The atmospheric pressure sensor, commonly referred to as the Barometric Pressure or PA sensor, measures ambient air pressure. Unlike a Manifold Absolute Pressure (MAP) sensor, the PA sensor operates within a narrow range centered around standard atmospheric pressure.

Functionality#

The ECU utilizes data from the PA sensor to calculate air density. This allows the engine management system to dynamically adjust fuel trim and ignition timing to compensate for variations in altitude or significant changes in weather conditions.

Note

In most OBD-series Honda ECUs, the PA sensor is integrated directly onto the ECU mainboard.

Technical Specifications#

The sensor provides a voltage signal to the ECU that corresponds to the current barometric pressure.

• Primary Use: Altitude compensation and air density correction.
• Operating Range: Narrow-band atmospheric pressure.
• Integration: Internal to the ECU housing.

Troubleshooting#

If the ECU detects an out-of-range signal from the PA sensor, it may trigger a diagnostic trouble code (DTC) related to the barometric pressure circuit.

Common Symptoms of Failure#

• Poor fuel economy at high altitudes.
• Rough idle or hesitation during rapid changes in elevation.
• Rich or lean running conditions inconsistent with engine load.

Warning

When inspecting the internal PA sensor, ensure the ECU case is handled in an ESD-safe environment to prevent damage to sensitive surface-mount components.