P0235

P0235 indicates a circuit fault in the turbocharger boost sensor A signal, meaning the ECM cannot validate the sensor's output, often because the signal is missing entirely or stuck at an out-of-range value. Cheapest first: scan live data and verify the boost or manifold absolute pressure sensor is reading roughly 14.5 to 14.7 psi (atmospheric) at key-on-engine-off at sea level, dropping to 4 to 8 psi at idle vacuum, and rising to 20 to 35 psi under boost. A reading frozen at 0 psi or pinned at maximum indicates a circuit problem rather than a calibration drift. Disconnect the sensor and verify 5.0 volts on the reference pin, ground under 0.1 volts, and that the signal wire shows expected voltage when the sensor is unplugged (usually pulled high to 4.9 volts by the ECM). Inspect the sensor port on the intake manifold or charge pipe for oil contamination, which is common on turbo engines with PCV blow-by and which fouls the sensor diaphragm. Caveat: many platforms share the 5-volt reference between MAP, boost, and other sensors; a single shorted sensor can take down the whole reference bus and set P0235 plus several others.

Vehicle-specific patterns: Ford 6.0L and 6.4L Power Stroke (2003-2010) commonly sets P0235 from oil-fouled MAP/boost sensors, requiring sensor cleaning or replacement every 50,000 miles in heavy-duty use. Cummins ISB 5.9L and 6.7L (2003-2018 Ram HD) sees P0235 from boost sensor connector corrosion and wiring chafe at the turbo. VW/Audi 2.0T TSI (2008-2017) sets P0235 from a failed manifold pressure sensor, a $50 part. Chevy Cruze 1.4T LUV (2011-2019) sees P0235 from intake manifold boost sensor failure as a known weak point. Estimated repair: $40 to $400.