P0776 (Pressure Control Solenoid B Performance or Stuck Off) and P0778 (Pressure Control Solenoid B Electrical) are two of the most common transmission codes you'll see on RE5R05A-equipped Nissan and Infiniti vehicles, and they're frequently misdiagnosed because the relationship between the two codes and their actual mechanical causes isn't straightforward. Let me walk through what these codes actually mean and why the diagnosis sequence matters. P0776 is a performance code. It means the TCM commanded Pressure Control Solenoid B to a specific position and the expected hydraulic response — confirmed by shift ratio data and pressure circuit feedback — did not occur within the tolerance the TCM is calibrated to accept. This code does NOT mean the solenoid is electrically failed. It means the hydraulic result was wrong. The cause can be a failed solenoid, a worn solenoid bore in the valve body, low line pressure preventing the solenoid from achieving the commanded pressure, or degraded fluid altering the hydraulic response characteristics. Four different causes, one code.
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Nissan Solenoid Code AccessEnhanced Nissan/Infiniti TCM access for P0776 and P0778 diagnosis. Live solenoid command data and pressure circuit feedback during a road test shows you whether the TCM is seeing an electrical fault, a performance fault, or both, which directs you to the right diagnosis path without guessing.
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Performance Code Hydraulic TestWhen P0776 is present without P0778, line pressure testing is the mechanical step that determines whether the solenoid performance fault is from the solenoid itself, a worn valve body bore, or a hydraulic supply issue. This test is required before any parts are ordered on a P0776-only diagnosis.
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Note: RE5R05A Uses Nissan Matic FluidThe RE5R05A uses Nissan Matic fluid, not CVT fluid. We're noting this here because Nissan fluid confusion is the service error most likely to contribute to P0776 returns after a fluid service on Nissan transmissions. Always verify fluid spec by model and transmission type before filling.
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