Diagnostic Aids

WARNING: This page is about a different car, the 2002 Isuzu Rodeo Sport, 2002 Isuzu Rodeo, 2002 Isuzu Axiom, and 2002 Honda Passport. 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.

If DTC cannot be duplicated, reviewing scan tool FAILURE RECORDS data can be useful in determining mileage and frequency of DTC occurrence.