Many drivers tend to ignore codes that cause the Check Engine light to illuminate when there are no obvious symptoms. The issue with that tactic is that the check engine light is capable of informing you that there is a problem – it doesn’t tell you how many faults the ECM/PCM has identified – unless there’s an actual one.
Therefore, if you stop by the detail shop or use your own detector and, for instance, receive a P0128 code, you might think, “I’ll start taking care of that later,” but when “later” finally comes, you find that you have approximately five or six additional issues that have accumulated behind the original issue that lit up the check engine light.
What Does Code P0128 Mean?
Code P0128 is a generic OBD-II trouble code that indicates a problem with the engine’s coolant temperature being below the thermostat regulating temperature for too long. Specifically, it means that the engine coolant temperature sensor has detected that its coolant temperature has not reached the correct operating temperature within a specified time after starting the engine.
The typical operating temperature for an engine is between 195 and 220 degrees Fahrenheit (90 to 105 degrees Celsius). If the engine fails to reach this temperature within a specific time, the code P0128 will be triggered.
What Are the Causes of the P0128 Code?
The P0128 code occurs because of one or more of the following issues:
Malfunctioning Thermostat:
A faulty thermostat can prevent the engine from reaching its average operating temperature, triggering the P0128 code.
Faulty Engine Coolant Temperature (ECT) Sensor:
The ECT sensor measures the engine coolant temperature and sends the information to the engine control module (ECM). Also, If the ECT sensor is faulty or sends an incorrect signal, the ECM may think the engine is not warming up properly and trigger the P0128 code.
Low Engine Coolant Level:
A low engine coolant level can cause the engine to overheat or not reach its average operating temperature, triggering the P0128 code.
Failed Engine Cooling System:
A failed engine cooling system, including a failed water pump, radiator, or cooling fan. However, it can prevent the engine from reaching its average operating temperature and cause the generation of the P0128 code.
Faulty Thermostat Housing:
In some cases, a faulty thermostat housing can cause the thermostat to malfunction, leading to the P0128 code.
Faulty Engine Control Module:
In rare cases, a faulty ECM may cause the P0128 code.
However, it is essential to have the cause of the P0128 code adequately diagnosed and repaired to ensure that the engine is running at its optimal temperature, which can help prevent damage to engine components and reduce emissions.
What Are the Symptoms of P0128 Codes?
The symptoms of a P0128 code may vary depending on the severity of the issue and the type of vehicle. Some common symptoms associated with this code include:
Check Engine Light:
The most common symptom associated with a P0128 code is the illumination of the check engine light on the dashboard.
Poor Fuel Economy:
When the engine is running more relaxed than usual, it may cause the fuel mixture to be too rich, resulting in poor fuel economy.
Reduced Engine Performance:
An engine not operating at the optimal temperature may not perform as well as it should. It may result in reduced power and acceleration.
Engine Overheating:
While it may seem counterintuitive, a P0128 code can sometimes occur due to engine overheating. It happens if the thermostat is stuck in the open position, allowing the coolant to flow freely through the engine and not properly regulating the temperature.
Reduced Heater Output:
A malfunctioning thermostat can also affect the operation of the vehicle’s heater, resulting in reduced output of warm air.
How to Fix the P0128 code?
The steps to fix a P0128 code will depend on the underlying cause of the issue. Here are some common steps that may help to improve the code:
Replace the Thermostat:
If the thermostat is faulty, it may need replacement. Well, it is relatively simple to repair with the help of a qualified mechanic or even a DIY enthusiast with some mechanical experience.
Replace the Engine Coolant Temperature Sensor:
If the ECT sensor is found to be faulty or sending incorrect readings, it may need to be replaced. It is also a relatively simple repair that a qualified mechanic or DIY enthusiast can do.
Check Engine Coolant Level:
Ensure the engine coolant level is sufficient, top off the coolant if needed. And also check for leaks in the cooling system.
Check and Repair the Engine Cooling System:
If there are any issues with the engine cooling system, such as a failed water pump, radiator, or cooling fan, these components may need to be repaired or replaced.
Check and Repair the Thermostat Housing:
If the thermostat housing is found to be faulty, it may need to be replaced to ensure proper thermostat operation.
Check and Replace the Engine Control Module:
In rare cases, a faulty ECM may cause the P0128 code. If this is the case, the ECM may need to be replaced or reprogrammed.
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How Much Does it Cost to Fix the P0128 code?
The cost to fix a P0128 code will vary depending on the issue’s underlying cause and the vehicle’s make and model. Here are some rough estimates of the cost for different repairs:
Thermostat Replacement:
The cost for a thermostat replacement can range from $100 to $300, depending on the make and model of the vehicle and the labor rates at the repair shop.
Engine Coolant Temperature Sensor Replacement:
The cost for a sensor replacement can range from $50 to $200. While it depends on the make and model of the vehicle and the labor rates at the repair shop.
Engine Cooling System Repair:
Also, the cost for a cooling system repair can range from $100 to $1,000 or more, depending on the extent of the damage and the parts that need to be replaced.
Thermostat Housing Replacement:
The cost for a thermostat housing replacement can range from $100 to $500, depending on the make and model of the vehicle and the labor rates at the repair shop.
Engine Control Module Replacement:
The cost for an ECM replacement can range from $500 to $1,500 or more. Depending on the make and model of the vehicle and the labor rates at the repair shop.
FAQs
A P0128 code is a diagnostic trouble code that indicates that the engine coolant temperature is below the expected range for a specified period.
A P0128 code can be caused by a faulty thermostat, a malfunctioning engine coolant temperature sensor, damaged wiring or connection in the coolant temperature circuit, or a low coolant level.
Symptoms of a P0128 code may include a check engine light, poor fuel economy, reduced engine performance, engine overheating, and reduced heater output.
It is generally safe to drive the vehicle with a P0128 code. Still, it is good to address the issue promptly to prevent potential damage to the engine and to maintain optimal engine performance.
A qualified mechanic will typically use an OBD-II scanner to read the code and perform further diagnostics to determine the underlying cause of the issue.
The steps to fix a P0128 code will depend on the underlying cause of the issue, but common repairs include replacing the thermostat. Replacing the engine coolant temperature sensor, repairing the engine cooling system, and checking and repairing the thermostat housing.
The cost to fix a P0128 code will depend on the underlying cause of the issue and the make and model of the vehicle. But also repairs can range from $100 to $1,500 or more. It is best to have a qualified mechanic diagnose the issue and provide an accurate estimate for the repair
