Thermostat Monitor

OBD System Description - Thermostat Monitor

Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature
DTC
P0128 Refer to DTC P0128: ECT Below Thermostat Regulating Temperature. P0128

MONITOR STRATEGY DESCRIPTION
Detects a stuck open thermostat, using an ECT model vs. measured ECT.

MALFUNCTION CRITERIA AND THRESHOLD VALUE(S)
ECT has not been greater than 84.75 degrees C
And
ECT model > 84.75 degrees C
ECT measurement < 76.5 degrees C
IAT deviation > -20.25 degrees C
"Trailing throttle fuel cut-off" activation time in percent since engine start < 19.92%
Or
"Minimum load" time in percent since engine start < 50%
Or
"Maximum vehicle speed" time in percent since engine start < 90.2343%
- Fail Time > 2,000 ms

SECONDARY PARAMETERS AND ENABLE CONDITIONS
Disable Conditions:
- ECT fault
- MAF sensor fault
- IAT sensor fault
- MAF/TP sensor plausibility fault
- Crank senor fault
- ECT at start < -9.75 degrees C
- ECT at start > 54.75 degrees C
- IAT at engine start < -9.75 degrees C

TIME LENGTH AND FREQUENCY
Recurrence rate: 1,000 ms