Code Definition

P128A — Rocker Arm Oil Pressure Sensor (B) Stuck High

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

About P128A

P128A is a manufacturer-specific powertrain diagnostic trouble code recorded for Honda vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P128A is stored, the module has detected a signal or supply voltage higher than the expected operating range; 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.

P128A 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 rocker arm oil pressure sensor (B) signal to confirm correct oil pressure feedback for the variable valve timing or cylinder deactivation system on that bank. The sensor reports whether the commanded oil pressure has actually reached the rocker arm circuit, allowing the PCM to verify that the switching oil control solenoid has engaged or released the rocker arm as commanded. DTC P128A is set when the PCM detects the sensor signal voltage remaining above a calibrated high threshold for a specified period of time, indicating the signal is stuck hi...

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