P23C5: coolant bypass valve C digital position signal high

P23C5 is the high-side range check of the coolant bypass valve C position signal. In this GM strategy the input is a SENT digital value, and the printed failure threshold is above 4,050 counts. “High” is therefore a diagnostic data-range condition, not a statement that coolant temperature or pressure is excessive.

The communication qualifier

SENT communication must remain free of its communication error for this test to be accepted. The controller interprets an out-of-range reported position as a short-to-power condition in the signal circuit. A complete loss of SENT reporting answers a different diagnostic question.

The engine must not be cranking, run/crank must be valid and the diagnostic system must be enabled. Reporting requires four seconds within a five-second window and is Type B, two trips.

What to retain and verify

Keep the digital position value and communication status from the event. Converting 4,050 counts directly into a terminal-voltage specification would require information this table does not provide. A valve-motion command also does not prove that position feedback remained in range. Confirmation should include valid communication and a completed position-range check after diagnosis. Component location, electrical probing details and the decision between circuit repair and assembly replacement require the exact vehicle's service procedure.

Source and application limits

This explanation covers the cited 2025 GM monitor. Confirm the vehicle and calibration in its service information before applying these limits; inclusion in this file does not establish model compatibility. GM diagnostic parameters, PDF page 820.