DTC P0125 - Insufficient Coolant Temperature For Closed Loop

Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
If any Engine Coolant Temperature (ECT) DTCs are set, see appropriate DTC test. If no DTCs are set, go to next step.
Allow engine to cool. Ensure coolant level is full. If coolant level is okay, go to next step. If coolant level is low, check cooling system for leaks. Repair as necessary. Retest system.
Start engine and let idle. Observe ENG COOL TEMP parameter on scan tool. If display increases to greater than 70°F (21°C) within 2 minutes, check for an intermittent problem. See TESTS W/O CODES article. If display is not as specified, go to next step.
Check thermostat for proper operation. Replace thermostat if necessary. Retest system. If thermostat is okay, go to next step.
Using a thermometer, check temperature of water in radiator. Compare reading with display on scan tool. If readings are fairly close, check for sticking thermostat or incorrect thermostat application. Repair as necessary. If display readings are not close, go to next step.

Turn ignition off. Disconnect PCM harness connectors. Using an ohmmeter, measure resistance between ECT sensor signal circuit and ECT sensor ground circuit at PCM harness connector. Compare resistance reading with coolant temperature. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE . If readings are as specified, replace PCM. Retest system. If readings are not as specified, go to next step.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE

Temperature - °F (°C)	Ohms
-40 (-40)	100,700
-22 (-30)	52,700
5 (-15)	21,450
23 (-5)	12,300
41 (5)	7280
59 (15)	4450
77 (25)	2796
95 (35)	1802
113 (45)	1188
140 (60)	667
176 (80)	332
212 (100)	177

Using an ohmmeter, check for high resistance in ECT sensor signal circuit or sensor ground circuit. Check for poor connections at PCM and ECT sensor. Repair as necessary. If ECT sensor circuit is okay, replace ECT sensor. Retest system.