DTC P0133: Ho2S1 Circuit - Slow Response: Description

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The Heated Oxygen Sensor 1 (HO2S1) is an electrical source that responds to oxygen content in exhaust manifold. When sensor reaches approximately 600°F (316°C), it produces a voltage based on the difference in oxygen between atmosphere and exhaust gas. ECM sends a bias voltage (399-499 millivolts) on signal line, which is pulled up through high resistance. When HO2S1 is cold, it produces no voltage and has extremely high internal resistance. Internal resistance of sensor is much more than the resistance of the bias pull-up resistor. However, when sensor heats up, it produces voltage that overrides bias voltage. This voltage is read by ECM to determine a rich/lean HO2S1 signal used to adjust injector pulse width. Under normal conditions, low sensor voltage means high oxygen content/lean air/fuel mixture and vice versa. Normal sensor readings will fluctuate 10-1065 millivolts. DTC sets when HO2S1 signal rich to lean or lean to rich average response time is too slow.