An Engine Coolant Temperature Sensor (ECTS) monitors the temperature of the coolant. This input is used by the PCM for engine control and as an enabling criteria for related diagnostics. The air flow coming into the engine is accumulated and used to determine if the engine has been driven within conditions that would allow the engine coolant to heat up normally to the thermostat regulating temperature. If the coolant temperature does not reach regulating temperature of the thermostat, diagnostics that use engine coolant temperature as enabling criteria, may not run when expected.
This DTC will set when there has been excessive time to reach a minimum coolant temperature required for closed loop fuel control.
The purpose of this diagnosis is to monitor the minimum coolant temperature that enables lambda closed loop control after start. Minimum coolant temperature to run lambda control must be reached before the threshold time predetermined according to intake air temperature at start. If the lambda control is not active because of low engine coolant temperature within predetermined minimum time after start, the PCM sets DTC P0125
Item
Detecting Condition
Possible Cause
DTC Strategy
Coolant temperature too low for Lambda regulation
Faulty cooling system
Faulty ECT sensor
Enable Conditions
Minimum time(-15? : approx.200sec, -10? : approx.150sec, -4? : 100sec.,25? : 40sec.) after start versus coolant temperature at Start
No relevant failure
6V< Battery voltage <16V
Threshold Value
Lambda control not active when modelled coolant temp. > minimum coolant temp. for Lambda regulation
Diagnostic Time
Immediate
Mil On Condition
2 Driving Cycles
Temp.(?)
Resistance(?)
-20
14.1 ~ 16.8
40
Approx. 1.2
0
Approx. 5.8
60
Approx. 0.6
20
2.3 ~ 2.6
80
Approx. 0.3
THERMOSTAT
Normal Parameter
Valve Opening Temp
80~84?
Valve Closing Temp.
77?
Full Open Lift
Approx. 8mm(95?)