P0708: transmission range high voltage requires the right PWM convention

P0708 is the high-voltage fault for internal transmission range-sensor circuit A in the cited TCM. It evaluates PWM duty cycle to recognize a short-to-power condition.

Confirm the configured signal interpretation

The direct PWM branch uses duty cycle above 91.190 percent. The table has a separate inverse-voltage branch, so the direct threshold cannot be transferred to every sensor configuration. The fault-detection specification is less than 0.5 ohm between signal and controller power; actual interpretation depends on the configured circuit.

This code is consequently different from a claim that the transmission is stuck in a high gear. The word high describes the circuit signature, not the selected or attained gear ratio.

More than battery voltage enables the test

The source requires battery voltage above 9 volts for more than one second. It also lists availability of an ECM message, an enabled communication check and a vehicle mode that supplies accessory power. Missing prerequisites can prevent a meaningful pass or fail result.

The failure window exceeds 0.9 second within a sample period exceeding 2.25 seconds. Preserve the duty-cycle convention, range data and communication context before interpreting an intermittent event. Verification should demonstrate correct range recognition and a passing enabled high-circuit monitor under the applicable transmission service procedure. The table does not provide a safe bypass, connector pinout or mandatory range-sensor replacement instruction.

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 1092.