Code Definition

P1173 — HO2S Bank 2 Sensor 1 Circuit Fixed (Bank 2 Sensor 1)

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

About P1173

P1173 is a manufacturer-specific powertrain diagnostic trouble code recorded for Mazda vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1173 is stored, the module has detected 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.

P1173 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

The Bank 2 Sensor 1 upstream heated oxygen sensor (HO2S) supplies the Powertrain Control Module (PCM) with a switching voltage used to trim fuel for Bank 2 in closed loop. DTC P1173 sets when the PCM finds the Bank 2 Sensor 1 circuit fixed, with the signal held at a steady value instead of switching between rich and lean. This typically results from an aged or contaminated sensor that can no longer react, a wiring fault holding the signal, or a heater fault keeping the sensor too cold. On V engines Bank 2 is the bank that does not contain cylinder number one. The driver may notice poorer econo...

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