Code Definition

P1154 — H02S Transition Time Ratio Bank 2 Sensor 1

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

About P1154

P1154 is a manufacturer-specific powertrain diagnostic trouble code recorded for Isuzu vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1154 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.

P1154 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 upstream heated oxygen sensor (H02S) on Bank 2 Sensor 1 must transition cleanly between its lean and rich output as the mixture crosses stoichiometric on the cylinder bank that does not contain cylinder one. DTC P1154 sets when the ECM measures the ratio between the lean to rich and rich to lean transition times on this sensor and finds it outside the acceptable window, indicating an asymmetric or slow response. The transition time ratio is a sensitive early indicator of sensor aging on Bank 2. Contamination, a Bank 2 exhaust leak, a weak heater, or wiring resistance can all skew the trans...

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