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Home >> Jeep >> 2021 >> Grand Cherokee L Laredo, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 14 (5.7L - DTCS B1F08 To P0131) >> DTC Troubleshooting >> P0129-Barometric Pressure Out Of Range Low >> Theory Of Operation

Theory Of Operation

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The Powertrain Control Module (PCM) runs a diagnostic to check the Manifold Absolute Pressure Sensor (MAP) calibration and 5-Volt Supply circuit. It does this by reading the Barometric Pressure (BARO) when the engine is not running. The BARO reading with the engine off should fall within a predictable threshold. If the reading is below this threshold when the monitoring conditions are met, it is determined that the 5-Volt Supply was lost or the MAP Sensor is out of range.

NOTE:

Do not use shop air to clean out the MAP Sensor when diagnosing a MAP Sensor related fault as this will cause internal damage to the sensor.