How to Troubleshoot & Fix P0128 Jeep Wrangler DTC Code?

When you have to bear those in your vehicle, engine trouble codes are always an issue. Some codes have serious implications, while others are easy to deal with.

P0128 is one of the diagnostic trouble codes in the jeep wrangler that indicates irregular coolant temperatures. And here, we will be covering the causes of the code and how to deal with them. Keep reading to find out more!

What does the P0128 Jeep Wrangler code mean?

The error code P0128 mainly refers to the problem with the engine coolant temperature. 

It is a problem with the engine coolant temperature not reaching the required level for the operation. This issue will persist even after starting your engine on a full scale.

For the Jeep Wrangler, the problem has similar implications to the other vehicles. We have added the code breakdown below to understand the situation better. 

  • P – Powertrain, the system that makes the vehicle move forward
  • 0 – A generic number according to the SAE standard 
  • 1 – Fuel and Air Metering (Coolant Temperature sensor malfunctioning)
  • 28 – Specific Fault Index (Here, the Coolant temperature is recorded below the regulating temperature)

P0128 Code: Causes of Low Coolant Regulating Temperature in your Jeep Wrangler

The OBD-II trouble code P0128 has much to do with the engine’s operating temperature. When the ECM detects anomalies in the engine coolant temperatures, that is where the problem lies. 

Due to such complications, things like decreased fuel economy and higher idles are seen in your Jeep Wrangler. 

That said, some of the prominent reasons behind the sensor not working correctly in the Jeep Wrangler are listed below:

  • Stuck or broken open thermostat
  • Corroded wiring in the coolant temperature circuit
  • Malfunctioning sensor
  • Malfunctioning ECM

Read Also: How To Troubleshoot & Fix P0456 Jeep Wrangler DTC Code?

How to troubleshoot & Fix P0128 Jeep Wrangler code?

The error code P0128 triggers only when the engine’s operating temperature is below 160 F. 

It is a persistent problem of the temperature not going up even after running the engine for 15 minutes. To fix this issue, you may adopt various practices manually. 

But you must remember that there are several anomalies in the engine for which you are detecting the code. Some of the fixes are discussed as follows:

1. Detect and Remove the Code

Before you go for some components replacement, you should attempt to resolve the code by clearing it. For troubleshooting the P0128 code in your Jeep Wrangler, follow the steps as mentioned below:

  • Manage an OBD-II scanner
  • Plug the scanner in the port, which is placed above the pedals on the left side of your Jeep Wrangler
  • Put the key to turn on the vehicle and then press the Read button on the scanner
  • Press on the Erase or Clear button and switch off the vehicle

Clearing the code when the issue is within the PCM will eventually solve the problem. But if this method doesn’t solve your problem, follow the rest of the fixes to get the solution.

Read Also: How to troubleshoot & Fix P06dd Jeep Wrangler DTC Code? [Top 4 Fixes]

2. Inspect the Thermostat to see if faulty or not

Next, The thermostat is a crucial component in a Jeep wrangler engine as it maintains the stable temperature of the engine. 

Isolation of the engine and radiator to ensure that the perfect operating temperature is reached is the primary job of this component. But the trouble increases when the thermostat gets broken or faulty.

Operating temperature is never achieved when the thermostat remains stuck in the engine. That is why the P0128 code becomes predominant, necessitating thermostat replacement. 

We have added the steps you must follow if you want to replace the thermostat and fix the problem yourself. In addition, replace both the upper and lower hoses to ensure the desired outcome. Those steps are:

  • With the help of a 10 mm socket, remove the air intake first
  • Now, unplug the sensor that is associated with the air intake
  • Remove both the upper and lower hoses with the 10 mm socket
  • Carefully take out the old thermostat from its compartment
  • After taking the thermostat out, remove the old gasket and clean that compartment carefully
  • Install the thermostat on the new hoses and ensure perfect fitting
  • Place the new thermostat and make sure that you don’t overtighten the bolts
  • Attach the hose and use clamp pliers to put the clamps in the position
  • After installation, loosen the air bleed valve on the thermostat, drain some fluid, and retighten
  • Reinstall the air intake

When you are done with the process, you need to start the engine for 20 mins and keep it idle. If the problem were from the thermostat, the error code would go. Or else you might want to check out other issues.

Read Also: How to troubleshoot & Fix C121C Jeep DTC Code?

3. Replace the faulty coolant temperature sensor

Since the problem has a lot to do with temperature levels, faulty temperature sensors can sometimes be an issue. So replacing it with a new one is the most viable fix. The process involved in this is discussed below:

  • Put some liquid-type tape sealant on the sensor if it doesn’t have any
  • Now, attach a small hose to the drain plug located in the front of your vehicle
  • Rotate the plug with the pliers in an anti-clockwise direction 
  • Drain the fluid from there and open the radiator cap to help the cause
  • Go down and push on the connector tab and slide it off 
  • Push sideways to let the red tab snap, which will help in the way to access the sensor
  • Use a 19 mm wrench to take out the old sensor and replace it with the new one
  • Snap the red tab down after you are done with the replacement

4. Replace Corroded Wire on Coolant Temperature Sensor

The wires connecting the temperature sensor can get damaged, broken, or corrupted. There is no way to fix them, so you must replace them with new ones.

However, unlike the previous two fixes, replacing the wire is sometimes trickier. Therefore, we suggest you get a mechanic consultation in this regard. At best, replacing the Jeep Wrangler wire would cost around $50-70.

Read Also: How To Troubleshoot & Fix p1494 Jeep DTC Code?


Detecting error codes is always confusing and frustrating if not cleared soon. We have answered a few common queries in this regard that will help you better understand the solutions for P0128.

Can you drive a Jeep Wrangler with the P0128 code?

You can drive your Jeep Wrangler for a while, even after detecting the error code P0128. But you will need to fix it as soon as possible as the engine will become more prone to overheating as time passes.

How much does it cost to fix the Jeep Wrangler P0128 code?

The cost of fixing the P0128 code entirely depends on the root of the problem. Fixing and replacing various parts will cost around $150-200, including labor costs.

Can low coolant result in a P0128 code in a Jeep Wrangler?

Low coolant can cause the detection of error code P0128 because the coolant levels can dictate engine temperatures. When there are low coolant levels in the engine, it will automatically trigger the code.

Final Thoughts

You should mitigate the Coolant temperature not up to the operating level within the month of detection. Or else engine overheating would be a common occurrence, which might lead to engine failure.

Through this article, we tried to give you a comprehensive solution. We hope this will help, and in case of any confusion, let us know.

Read Also: How To Troubleshoot & Fix P1521 Jeep DTC Code?

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