P2228

P2228 sets when the BARO sensor signal voltage falls below the expected lower threshold — typically below 0.5V on a 5V reference scaled at 60-105 kPa, which would represent a barometric pressure lower than any real-world elevation (Mt. Everest sits around 33 kPa, and the OBD-II calibration won't extend that low). Low input is almost always wiring or sensor failure rather than actual ambient conditions — a short to ground on the signal wire, a failed 5V reference at the sensor, or a sensor whose internal output transistor has failed shorted. Cheapest-first: DMM the signal wire at the sensor connector with key-on engine-off — should read 4.0-4.5V at sea level (atmospheric pressure pushes the diaphragm against ambient). If the signal is at 0V with the sensor unplugged at the ECU, the harness is shorted to ground between the ECU and connector. If signal goes to 4.5V with the sensor unplugged but drops back to 0V when reconnected, the sensor itself is internally shorted. Check the 5V reference at the connector — if reference is missing, look for a shorted sensor elsewhere on the same 5V bus (TPS, MAP, accelerator pedal) that's pulling the reference down. Inspect any external MAP/BARO sensor for oil contamination from the PCV path coating the silicon element. On integrated-PCM BARO, P2228 frequently points at an internal PCM fault.

Vehicle-specific patterns: 2007-2014 Ford F-150 / Edge / Explorer 3.5L EcoBoost throws P2228 with internal-PCM BARO — when wiring is verified clean, the PCM is the failure point ($700-$1,200 with programming). 2006-2012 GM 5.3L/6.0L Vortec trucks throw P2228 from a contaminated combination MAP/BARO sensor on the intake — oil intrusion through the PCV path shorts the silicon diaphragm circuit ($65-$140 sensor + 0.5 hr labor). 2008-2014 Chrysler/Dodge 5.7L Hemi throws P2228 paired with multiple 5V-bus codes when a single sensor on the bus (often the MAP itself) fails shorted and drags the reference down — isolating one sensor at a time is the diagnostic. 2010-2015 Toyota Tundra / Sequoia 5.7L 3UR-FE throws P2228 from a chafed harness where the MAP/BARO routes past the EGR pipe. Estimated repair: $65 to $1,200.