P0845

P0845 covers transmission fluid pressure sensor B, the secondary pressure transducer used to monitor a specific circuit such as line, TCC apply, or clutch pack feed depending on the transmission family. The diagnostic ladder mirrors sensor A but with an added rationality step: most TCMs cross-check A and B against each other, so a P0845 paired with no P0840 usually means B is wrong and A is right. Cheapest first, scan-tool both sensors side by side at idle in Park, then again during a 3-2 downshift; sensor B should track within 10-15 psi of sensor A on shared-circuit designs or hold its own commanded pressure on dedicated-circuit designs. Caveat: a substantial number of P0845 codes are actually internal valve-body wear, not a sensor fault; if the sensor reads a real but out-of-spec pressure, the EPC or pressure regulator valve is the underlying cause.

Vehicle-specific patterns: 2008-2013 GM 6T70/6T75 in Acadia, Traverse, Enclave, and Malibu sees P0845 from a worn pressure regulator valve in the valve body, not a true sensor failure, and the Sonnax oversize PR valve kit is the durable repair. 2011-2017 Chrysler Town & Country and Ram with the 62TE has a known TCC apply pressure sensor B failure that sets P0845 alongside torque converter shudder. 2013-2018 BMW with ZF 8HP45 and 8HP70 throws P0845 from a mechatronic sleeve fluid leak that contaminates the sensor signal. 2015-2020 Ford with the 6F35 in Escape, Edge, and Fusion sees a true sensor-only failure inside the main control body. Estimated repair: $500 to $2400.