What does it mean?
OBD II fault code P0105 is defined as “Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction”, and is set when the Powertrain Control Module detects a signal voltage from the MAP (Manifold Absolute Pressure) sensor that is either abnormal with regard to the current engine load and/or throttle position, or a signal from the MAP sensor that does not correlate with the signal voltage from the TPS (Throttle Position Sensor).
As engine loads/speeds change, the pressure (or vacuum) in the intake manifold also changes in response to the varying demand. As a result, the MAP sensor generates signal voltages based on the pressure changes, which the PCM (Powertrain Control Module) uses to calculate appropriate fuel delivery strategies and adaptations to the ignition timing to keep the engine performing at peak efficiency.
To monitor the accuracy of MAP sensor readings the PCM uses other sensors, most notably the TPS (Throttle Position Sensor) to verify the correct operation of the MAP sensor. Thus, should the PCM detect a “mismatch” between the signals from the MAP and TPS sensors, the PCM will recognize a fault condition, and code P0105 will be set.
In practice though, the TPS sensor “leads” the MAP sensor, in the sense that the PCM expects to detect a change in the signal voltage from the MAP sensor immediately the throttle position changes, which change produces a signal voltage against which the subsequent correct functioning (or otherwise) of the MAP sensor can be gauged.
However, this scenario assumes that both the MAP and TPS sensors and associated circuits are functioning properly, but it is possible for a defective TPS sensor to also cause code P0105 to be set when its signal voltage does not match that of the MAP/BARO sensor. The images below show typical MAP/MAF/TPS sensors, but note that these images are for informational purposes only.
However, although the designs of these sensors differ from vehicle to vehicle, any or all three sensors shown here could be implicated in OBD II fault codes that are closely related to P0105- i.e., P0106, P0107, P0108, and P0109. Typical MAP sensor MAP sensors are always located directly on the intake manifold, where they monitor changes in manifold pressure.
Typical MAF sensor MAF sensors are always located directly in the inlet tract, although their actual position in the tract can differ from vehicle to vehicle. Note the elements that generate a signal voltage when inlet air passes over them. Other applications could have more, or fewer elements. Typical TPS (Throttle Position) sensor Throttle position sensors are located on the throttle body, which should not be confused with the MAF sensor that is located elsewhere in the inlet tract.
In this application, the actual TPS is the black plastic unit secured to the aluminum throttle body with two screws. Note the connector with three wires leading out of it. Note: “Circuit Malfunction” indicates that there is a malfunction in the control circuit, as opposed to a fault in a sensor or other component.
With “Circuit Malfunction” codes, replacement of sensors and components in the affected circuit will almost never resolve the problem, since as the code suggests, the trouble is in the circuit . This distinction between “circuit” and “sensor/component” is a great help to anyone trying to diagnose a circuit malfunction code, since it narrows the list of possible causes down considerably.