DTC P1133: Powertrain Control Module (PCM) CIRCUIT - INSUFFICIENT SWITCHING - SENSOR 1: Description

WARNING: This page is about a different car, the 2002 Pontiac Aztek and 2002 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started, the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates above and below bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and provide an accurate voltage signal. This DTC will set if the HO2S 1 voltage did not switch enough times during a calibrated time period. Each HO2S 1 has the following circuits:

HO2S 1 high signal.
HO2S 1 low reference.
HO2S 1 heater ignition voltage.
HO2S 1 heater low control Low reference loop.