P0236

P0236 means the boost pressure sensor reading is out of range or does not correlate with other inputs, typically detected when the ECM compares boost pressure against throttle position, MAF airflow, and commanded boost and finds an implausible relationship. Cheapest first: at key-on-engine-off, verify the boost sensor reads atmospheric pressure (roughly 14.5 to 14.7 psi at sea level, lower at altitude); a reading more than 1 psi off atmospheric indicates the sensor is drifting. Compare boost sensor reading at idle to the MAP sensor reading (if equipped separately); they should agree within 0.5 psi at idle vacuum. Look for vacuum or pressure leaks in the line that supplies the sensor: a cracked silicone line or loose hose clamp on the charge pipe will give a low reading under boost and set P0236. Smoke-test the intake tract from the turbo outlet to the throttle body; even a 1/8 inch crack in an intercooler hose or boot will be visible and will trigger this code under load. Caveat: a slipped or partially clogged DPF on diesel applications can cause boost reading anomalies that mimic sensor performance faults.

Vehicle-specific patterns: Ford 6.0L Power Stroke (2003-2007) sees P0236 from carbon-fouled MAP sensors and cracked intercooler hoses. GM Duramax LML 6.6L (2011-2016) sets P0236 from boost sensor fouling caused by EGR soot, addressed in GM Bulletin 13-06-04-007. Subaru WRX and STI EJ255/EJ257 (2008-2021) sees P0236 from cracked intercooler Y-pipes and silicone couplers, a common modding-induced fault. Volvo T5 and T6 (2003-2016 S60, XC90) sets P0236 from PCV system failure flooding the boost sensor with oil. Estimated repair: $40 to $600.