P0128

DTC P0128 Thermostat Malfunction

DESCRIPTION

DTC Detection Conditions:

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

This DTC is output when the Engine Coolant Temperature (ECT) does not reach 75 degrees C (167 degrees F) despite sufficient engine warm-up time.
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 degrees C (167 degrees F), the ECM checks the actual ECT. If the actual ECT is less than 75 degrees C (167 degrees F), the ECM will interpret this as a fault in the engine cooling system or thermostat and set a DTC.

MONITOR RESULT




Refer to detailed information. Checking Monitor Status

The test value and test limit information are described as shown in the following table. Check the monitor result and test values after performing the monitor drive pattern (refer to "Confirmation Monitor").
- Monitor Identification Data (MID) is assigned to each emissions-related component.
- Test Identification Data (TID) is assigned to each test value.
- Scaling is used to calculate the test value indicated on generic OBD II scan tools.

Wiring Diagram:

Step 1-2:

Step 2(Continued)-3:

INSPECTION PROCEDURE

HINT: Read freeze frame data using the intelligent tester. 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, and other data from the time the malfunction occurred.