Code Definition

P1157 — O2 Sensor Rich or High Voltage (Bank 2 Sensor 2)

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

About P1157

P1157 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 P1157 is stored, the module has detected 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.

P1157 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 applies to the Bank 2 Sensor 2 oxygen sensor, the downstream sensor mounted after the catalytic converter on the second cylinder bank, and it reports the sensor reading rich or high voltage. P1157 sets when the PCM sees the Bank 2 Sensor 2 signal biased high, staying near the rich end rather than the steadier mid range voltage a healthy post catalyst sensor normally shows. A persistently high reading can indicate a contaminated sensor, a signal wire shorted to voltage, or a genuinely rich exhaust passing through the converter on that bank. Because the rear sen...

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