DTC Advanced Diagnostics: P0128: General Description

Courtesy of HONDA, U.S.A., INC.

Courtesy of HONDA, U.S.A., INC.

The abnormality of the thermostat is monitored by engine coolant temperature (ECT) sensor 1 and estimated engine coolant temperature. The estimated engine coolant temperature is calculated from the driving condition. If either of the following condition occurs, the powertrain control module (PCM) detects a malfunction and stores a DTC.

• Malfunction determination 1

  The ECT sensor 1 value is less than a specified value when the estimated engine coolant temperature reaches a certain value.

• Malfunction determination 2

  The estimated engine coolant temperature does not lower from a certain value, and the ECT sensor 1 value is less than a specified value.

Monitor Execution, Sequence, Duration, DTC Type