P0128

DTC P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

DESCRIPTION

DTC Detection Condition:

This DTC is set when the Engine Coolant Temperature (ECT) does not reach 75 degree C (167 degree F) despite sufficient engine warm-up time.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

The ECM estimates the ECT based on the starting temperature, engine loads, and engine speeds. The ECM then compares the estimated temperature with the actual ECT. When the estimated ECT 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 interprets this as a malfunction in the thermostat or the engine cooling system and sets the DTC.

MONITOR RESULT




Refer to CHECKING MONITOR STATUS. Checking Monitor Status

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 (refer to "Confirmation Monitor").
- MID (Monitor Identification Date) is assigned to each emission-related component.
- TID (Test Identification Date) is assigned to each emission-related component.
- Scaling is used to calculate the test value indicated on generic OBD II scan tools.

If the Test Value is less than Test Limit when the engine is warmed up, the ECM interprets this as a malfunction.

Step 1-2:

INSPECTION PROCEDURE

HINT: Read freeze frame data using the intelligent tester. 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.