Diagnostic Aids
WARNING: This page is about a different car, the 2002 Isuzu Trooper. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0125 indicates a faulty ECT sensor. Comparing engine coolant temperature displayed on scan tool with actual temperature as measured with a thermometer may aid in diagnosis. If displayed temperature is not close to actual temperature, replace ECT sensor. An intermittent problem can be caused by:
- ECT shares a common ground with transmission fluid temperature, fuel tank pressure and MAP sensors. If DTCs related to these sensors are stored, check ground point.
- Misrouted harness, rubbed-through wire insulation or broken wire inside insulation.
- Poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage.
- If no obvious problem with harness is found, use scan tool to monitor ECT parameter while moving harness connectors and wiring harness. A change in display indicates source of fault.