Code Definition

P1133 — A/C Pressure Sensor High Voltage, or O2 Sensor Bank 1 Sensor 1 Sluggish (Slow Cross-counts)

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: GM

About P1133

P1133 is a manufacturer-specific powertrain diagnostic trouble code recorded for GM vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1133 is stored, the module has detected a signal or supply voltage lower than the expected operating range; a signal or supply voltage higher than the expected operating range; a bank-specific fault, meaning it applies only to one cylinder bank of a multi-bank engine; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1133 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

This General Motors specific code has two published meanings depending on the platform, an A/C refrigerant pressure sensor reading high voltage, or more commonly the upstream oxygen sensor on Bank 1 Sensor 1 switching too slowly. On most applications P1133 reports that the Heated Oxygen Sensor (HO2S) is sluggish, meaning its rich to lean cross counts and switching rate fall below the threshold the PCM expects during closed loop operation. A healthy upstream sensor switches rapidly between roughly 100mV and 900mV many times per second, so a lazy sensor that crosses slowly indicates contaminatio...

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