P205B Code: Reductant Tank Temperature Sensor Circuit Range / Performance

The reductant tank temperature sensor measures the amount and temperature of the reductant in the diesel exhaust aftertreatment system. It provides accurate readings for the powertrain control module (PCM). The PCM uses the data as a reference for any adjustments it has to make to various engine and exhaust processes.

If the PCM receives an improbable voltage signal that is higher or lower than the programmed range of the reductant tank temperature sensor, its diagnostics will log a P205B code.

What Does the P205B Code Mean?

Diagnostic trouble code (DTC) P205B indicates “Reductant Tank Temperature Sensor Circuit Range/Performance.”

Modern diesel-engine vehicles rely on their diesel exhaust aftertreatment system to keep their emissions within safe and legal levels. The last stage of the treatment process is called catalytic reduction. It adds diesel exhaust fluid (DEF), which is also known as reductant, to the exhaust stream.

Reductant breaks down the remaining particles of toxic exhaust into safer substances. It can only work when the temperature in the exhaust system is sufficiently hot. The reductant tank temperature sensor takes the level and temperature of the DEF.

The PCM regularly checks the reductant tank temperature sensor. If the computer doesn’t get the right response, it will set the generic powertrain code P205B.

Note: The definition of code P205B can differ depending on the vehicle manufacturer. Check the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P205B Code?

• Bad reductant tank temperature sensor
• Wiring problems in the reductant tank temperature sensor system
• Bad selective catalytic reduction (SCR) controller
• Faulty PCM
• SCR or PCM programming error

What are the Common Symptoms of the P205B Code?

• Illuminated check engine light
• Illuminated diesel exhaust fluid warning light
• Vehicle derated or stuck in “limp” mode
• Vehicle can’t restart after driving with the warning lights illuminated

How to Diagnose the P205B Code

The P205B code is a generic powertrain code that various makes and models can log. However, this does not mean that there is a one-size-fits-all solution to identify its underlying problem.

If you’re not confident about conducting diagnostic tests on your vehicle, it’s a good idea to bring it to a professional mechanic. Otherwise, you can go ahead and diagnose the issue yourself. To help you get started, here is a video that can give you an idea of what the process might involve:

How to Fix the P205B Code

Attempting to fix a P205B code can become a challenging task if you don’t have the right tools and know-how to test the reductant tank temperature sensor. In most cases, it’s best to leave the job to professionals.

But if you have the right tools and knowledge to test and replace your vehicle’s reductant tank temperature sensor, you can address the issue on your own. Make sure you consult a repair manual or an online repair database that’s specific to your vehicle before you get started.