NGC

P0125-INSUFFICIENT COOLANT TEMP FOR CLOSED-LOOP FUEL CONTROL





For a complete wiring diagram Consult Diagrams/Electrical.

Theory of Operation

The engine coolant temperature sensor is a negative temperature coefficient thermistor-type sensor whose resistance varies inversely with temperature. At cold temperatures the sensor resistance is high so the voltage is high. As the coolant temperature increases the resistance decreases and the voltage becomes low. The INSUFFICIENT COOLANT TEMP FOR CLOSED-LOOP FUEL CONTROL determines if the engine coolant temperature will reach the closed loop fueling control temperature limit in a regulated time after start.

- When Monitored:
With the ignition on, battery voltage greater than 10.4 volts, and no ECT sensor circuit DTCs present.

- Set Condition:
The engine temperature does not go above -10° C (15° F). Failure time depends on start-up coolant temperature and ambient temperature. (i.e. 2 minutes for a start temp of -10° C (15° F) or up to 10 minutes for a vehicle with a start-up temp of -28° C (5° F). Two Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.Initial Inspection and Diagnostic Overview

Diagnostic Test

1. CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR OPERATION.

NOTE: Diagnose and repair any engine coolant temperature sensor circuit DTCs before proceeding with this test.

NOTE: Extremely cold ambient temperatures may cause this DTC to set.

Perform the diagnostic procedure for *CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR OPERATION. Checking the Engine Coolant Temperature Sensor Operation

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. Powertrain Verification Test

No

- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. Checking For An Intermittent DTC