P0112

P0112 means IAT signal voltage is below the floor — under roughly 0.2V on a standard NTC thermistor, which translates to a reported intake air temperature above 250F. The ECM treats this as a short to ground or a failed sensor. Cheapest-first ladder: unplug the IAT connector (or MAF connector if IAT is integrated) and check whether the scan tool reading swings to -40F (which means the ECM is seeing open-circuit, confirming the sensor was shorting low internally and replacement fixes it); if the scan tool still reads 250F+ with the connector unplugged, the signal wire is shorted to ground in the harness — inspect chafe points at the valve cover, intake manifold ribs, and where the harness crosses any sharp metal; verify the 5V reference at the connector is 4.9-5.1V key-on (IAT typically uses the same 5V bus as TPS and MAP on most platforms); on integrated MAF/IAT sensors a P0112 paired with any P010x MAF code usually means the entire MAF unit needs replacement since the IAT element is part of the same circuit board; expected voltage at 70F ambient is 2.5-3.0V, at 200F hot-soak is 0.5-1.0V, and shorted-to-ground is essentially 0V. Do not replace an integrated MAF for P0112 alone before checking the harness for a chafe — a $5 wire repair is faster than a $300 MAF.

Vehicle-specific patterns: 2004-2010 Ford F-150 5.4L 3V sees P0112 from the same MAF harness chafe at the valve cover that causes P0100/P0104, since IAT is integrated; 2007-2014 GM 5.3L Silverado sees P0112 from the separate IAT sensor in the intake tube failing internally with the element shorting to housing ground; 2005-2010 Subaru EJ25 sees P0112 from corroded MAF/IAT connector pins where moisture intrusion shorts the IAT signal to a 12V or ground pin; 2003-2008 Honda J35 sees P0112 from internal MAF/IAT circuit board failure where the IAT thermistor shorts and the entire MAF must be replaced. Estimated repair: $15 to $350.