P0128 – Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
Introduction
Encountering the P0128 code in your Haval? Here is a complete guide to its causes, symptoms, and solutions.
The **P0128 error** is often linked to a malfunctioning coolant thermostat, which may cause the engine to run rich, leading to decreased fuel efficiency and potentially damaging the catalytic converter. The severity level of this code is moderate, and the urgency of repair is soon, as driving with this code for an extended period can lead to more severe issues. **Fixing the P0128 code** requires a thorough diagnosis to determine the root cause of the problem.
WHAT DOES CODE P0128 MEAN
The P0128 trouble code indicates that the coolant temperature is below the thermostat’s regulating temperature, which may be associated with a faulty thermostat, a malfunctioning coolant temperature sensor, or a problem with the engine’s cooling system. This code affects the engine’s performance, as it may cause the engine to run rich, leading to decreased fuel efficiency and potentially damaging the catalytic converter. The P0128 code is often linked to issues with the engine’s cooling system, which can be caused by a variety of factors, including a faulty thermostat, a malfunctioning coolant temperature sensor, or a problem with the engine’s cooling system.
COMMON Haval MODELS AFFECTED
The P0128 code can affect various Haval models, including:
- Haval H6
- Haval H9
- Haval F7
- Haval F5
- Haval Jolion
SYMPTOMS TABLE
The following symptoms may be associated with the P0128 code:
| Symptom | Frequency of Occurrence |
|---|---|
| Decreased fuel efficiency | High |
| Engine running rich | Medium |
| Coolant temperature gauge reading lower than normal | Medium |
| Engine stalling or hesitation | Low |
| Check Engine Light illumination | High |
| Engine knocking or pinging | Individual |
| Increased emissions | Medium |
CAUSES TABLE
The following causes may be associated with the P0128 code:
| Potential Cause | Probability |
|---|---|
| Faulty coolant thermostat | High |
| Malfunctioning coolant temperature sensor | Medium |
| Problem with the engine’s cooling system | Medium |
| Wiring issue with the coolant temperature sensor circuit | Low |
| ECU logic issue | Low |
REAL-WORLD DRIVING SCENARIOS
When driving with the P0128 code, the driver may experience decreased fuel efficiency, engine running rich, and coolant temperature gauge reading lower than normal. The issue may be more pronounced during cold start, acceleration, or highway driving. The driver may also notice engine stalling or hesitation, especially when the engine is under load.
DIAGNOSTIC STEPS
To diagnose the P0128 code, the following steps can be taken:
IF the coolant temperature gauge reading is lower than normal, THEN check the coolant thermostat for proper operation.
IF the coolant temperature sensor is malfunctioning, THEN check the sensor’s wiring and circuit for any issues.
IF the engine’s cooling system is malfunctioning, THEN check the system for any leaks or blockages.
COMMON DIAGNOSTIC MISTAKES
The following diagnostic mistakes can be made when diagnosing the P0128 code:
Replacing the coolant temperature sensor without checking the wiring and circuit.
Not checking the coolant thermostat for proper operation.
Not inspecting the engine’s cooling system for any leaks or blockages.
Assuming the issue is with the ECU logic without checking the sensor and thermostat.
WHEN NOT TO REPLACE THE SENSOR
Replacing the coolant temperature sensor may not solve the issue if the problem is with the wiring or circuit, or if the ECU logic is faulty. In such cases, replacing the sensor will not fix the issue, and further diagnosis is required to determine the root cause of the problem.
HOW TO FIX
To fix the P0128 code, the following steps can be taken:
Replace the faulty coolant thermostat.
Repair or replace the malfunctioning coolant temperature sensor.
Fix any issues with the engine’s cooling system.
Update the ECU software if necessary.
SEVERITY LEVEL
The severity level of the P0128 code is moderate, and the urgency of repair is soon. Driving with this code for an extended period can lead to more severe issues, such as engine damage or increased emissions. The driving risk is medium, and the engine impact is significant, as the issue can cause the engine to run rich, leading to decreased fuel efficiency and potentially damaging the catalytic converter.
IS IT SAFE TO DRIVE WITH THIS CODE
It is not recommended to drive with the P0128 code for an extended period, as it can lead to more severe issues. However, if the issue is minor, and the engine is not showing any significant symptoms, it may be safe to drive for a short period. Nevertheless, it is essential to address the issue as soon as possible to avoid any further damage.
ESTIMATED REPAIR COST
The estimated repair cost for the P0128 code can range from $200 to $1,000, depending on the root cause of the issue and the complexity of the repair.
PREVENTIVE MAINTENANCE TIPS
To prevent the P0128 code, regular maintenance is essential. This includes checking the coolant level and condition, inspecting the engine’s cooling system for any leaks or blockages, and replacing the coolant thermostat and temperature sensor as recommended by the manufacturer.
In my experience, the P0128 code is often linked to a faulty coolant thermostat. However, it is essential to perform a thorough diagnosis to determine the root cause of the issue, as replacing the thermostat may not solve the problem if the issue is with the sensor or ECU logic.
TOOLS REQUIRED FOR DIAGNOSTICS
The following tools are required for diagnosing the P0128 code:
- Scan tool
- Multimeter
- Thermometer
- Coolant pressure test kit
- Wiring diagram
TECHNICAL REFERENCE VALUES
The following technical reference values are relevant for diagnosing the P0128 code:
| Parameter | Normal Range | Fault Indication Behavior |
|---|---|---|
| Coolant temperature | 180-200°F | Lower than normal |
| Engine running rich | Not applicable | Higher than normal |
18. FAQ
What does code P0128 mean?
The P0128 code indicates that the coolant temperature is below the thermostat’s regulating temperature, which may be associated with a faulty thermostat, a malfunctioning coolant temperature sensor, or a problem with the engine’s cooling system. The **P0128 trouble code** is often linked to issues with the engine’s cooling system, which can be caused by a variety of factors. **Diagnosing the P0128 code** requires a thorough diagnosis to determine the root cause of the issue.
Is it safe to drive with code P0128?
It is not recommended to drive with the **P0128 error** for an extended period, as it can lead to more severe issues. However, if the issue is minor, and the engine is not showing any significant symptoms, it may be safe to drive for a short period. Nevertheless, it is essential to address the issue as soon as possible to avoid any further damage. **Fixing the P0128 code** is crucial to prevent any further damage to the engine.
Will the code clear itself?
The **Haval P0128** code will not clear itself, and it requires a thorough diagnosis to determine the root cause of the issue. The code can be cleared using a scan tool, but if the underlying issue is not addressed, the code will return.
Does the sensor need replacement?
The coolant temperature sensor may need replacement if it is malfunctioning. However, replacing the sensor without checking the wiring and circuit may not solve the issue. **Diagnosing the P0128 code** requires a thorough diagnosis to determine the root cause of the issue.
How much does it cost to fix?
The estimated repair cost for the **P0128 trouble code** can range from $200 to $1,000, depending on the root cause of the issue and the complexity of the repair. **Fixing the P0128 code** requires a thorough diagnosis to determine the root cause of the issue, and the cost of repair will depend on the specific issue.
RELATED TROUBLE CODES
The following trouble codes are related to the P0128 code:
- Error P0123 on Haval — faulty coolant temperature sensor
- Error P0125 on Haval — faulty coolant thermostat
- Error P0133 on Haval — faulty oxygen sensor
- Error P0153 on Haval — faulty oxygen sensor heater