OBD II P0109
Fault Code Definition
The Manifold Absolute Pressure Sensor/Barometric Pressure Sensor measures the rise and fall of the air pressure inside the Intake Manifold. This provides critical data needed for the Power Train Control Module (PCM) to control the Air Fuel Ratio, the Ignition Spark Timing, and many components of the Emissions Control Systems. The Manifold Absolute Pressure/Barometric Pressure Sensor converts the Intake Manifold air pressure into a voltage that is high when the Intake Manifold air pressure is high and low when the Intake Manifold air pressure drops to a vacuum. The P0109 code indicates an intermittent or erratic voltage signal from the MAP to the PCM.
Symptoms
* Check Engine Light will illuminate
* In many cases, no abnormal symptoms may be noticed
* In some cases, the engine may be hard starting and/or get poor fuel economy
* In some cases, noticeably poor engine performance may occur
Common Problems That Trigger the P0109 Code
* Manifold Absolute Pressure Sensor/Barometric Pressure Sensor is defective
* Intake Manifold vacuum leaks
* Faulty or corroded Manifold Absolute Pressure Sensor/Barometric Pressure wiring or connections
Common Misdiagnoses
* Manifold Absolute Pressure Sensor/Barometric Pressure Sensor is replaced when the real cause is a vacuum leak
* MAP Sensor is replaced when the real issue is a problematic EGR Valve
* Manifold Absolute Pressure Sensor/Barometric Pressure Sensor is replaced when the real problem is a defective Idle Air Control Motor, which causes a very low engine idle
OBD II Code P0171 and P0174
Fuel System Too Lean (Bank 1 or 2)
Our emissions expert has put together the following information about the P0171 and P0174 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.
OBD II Fault Code
* OBD II P0171
* OBD II P0174
Fault Code Definition
* OBD II P0171 Fuel System Too Lean (Bank 1)
* OBD II P0174 Fuel System Too Lean (Bank 2)
Symptoms
* Check Engine Light will illuminate
* In some cases, no adverse conditions may be noticed by the driver
* In other cases, there may be performance problems, such as a lack of power on acceleration and some "coughing" or misfiring
* The vehicle may have trouble idling, especially when warm or when sitting at a stoplight
Common Problems That Trigger the P0171 and P0174 Code
* PCM software needs to be updated
* Vacuum leaks (Intake Manifold Gaskets, vacuum hoses, PCV hoses, etc.)
* Mass Airflow Sensor (MAF)
* Plugged Fuel Filter or weak Fuel Pump
* Plugged or dirty Fuel Injectors
Common Misdiagnosis
* Oxygen Sensors