P0128
DTC P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)HINT: This is the procedure of "thermostat" malfunction detection.
CIRCUIT DESCRIPTION
DTC Detecting Condition:
If the engine coolant temperature (ECT) does not reach 75°C (167°F) despite sufficient warm - up time has elapsed.
MONITOR DESCRIPTION
Monitor Strategy:
Typical Enabling Conditions:
Typical Malfunction Thresholds:
Component Operating Range:
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 (Engine Coolant Temperature). When the estimated coolant temperature reaches 75°C (167°F), the ECM checks the actual ECT. If the actual ECT is less than 75°C (167°F), the ECM will interpret this as a fault in the thermostat or engine cooling system and set a DTC.
MONITOR RESULT (MODE 06 DATA)
Refer to "Monitors, Trips and/or Drive Cycle" for detailed information.
The test value and test limit information are described as shown in the 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.
- TID (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.
INSPECTION PROCEDURE
Step 1 - 2:
Step 3:
HINT: Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. 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, as well as other data from the time when a malfunction occurred.