Technical Description of OBD-II Trouble Code
Malfunction in the Manifold Absolute Pressure/Barometric Pressure Circuit
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The MAP (Manifold Absolute Pressure) sensor is a component of the fuel management system. It responds to changes in engine manifold pressure. The PCM (Powertrain Control Module) continuously monitors the MAP sensor to ensure proper engine operation. Changes in engine load require adjustments in the amount of fuel injected, ignition timing, and other factors.
An engine under load has higher manifold pressure (or less vacuum) compared to an engine that is coasting. As the load changes, the voltage signal from the MAP sensor to the PCM also changes. However, to verify the operation of the MAP sensor, the PCM relies on information from other sensors.
For instance, the PCM compares the signal from the TPS (Throttle Position Sensor) to the MAP signal to ensure that the MAP signal is not “sticking”. If the PCM does not detect an immediate change in the MAP sensor following a change in the throttle pedal sensor, it indicates a problem with the MAP sensor and sets the P0105 code. Similarly, if the TPS indicates that the engine is under load, but the MAP signal indicates that the engine is “coasting”, it indicates a problem with either the MAP sensor or the TPS and sets the P0105 code.
Symptoms
The symptoms of a P0105 check engine light code may include:
A typical MAP sensor
Causes
A P0105 DTC could be caused by:
Possible Solutions
Using a scanner or code reader, turn the ignition on and the engine off. What is the voltage reading of the MAP sensor? At sea level, it should be around 4 Volts. If you are at a higher altitude, it should decrease by about half a volt for every 1,000 ft. of altitude (this may vary depending on the model). If your vehicle has a separate MAF (Mass Air Flow) sensor, it usually includes a Barometric pressure reading. In that case, the Baro reading should match the MAP reading since both sensors measure ambient air pressure. If they are roughly equal, check if there is Freeze Frame data available for the MAP sensor.
NOTE: Freeze Frame data is recorded by the PCM when a fault occurs. It captures the readings of various PIDS (parameter identifiers) that can be used to troubleshoot the issue. It is like a recording of the problem as it occurred. At idle, a typical MAP sensor voltage reading should be around a volt, and at WOT (wide open throttle), it should reach 4.5 to 5 Volts. As for the TPS, at idle, the voltage reading is about 1 Volt or less. As the throttle is opened, the reading increases to 4.5 Volts at WOT. Do the two readings make sense? For example, if the Freeze Frame data shows a TPS reading of 2.5 Volts (indicating partial throttle), does the MAP sensor indicate a reading that is not at either extreme? By comparing the MAP reading to the TPS reading when the problem occurred, you can identify what happened.
If you do not have access to Freeze Frame data, check if the MAP sensor voltage changes when you apply vacuum to it. You can do this by using your mouth or a vacuum pump. The voltage should increase as you apply vacuum. If the reading does not change, ensure that there are no obstructions in the hose leading to the sensor. If the hose is clear, it is likely that the MAP sensor is faulty, although other factors may still be causing the problem. Is the MAP sensor voltage stuck at less than 0.5 Volts? Then:
NOTE: This code should not set if the MAP is stuck at an extremely low voltage. However, I am including it because it is not possible to know for certain which vehicles may set a P0105 due to a low voltage condition.
Is the MAP sensor voltage stuck at the full 4.5 volts? Then:
MAP sensor codes include P0106, P0107, P0108, and P0109.
