DTC Advanced Diagnostics: P0128 (2.0L Engine) (2024 2025)
DTC P0128 : Cooling System Malfunction
General Description
The powertrain control module (PCM) monitors the temperatures before and after the thermostat to diagnose whether it is sticking in open position. If the coolant temperature after the thermostat is a specified value, the PCM detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Once per driving cycle |
| Sequence | None |
| Duration | 0.5 seconds or more |
| DTC Type | Two drive cycles, MIL on |
Enable Conditions
Precondition for warm-up diagnosis and permanent diagnosis
| Condition | Minimum | Maximum |
|---|---|---|
| Elapsed time after starting the engine | 4.96 seconds | - |
| Engine coolant temperature (at engine) [ECT Sensor 1] | - | 121.92 deg.F (49.96 deg.C) |
[ ]: HDS Parameter
Warm-up diagnosis
| Condition | Minimum | Maximum |
|---|---|---|
| Engine coolant temperature (at engine) increase since engine start | 36 deg.F (20 deg.C) to 72 deg.F (40 deg.C) | - |
| State of the engine | At idle | |
Permanent diagnosis
| Condition | Minimum | Maximum |
|---|---|---|
| Initial engine coolant temperature (at engine) [ECT Sensor 1] | - | 121.92 deg.F (49.96 deg.C) |
| Engine coolant temperature (at engine) [ECT Sensor 1] | 165.13 deg.F (73.96 deg.C) | - |
Malfunction Threshold
Either of the conditions is met:
- Warm-up diagnosis
The ECT sensor 2 output temperature is less than 165.12 deg.F (73.96 deg.C).
- Permanent diagnosis
The difference between the ECT sensor 1 output temperature and the minimum ECT sensor 1 output temperature is more than 16.2 deg.F (9 deg.C) - 180 deg.F (100 deg.C)*.
*: Depending on engine coolant temperature (at radiator)
Possible Cause
The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
- Thermostat failure
Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC, the freeze data, and the on-board snapshot are stored.
Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, the freeze data, and the on-board snapshot can be cleared with the scan tool clear command.