P0730: a CVT ratio fails despite reaching control limits

P0730 is incorrect gear ratio, but the cited TCM implementation is explicitly CVT specific. It compares primary-to-secondary pulley speed ratio with the requested variator ratio and accumulates error after the control system reaches its limits.

More than a momentary ratio mismatch

The described algorithm requires ratio-control integral and pressure limits to be reached, with ratio error and slip evidence accumulating. The displayed threshold is more than 2,000 error units; it is not a fixed RPM difference or 2,000 seconds of slipping.

Prerequisites include both pulley speeds above 280 rpm, no relevant speed or pressure-control faults, and steady-state operation without a shift or brake application. A ratio difference during an ordinary transient is therefore not automatically equivalent to the monitored failure.

Delay varies with the operating point

The supporting table makes the gross-slip evaluation delay a function of ratio and fluid temperature, with displayed values ranging from 0.75 to two seconds. This helps explain why one stopwatch rule cannot describe every qualifying event.

For diagnosis, preserve requested and measured ratio, pulley speeds and whether control limits were reached. The source says the pattern can indicate primary or secondary pressure-control actuator failure; it does not uniquely identify one solenoid or prove belt damage. Verification should establish successful ratio control and a passing monitor using the exact CVT procedure. Do not apply these pulley-specific thresholds to a conventional geared transmission solely because it stores P0730.

Source and applicability

Documented monitors in gm-2025-03a, model year 2025. These are module/calibration examples; vehicle, engine and transmission applicability must be confirmed independently. GM 2025-03a, page 1110. GM 2025-03a, page 1249.