P0808: Clutch-position signal exceeds its valid electrical range

P0808 is the high-direction clutch-position circuit check in GM's GMDAT table. It detects a continuous short-to-high condition when the signal exceeds 95 percent of the reference voltage. This is an electrical range decision, not a direct judgment that the pedal is physically fully applied.

A high signal needs a valid reference

The monitor excludes the specified reference-voltage fault. That dependency matters when several sensor-related codes appear together: the pedal signal cannot be interpreted independently of the supply against which it is measured.

The source uses 200 failing observations in a 250-sample window at a 25-millisecond loop rate. It also requires the engine not to be cranking and system voltage above the documented minimum. Those qualifications separate persistent signal trouble from an observation during a power transition.

Do not confuse voltage limits with learning

The adjacent P080A entry checks whether the fully applied pedal position has been learned. A missing learned value and an electrically high input are different conditions. Performing a learning procedure cannot be assumed to repair a circuit that remains outside its valid range.

Use the exact vehicle's sensor and wiring procedure to identify the source of the high signal. Verification should establish valid electrical behavior before any required learning or performance checks are judged. An empty code list immediately after clearing does not show that the high-input monitor has completed successfully.

Source and applicability

2009 General Motors diagnostic parameter file 09OBDG01 GMDAT Engine Diagnostics.pdf. Section-specific modules and calibrations; no per-code model or engine applicability established. This explanation describes the documented monitor, not a universal repair procedure.

GM diagnostic parameters, PDF page 45.