DTC Code P1109 – What does this code mean?

<ul> <li><b>Engine Light ON (or Service Engine Soon Warning Light)</b>: The illumination of the engine light indicates that the vehicle's onboard diagnostics system has detected an issue with the BARO sensor circuit being out of range high. This is a direct symptom of DTC Code P1109.</li> <li><b>Engine rough idle</b>: A rough idle can occur when the BARO sensor provides incorrect data to the engine control unit (ECU), leading to improper air-fuel mixture adjustments. This symptom is linked to the BARO sensor circuit being out of range high.</li> <li><b>Engine hesitation</b>: Engine hesitation during acceleration can be caused by the ECU receiving incorrect atmospheric pressure readings from the BARO sensor, affecting the engine's performance. This is another symptom of the BARO sensor circuit being out of range high.</li> </ul>

<ul><li>The Engine Control Module (ECM) may have outdated or incorrect software, leading to improper sensor readings.</li><li>A faulty Engine Control Module (ECM) can cause the BARO sensor circuit to register out-of-range high values.</li></ul>

<ul> <li><b>Initial Scan</b>: Use an OBD-II scanner to confirm the presence of DTC P1109 and check for any additional codes that may be related.</li> <li><b>Visual Inspection</b>: Inspect the BARO sensor and its wiring for any visible damage, corrosion, or loose connections.</li> <li><b>Check Sensor Voltage</b>: Using a multimeter, measure the voltage at the BARO sensor connector. Compare the readings to the manufacturer's specifications.</li> <li><b>Test Sensor Ground</b>: Ensure the BARO sensor has a proper ground connection by checking the ground wire for continuity.</li> <li><b>Inspect Power Supply</b>: Verify that the BARO sensor is receiving the correct power supply voltage as specified by the manufacturer.</li> <li><b>Sensor Replacement</b>: If the sensor voltage and ground are within specifications but the code persists, replace the BARO sensor.</li> <li><b>ECU Check</b>: If replacing the sensor does not resolve the issue, inspect the Engine Control Unit (ECU) for faults or consider reprogramming it.</li> <li><b>Clear Codes and Test Drive</b>: Clear the DTC codes using the OBD-II scanner and perform a test drive to ensure the issue is resolved.</li></ul>

<p>The DTC code P1109 indicates that the BARO (Barometric Pressure) Sensor Circuit is out of range high. This is a critical issue as it can affect the engine's air-fuel mixture, leading to poor performance and potential engine damage.</p><ul><li><b>Immediate Actions:</b> Inspect and possibly replace the BARO sensor.</li><li>Check the wiring and connections for any signs of damage or corrosion.</li><li>Verify the sensor's voltage and compare it to the manufacturer's specifications.</li></ul><p>Delaying repair can result in severe engine performance issues and increased emissions.</p>