P0776

P0776 is the performance code for Pressure Control Solenoid B, meaning the electrical circuit tests fine but the commanded pressure does not produce the expected hydraulic response: line pressure too high, too low, or unresponsive to PWM duty-cycle changes. Cheapest-first: install a transmission line-pressure gauge at the test port and compare actual pressure against spec across the duty-cycle range. On a healthy unit, EPC duty changes should produce smooth proportional pressure changes (for example, 4L80E should sweep roughly 60 to 250 psi as EPC current sweeps from 1 A to 0 A). If pressure is stuck high regardless of command, the solenoid is stuck closed or the valve bore is sticking; stuck low points to a stuck-open solenoid, worn pump, or internal leak. Bench-resistance the solenoid against spec (3 to 7 ohms typical for GM force motors, 4 to 6 ohms for most Toyota/Chrysler PC solenoids). Inspect the EPC screen/filter for debris and check the boost valve and pressure regulator valve bores for wear, since these are extremely common P0776 root causes on high-mileage units. Caveat: a worn pump or excessive internal leakage will mimic a failed PC solenoid by dropping line pressure below command; always confirm with a pressure gauge before condemning the solenoid.

Vehicle-specific patterns: 2002 to 2008 Chevrolet Trailblazer with 4L60E sets P0776 from boost valve and pressure regulator bore wear in the pump, repaired with Sonnax oversized boost valve kit rather than pump replacement. 2004 to 2010 Ford Expedition/F-150 with 4R75W/4R70W trips P0776 from a worn pressure regulator valve bore, with Ford TSB 09-2-7 documenting harsh shifts and code. 2005 to 2009 Subaru Outback/Legacy 5EAT sets the equivalent code from duty solenoid C wear, a known issue covered by Subaru TSB 16-78-08. 2003 to 2010 Toyota Tundra with A750F trips P0776 from internal SLT solenoid contamination and valve body sleeve scoring. Estimated repair: $300 to $1,600.