Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 1997 GMC Yukon, 1997 GMC Suburban, 1997 GMC Pickup, 1997 GMC Cab & Chassis, and 1997 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
When DTC P0125 is set, ECT sensor is skewed or engine thermostat does not operate properly. An intermittent may be caused by a poor connection, rubbed through wire insulation or a broken wire inside insulation. Inspect VCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness. If connections and harness are okay, observe scan tool connected between VCM connector terminals while wiggling related connectors and wiring harness. A change in display will indicate location of fault.