P0128
DTC P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)DESCRIPTION
DTC Detection Condition:
This DTC is output when the Engine Coolant Temperature (ECT) does not reach 75 degree C (167 degree F) despite sufficient engine warm-up time.
MONITOR DESCRIPTION
Monitor Description:
Monitor Strategy (Part 1):
Monitor Strategy (Part 2):
Typical Enabling Conditions:
Typical Malfunction Thresholds:
The ECM estimates the coolant temperature based on starting temperature, engine loads, and engine speeds. The ECM then compares the estimated temperature with the actual ECT. When the estimated coolant temperature reaches 75 degree C (167 degree F), the ECM checks the actual ECT. If the actual ECT is less than 75 degree C (167 degree F), the ECM will interpret this as a fault in the thermostat or the engine cooling system and set a DTC.
MONITOR RESULT
Refer to "Checking Monitor Status" for detailed information. Mode 6 Data
The test value and test limit information are described as shown in the given table. Check the monitor result and test values after performing the monitor drive pattern
- TID (Test Identification Data) is assigned to each emissions-related component.
- TLT (Test Limit Type):
If TLT is 0, the component is malfunctioning when the test value is higher than the test limit.
If TLT is 1, the component is malfunctioning when the test value is lower than the test limit.
- CID (Component Identification Data) is assigned to each test value.
- Unit Conversion is used to calculate the test value indicated on generic OBD II scan tools.
Step 1-2:
INSPECTION PROCEDURE
HINT: Read freeze frame data using the intelligent tester or the OBD II scan tool. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.