Error Code P0109: What It Means & What To Do?

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A sudden increase in the fuel consumption and the engine performance along with occasional engine stalling and not starting with improper throttle response may be an indication of problem with the MAP/BPS sensor circuit, hampering the engine’s performance, thus indicating OBD Code P0109.

OBD-II Code P0109 is defined as a Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent

Most manufacturers use a MAP sensor and a separate barometric pressure sensor. In such a case, the MAP sensor is mounted away from the engine and has a vacuum hose connected to it. The degree of engine intake vacuum is gathered by the sensor and input is given to the PCM, where it is compared with the input signal from the barometric pressure sensor, intake air temperature, and other factors to determine actual altitude (elevation above sea level). If the MAP sensor and BPS input signals vary by more than the specified degree, a P0109 will be stored and a MIL illuminated.

What causes the problem of Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent?

• Faulty or damaged MAF (Mass Air Flow) sensor
• Leakage in the Air Intake System
• Faulty BPS (Barometric Pressure Sensor)
• Open, shorted, frayed, or poor connection of the electrical wirings to the sensor and circuit.
• PCM being faulty and taking wrong readings
• Clogged/broken intake/inlet pipe

1. Mass Air Flow Sensor - A faulty mass airflow sensor will cause problems similar to low compression or low vacuum, and will also show symptoms similar to when your vehicle has low fuel pressure from a faulty fuel pump. Thus, replace damaged/faulty MAF sensor today!
2. EGR Valve & Parts - Check for bad EGR system and parts that hamper the engine performance and can cause engine stalling and not starting along with rough engine idles. Replace faulty components now!
3. Throttle Body - Throttle body is a really important component that helps the air intake system and controls the airflow in the engine. Check for faulty parts and replace them now!
4. Manifold Absolute Pressure Sensor - Faulty MAP sensor affects the fuel efficiency and the engine performance and the intake systems as well. Replace faulty MAP sensor now!
5. Barometric Pressure Sensor - Damaged/faulty BPS will transmit wrong information to the PCM or nothing at all, affecting the air intake and the fuel delivery system and thus the engine performance. Replace faulty BPS now!
6. Throttle Position Sensor - If the TPS is damaged or faulty, it may cause loss of engine power and acceleration along with reduced fuel economy. Replace faulty sensor now!
7. Diagnostic Tool - Choose from our wide variety of diagnostic tools to detect and correct the OBD code error.

Symptoms of OBD code P0109 are as follows:

Common Symptoms

• Malfunction indicator lamp (MIL)/Check Engine Light illumination
• Rough running engine
• Black smoke dispersing from tailpipe
• Hard start or stalling of engine
• Poor throttle response and acceleration
• Decreased fuel economy

The main components to look for error and correct the OBD error are following;

• Damaged Intake Manifold Gasket
• Faulty Mass Airflow Sensor
• Faulty MAP sensor
• Damaged Barometric Pressure Sensor
• Damaged EGR system
• Dirty Air Filter

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The first step for the P0109 diagnostic code is to check for Technical Service Bulletins (TSBs) that apply to your year/make/model/engine, and then visually inspect the wiring and system components.

• Do a visual inspection of all MAF sensor wiring and connectors to make sure they are intact, not frayed, broken, routed too close to ignition wires/coils, relays, motors, etc.
• Check for any obvious air leaks in the air intake system.
• Inspect the MAF sensor wires or film for any contamination such as dirt, dust, oil, etc.
• Clean the MAF and the air intake system mesh.
• Check for vacuum leaks to the MAP sensor, as it can also trigger this DTC.
• Use a scan tool to monitor real-time sensor values from the MAF sensor, O2 sensors, etc.
• The barometric pressure (BARO) that is used in order to calculate the predicted MAF value is initially based on the MAP sensor at key ON.
• Do an exhaust back pressure test to determine if the catalytic converter is clogged or not.
• Repair faulty PCM sensor that may require reprogramming.
• Replace Leaky and damaged intake/inlet pipe immediately.
• Faulty MAF (Mass Airflow Sensor) needs replacement as it directly hampers the engine performance.

Common mistakes when diagnosing the P0109 code

By far, the most common cause of a P0109 being stored is a disconnected MAF sensor. When the air filter is checked or replaced, the MAF sensor is often left disconnected. If your vehicle has recently been service, and a code P0109 is suddenly stored, suspect that the MAF sensor has simply been left unplugged.

Some of the common mistakes done while changing diagnosing the OBD code P0109 are:

• Intake manifold leak
• Mass Air Flow (MAF) sensor failure
• Powertrain Control Module (PCM) failure
• Wiring issue