P0111

P0111 means the Intake Air Temperature sensor signal is electrically valid but does not correlate with engine coolant temperature, time since start, and ambient conditions — for example, IAT reading 180F at cold start when ECT is 75F and the engine has been sitting overnight. This is a rationality fault, not a circuit fault. Cheapest-first ladder: with the engine cold and key-on engine-off, compare IAT, ECT, and ambient air temp on the scan tool — all three should be within 5-10F of each other on a fully cold-soaked vehicle; if IAT reads 50-100F higher than ECT at cold start, the IAT element is heat-soaked or contaminated; on Toyota/Honda where IAT is integrated into the MAF housing, clean the MAF with CRC MAF cleaner ($10) since IAT contamination usually comes from the same source as MAF contamination; on GM trucks where IAT is a separate sensor in the intake tube, pull the sensor and inspect for oil film on the element (PCV system pushing oil mist past the sensor); voltage check at idle on a typical NTC thermistor IAT — 70F ambient should read roughly 2.5-3.0V, 200F intake air during hot-soak should read 0.5-1.0V. P0111 is the code that catches sensor drift before it goes hard-fault, so cleaning is the right first move on most platforms.

Vehicle-specific patterns: 2003-2009 Toyota Camry/Tacoma/4Runner with integrated MAF/IAT sees P0111 from the same hot-wire contamination that causes P0101, and CRC MAF cleaner addresses both; 2007-2014 GM 5.3L Silverado/Sierra sees P0111 from oil mist on the separate IAT sensor in the intake tube from AFM blow-by, requiring sensor clean or replacement; 2005-2012 Honda Accord/Pilot J-series sees P0111 paired with MAF aging on the integrated MAF/IAT unit; 2008-2014 VW/Audi 2.0T TSI sees P0111 from the integrated MAP/IAT in the intake manifold drifting high before failing fully. Estimated repair: $10 to $300.