What does it mean?
P1109 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Barometric Pressure (BARO) Sensor Circuit Out of Range High .
Symptoms
- Check engine light on with an implausible barometric value in live data
- Over-rich mixture with black smoke and a heavy fuel smell
- Reduced power, hesitation and poor throttle response
- Rough idle that improves only slightly as the engine warms
- Noticeably higher fuel consumption
- Emissions test failure, and long-term risk of catalytic converter damage from the rich mixture
Likely causes
- Drifted sensor element that reports a pressure higher than the atmosphere can produce
- Lost or high-resistance ground raising the whole signal level
- Short between the signal wire and the reference or a battery-fed circuit
- Moisture inside the connector creating a leakage path to the reference pin
- Wrong sensor fitted with a different pressure range or calibration
- On systems where the value is learned from the manifold sensor at key-on, a leaking or blocked manifold connection distorting the learned reference
- Faulty module input as the final possibility
How to fix it
- Compare the barometric value with the known atmospheric pressure and with the MAP reading taken with the ignition on and the engine stopped
- Unplug the sensor and confirm the reference voltage and ground quality at the connector
- Voltage-drop test the ground path, since a poor ground is the most common reason for an inflated reading
- Inspect the connector and loom for moisture, corrosion and chafing against a live circuit
- Verify that the fitted sensor is the correct part for the engine, especially after previous repair work
- Check the manifold connection and hose on systems that derive the barometric value from the manifold sensor
- Replace the sensor if the value stays implausible with a good supply and ground, then confirm normal fuel trims after a drive cycle