Code Definition

P1151 — Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank 2

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

About P1151

P1151 is a manufacturer-specific powertrain diagnostic trouble code recorded for Ford vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1151 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.

P1151 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 Powertrain Control Module (PCM) monitors the upstream Heated Oxygen Sensor (HO2S) on Bank 2 to manage closed loop fuel control and to confirm the sensor switches normally between rich and lean. DTC P1151 sets when the Bank 2 upstream sensor signal stays biased toward lean and fails to switch as expected, so the PCM cannot maintain correct fuel control on that bank. Bank 2 is the cylinder bank that does not contain cylinder number 1, and the upstream sensor sits ahead of the catalytic converter where it reads exhaust oxygen content. The lean indication can come from a genuine air to fuel im...

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