How to Fix P205B Code on Duramax (A Comprehensive Guide)

There are Diagnostic Trouble Codes (DTC) for every problem in your Duramax. These DTCs make it easier for the user to identify the exact problem and take measures accordingly.

The P205B code in your Duramax indicates a problem with the temperature sensors in the reductant tank. PCM sets the code when detecting an abnormal temperature beyond a particular range.

So, are you looking for a solution to this problem? Well, you are in the right place to do so. In this article, we will be covering everything you need to know regarding the P205B code for Duramax and how to resolve it.

P205B Code On Duramax

What Does The P205B Code Mean For Duramax?

Duramax engines are known for their long service life. That does not negate the fact that they are not without flaws.

As stated earlier, The P205B code in your Duramax indicates a problem with the temperature sensors in the reductant tank. PCM sets the code when it detects an abnormal temperature beyond a certain range.

With these sensors out of service, it is evident that your vehicle will show lower performance. That is where the P205B code comes into the catch. The full breakdown of this code has been stated below:

P = Powertrain, the system of components that propels your car forward.

2 = A generic manufacturing code

0 = Refers to an ambient air temperature sensor

5B = This is the problem-specific index (In our case, it refers to the reductant tank temperature sensor circuits)

How Serious Is Code P205B On Duramax?

The P205B is a very severe issue, and you are recommended not to drive your car when the code keeps flashing in your vehicle. If the code flashes suddenly, you should stop driving immediately and repair it as soon as possible.

If left for a long time, this problem can become a serious issue causing the entire system of the car and its engine to fail. Furthermore, driving with the existing problem can prove to be a significant source of a potential car accident.

Additionally, damage can also occur to the catalyst inside the engine, which might potentially cause the fuel economy to decrease,

What Causes P205B Code On Duramax?

Several root problems can cause the P205B code to appear in your Duramax vehicle.

We have compiled and listed some more common reasons that can cause this P205B code to flash in your vehicle.

  • Defective reductant tank temperature sensor
  • Open or short-circuits in the tank can cause malfunctions.
  • Faulty PCM controller
  • Faulty programming codes have been inputted.

How To Fix Code P205B On Duramax?

If you fix the P205B code issue, you will require several diagnostic tools to help you out. Some of the most important ones include a scanner, an ohmmeter, screwdrivers, and other power tools.

Additionally, ensure extra components, including wires, that you will be required to change if the current ones are damaged. Once you have got your hands on all the needed equipment, you can follow the step-by-step procedure below:

Step 1: Diagnosis

Source: obdnerdz

First, you will need to diagnose and find the exact root cause of the issue. You can test the various associated components to their maximum parameter.

Start with testing the reductant temperature sensor. If the maximum amount cannot be reached, there is a problem with the components associated with that same feature.

You can also use a diagnostic scanner or DVOM to find problems with the input and output circuits of the temperature sensors.

Step 2: Repair Modules

In most cases, the fault might lie in the engine module. If the associated modules malfunction, the tank temperature sensors will act up. All you need to do is repair the modules, log into the system, and re-program it.

Step 3: Replace Fuel Injector

The fuel injector is another core component associated with temperature functions. If your fuel injector breaks, you might need to replace it with a new one.

Use your power tools and screwdrivers to open the latches and screws and install a new fuel injector in the place of the old one.

Step 4: Fix ECU

Source: ColinOFlynn

While not so common, the ECU can often cause this code to be also issued. To fix it, simply replace the ECU. Since nothing is wrong with the sensors in the first place, the code should stop flashing.

Other symptoms of getting the P205B Code on Duramax

If you have the P205B code flashing in your car, there are several symptoms you might notice along with it. Some of the more common problems associated with the code are as follows:

  • Service Engine Light Flashed Continuously.
  • Engine Performance declines over time.
  • Black smoke might come out of the exhaust of your vehicle.
  • Decrease  in fuel efficiency

How Much Does It Cost To Fix Duramax P205B Code?

The typical cost of fixing the P205B code on your Duramax will depend on whether you will do it yourself or hire a professional to help out.

If you hire a professional, you will be required to pay a labor cost for it. The average labor cost for a single hour is usually about 75 to 150 USD.

Furthermore, you will need to account for replacing certain parts and components, which could prove very expensive. For instance, if you need to replace the ECM module, this will set you back by around 800 USD.

On the other hand, if you need to replace specific sensors or wires, they will only cost around 50-100 USD or even lower.

Can You Drive Your Duramax With Code P205B?

You can drive your Duramax even if the P205B code keeps flashing. This is because the temperature sensors do not have any effect on the way you drive.

However, the vehicle’s standard performance will depreciate as the fuel economy decreases. So do expect a lot of throttling and rough driving.

Additionally, if the code keeps flashing, it can be very annoying and distracting for the driver in the long run.


Nothing beats driving a car at the peak of its performance. While Duramax is known for its smooth rides, they are prone to various problems identified by its codes.

While you can choose to fix the issue by yourself, we advise you against this. This is because there are a lot of technicalities associated with repairing or replacing various components of the engine.

If you are not careful, you can even get shocked. So, if you are going to take the risk, ensure you are well-prepared if things go south!

Similar Posts