Maintaining your truck's performance is crucial, and one way to ensure it stays on the road without major hiccups is by understanding and addressing fault codes as they come up. Today, we’re going to break down fault code 3255, also known as SPN 3246 FMI 0 or SPN 3246 FMI 16.
This code signals an issue with the Diesel Particulate Filter (DPF) outlet temperature sensor, which has detected temperatures exceeding the allowable limit. If left unresolved, this can lead to severe damage in your truck’s aftertreatment system. Let’s dive into what this means and how you can fix it.
What Does Fault Code 3255 Mean?
Fault code 3255, or SPN 3246 FMI 0 or FMI 16, indicates that the DPF outlet temperature sensor has recorded temperatures above the safe threshold. This sensor is part of the aftertreatment system, located at the outlet of the DPF, and it plays a vital role in monitoring the exhaust temperature. If this sensor detects a temperature higher than 1355°F (735°C) for more than 145 seconds, the Engine Control Module (ECM) steps in to prevent further damage.
Here’s what happens when this fault code triggers:
- Red stop engine lamp and malfunction indicator lamp (MIL) are disabled.
- Active and stationary regeneration of the DPF is halted.
- Exhaust gas recirculation valve operation is disabled.
- Engine torque is reduced to prevent overheating and system damage.
If the fault persists, the ECM may even shut down the engine if the engine protection shutdown feature is enabled. This fault code is serious, and immediate action is needed.
How the DPF Outlet Temperature Sensor Works
The DPF outlet temperature sensor is part of a smart system that communicates with the ECM through the J1939 data link. It continuously monitors temperatures at both the intake and outlet of the DPF while the engine is running. The diagnostic process runs constantly, except during active DPF regeneration, to ensure the outlet temperature stays within safe limits.
How to Address Fault Code 3255
When you encounter fault code 3255, it's essential to act quickly. Here's how you can clear the fault:
- Perform a key cycle: Turn off the engine, wait for one minute, then restart it.
- Let the engine idle for one minute.
Once this is done, the fault code status on your OTR Diagnostics tool should change to inactive after the diagnostic passes. You can also use OTR Diagnostics to clear the MIL light and check the status of any active or inactive fault codes.
Common Causes of Fault Code 3255
This fault code typically indicates that the DPF outlet temperature has reached unsafe levels. Common reasons for this include:
- Excessive engine oil or diesel fuel entering the exhaust system.
- A malfunctioning DPF outlet temperature sensor.
- A face-plugged diesel oxidation catalyst.
Addressing these issues as soon as possible is critical to avoiding further damage and ensuring compliance with emissions standards.
The Power of OTR Diagnostics
If you’re using OTR Diagnostics, you already have the tools needed to address this issue. OTR Diagnostics allows you to perform OEM fault code resets, conduct aftertreatment maintenance, and initiate regens. For those who don’t have OTR Diagnostics yet, it’s designed to give you full access to your engine’s fault code information, making maintenance easier and more efficient. This tool empowers you to stay ahead of problems before they become costly repairs.
Preventative Maintenance Tips
Addressing fault code 3255 quickly will help you avoid major downtime and expensive repairs. Regular maintenance of your truck’s aftertreatment system and using high-quality diesel exhaust fluid (DEF) are critical steps in preventing issues like this from arising.
For more information on how OTR Diagnostics can help you take control of your truck's maintenance, check out OTR Diagnostics Pro.
Fault code 3255 is a reminder that staying on top of your truck’s performance is essential. By understanding what’s going on behind the scenes and using the right tools, you can keep your truck running smoothly and efficiently, saving you time and money in the long run.
