P0747: GR10 C1 clutch stays applied during release

P0747 identifies pressure-control solenoid A stuck on. In the reviewed GM strategy, this means the GR10 C1 clutch appears to retain hydraulic holding capacity after it is commanded to release. The monitor explicitly assumes that the solenoid remains electrically functional.

Low slip can indicate the fault

During a shift, a releasing clutch should develop the expected slip. P0747 watches for C1 slip remaining below 50 rpm in the listed power-down and other-shift cases, or below 100 rpm for a garage shift. This is the opposite of treating all transmission trouble as excessive slip: here, too little slip during release is the important evidence.

Base failure durations differ by shift type: 0.60 second for power downshifts, 0.25 second for garage shifts and 0.150 second for other shifts. Additional offsets and exhaust delays also apply. The C1 closed-throttle downshift support table makes exhaust delay temperature-dependent, so none of those base times should be presented as the complete universal set time.

Interpreting an enabled test

The continuation identifies C1 as the GR10 CB123456R clutch and requires functional speed inputs, enabled driver circuits and suitable hydraulic conditions. Fast learn and solenoid cleaning must be inactive. Relevant circuit, speed and performance faults can inhibit testing.

A meaningful verification records C1 release behavior during an eligible shift with the correct temperature-dependent allowance. Passing an electrical check alone cannot establish hydraulic release. The table supports a hydraulic-performance interpretation, not automatic solenoid replacement or model coverage; transmission-specific service diagnosis is required.

Source: GM monitor, PDF page 2069; GM monitor, PDF page 2070; GM monitor, PDF page 2071; GM monitor, PDF page 2072; GM monitor, PDF page 2074; GM monitor, PDF page 2423.