Atmospheric Pressure Sensor (Pa Sensor)
- Unplug control unit wiring harness connector and install system checker harness. Turn ignition on. On all models except Prelude, connect digital voltmeter positive probe to C9 terminal of system checker harness. Connect negative probe to C12 terminal. Voltmeter should indicate 2.76-2.96 volts. See Fig 1 .
- If voltages are not within specifications, check for open or short circuit between ECU and atmospheric pressure sensor. Replace sensor if necessary.
- On Prelude, connect positive lead of digital voltmeter to C13 terminal and negative lead to C12 terminal. If voltage is not 4.75-5.25 volts, substitute with known-good ECU. If voltage is still not as specified, replace ECU. If voltage is as specified, connect positive lead to C9 terminal and negative lead to C12 terminal.
- If voltage is 2.76-2.96 volts, replace ECU. If voltage is not as specified, repair wiring between PA sensor and ECU. If wiring is okay, replace PA sensor.