DTC P0125: Insufficient Coolant Temperature for Closed Loop Fuel Control

CIRCUIT OPERATION
• 5-volt voltage is applied to the engine coolant temperature sensor output terminal (terminal No. 1) from the PCM (terminal No. 44) via the resistor in the PCM. The ground terminal (terminal No. 2) is grounded with PCM (terminal No. 57).
• The engine coolant temperature sensor is a negative temperature coefficient type of resistor. It has the characteristic that when the engine coolant temperature rises the resistor decreases.
• The engine coolant temperature sensor output voltage increases when the resistor increases and decreases when the resistor decreases.
TECHNICAL DESCRIPTION
• The engine coolant temperature sensor converts the engine coolant temperature to a voltage and output it.
• The PCM checks whether this voltage is within a specified range.
DESCRIPTIONS OF MONITOR METHODS
• Engine coolant temperature sensor output voltage drops from over 40°C (104°F) to under 40°C (104°F) and keeps under 40°C (104°F) for 5 minutes.
• Engine coolant temperature sensor output voltage does not reach close loop enable temperature within specified period when engine coolant temperature sensor output voltage at engine start is under 7°C (45°F).
MONITOR EXECUTION
Continuous
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
• Not applicable

Sensor (The sensor below is determined to be normal)
• Volume airflow sensor
• Engine coolant temperature sensor
• Intake air temperature sensor
DTC SET CONDITIONS <Range/Performance problem-drift> Logic Flow Chart


Check Conditions, Judgement Criteria
• Engine coolant temperature decreases from higher than 40°C (104°F) to lower than 40°C (104°F).
• Then the engine coolant temperature has continued to be 40°C (104°F) or lower for 5 minutes.
DTC SET CONDITIONS <Range/Performance problem-low input (time to reach closed loop temperature)> Logic Flow Chart


Check Conditions, Judgement Criteria
• About 60 - 300 seconds have passed for the engine coolant temperature to rise to about 7°C (45°F) after starting sequence was completed.
• However, time is not counted when fuel is shut off.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 6 - Other Monitor .
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:
• Engine coolant temperature sensor failed.
• Harness damage in engine coolant temperature sensor circuit, or connector damage.
• PCM failed.