P0105

P0105 is the general MAP/BARO circuit fault — the ECM cannot read a coherent pressure signal, distinct from the range/performance P0106 and the high/low input P0107/P0108. On speed-density engines (Chrysler Hemi, GM LS without MAF, most diesels) a P0105 will put the engine in severe limp mode because the ECM has no way to calculate load. Cheapest-first ladder: locate the MAP sensor (intake manifold top on most gas engines, intake elbow on Cummins/Duramax/Powerstroke), unplug the connector, and inspect for oil contamination in the connector body (a soaked connector means the MAP vacuum port is pulling oil mist past a failed PCV system and the sensor is likely also internally fouled); verify the 5V reference with key-on engine-off, should be 4.9-5.1V; verify ground integrity under 0.1V drop; with engine at warm idle, MAP voltage on most GM 3-bar sensors reads 1.0-1.5V at idle (roughly 30-40 kPa) and 4.0-4.7V at WOT (95-105 kPa absolute), 1-bar sensors on most imports read 1.0-1.5V at idle and 4.5-4.8V at WOT/key-on-engine-off (since atmospheric is roughly 100 kPa). A MAP reading 4.5V at idle on a gas engine is signaling atmospheric pressure inside the manifold, which means either a disconnected vacuum line to the sensor, a clogged vacuum port, or a stuck-open throttle plate — do not replace the sensor before tracing the vacuum reference.

Vehicle-specific patterns: 2005-2010 Chrysler/Dodge 5.7L Hemi sets P0105 frequently from oil saturation of the MAP sensor through a failing PCV — the sensor sits on top of the intake and the port wicks oil mist directly into the silicon element; 2007-2014 GM 5.3L Silverado/Tahoe places the MAP under the intake manifold valley cover and a P0105 here almost always means the intake gasket is leaking coolant onto the sensor or its connector; 2007-2018 Cummins 5.9L/6.7L Ram trucks see P0105 from soot caking the MAP sensor port in the intake horn, requiring a clean rather than replacement on the first occurrence; 2008-2014 VW/Audi 2.0T TSI sees P0105 from the integrated MAP/IAT sensor in the intake manifold failing internally around 80-120k miles. Estimated repair: $40 to $350.