ION, L-Series, S-Series 1999-2005

Barometric Pressure Sensor



The Barometric Pressure (BARO) sensor measures the pressure of the atmosphere. This pressure is affected by altitude and weather conditions. A diaphragm within the BARO sensor is displaced by the pressure changes that occur from varying altitudes and weather conditions. The sensor translates this diaphragm action into the voltage signal input that is used by the powertrain control module (PCM) for diagnostics and emissions control.

Removal & Installation

  1. Disconnect the Barometric Pressure (BARO) sensor harness connector.
  3. Remove the BARO sensor bracket and bolt.
  5. Remove the BARO sensor.

To install:

  1. Installation is the reverse of removal.


  1. Check the condition of the connector. Make sure the connector is firmly attached. Check for broken or bent connector pins. Repair any connector damage before continuing with troubleshooting the issue.
  3. Check the condition of the wiring to the connector. If the wiring is damaged, repair the wiring before continuing with any further tests.
  5. Connect a jumper wire between the 5-volt reference circuit of the BARO sensor and the signal circuit of the BARO sensor at the harness connector. The reading should be approximately 4.8 volts.
  7. Turn OFF the ignition for 90 seconds to allow the control modules to power down.
  9. Measure the resistance from the low reference circuit of the BARO sensor at the harness connector to a good ground with a multimeter. If the resistance is not 5 ohms, replace the sensor.

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    Fig. Barometric Pressure (BARO) sensor terminals; (A) Low reference, (C) 5 volt reference