a richer than optimum A/F mixture, or vice versa. The heated oxygen sensor output voltage ranges from 0 to 1 volt. A good sensor easily generates an output voltage in this range as it is exposed to different oxygen concentrations. To detect a shift in the A/F mixture (lean or rich), the output voltage has to change beyond a threshold value. A malfunctioning sensor could have difficulty changing beyond the thresholds.

Range of Check
- With the engine running, coolant greater than 76°C (170°F), open throttle, steady to slightly increasing vehicle speed 29 km/h (18 mph), with a light load on the engine, for a period no less than five minutes.

Set Condition
- The left bank upstream heated oxygen sensor signal voltage is switching from below 0.39 volt to above 0.6 volt and back fewer times than required.

Probable Cause
- Exhaust leak.
- Fuel contamination.
- Weak left bank upstream heated oxygen sensor with deteriorated catalyst.
- Dirt/moisture/grease inside connector.
- Engine mechanical.