Known for their rugged power and durability, Ram diesel pickup trucks have been around for a long time.
Cummins diesel models often display the “Service DEF System See Dealer” warning that I have found to be common among mechanics.
The trouble code P203E or P203F is displayed when the OBD scanner is connected to the vehicle (based on the model).
In addition to Jeep models equipped with Cummins diesel engines, this DEF system problem also impacts Wranglers, Gladiators, and Grand Cherokees.
I will outline the most common causes and discuss how to resolve the “Service DEF System” error message using my expertise.
Jeep and Ram diesel engines with Cummins engines are both affected.
We’ll get started right away!
When the “Service DEF System Sees Dealer” alert appears, what should I do?
Diesel Exhaust Fluid is commonly referred to as DEF in layman’s terms. It reduces harmful emissions from your engine through the Diesel Exhaust Fluid System.
DEF is used to convert nitrogen oxides (NOx) into water vapor and harmless nitrogen by injecting a small amount into the exhaust stream.
An issue with the DEF tank or system is detected by the vehicle when the “Service DEF System See Dealer” message appears on your dashboard.
In this article, we will discuss some of the causes of this issue in detail.
See the dealer for DEF system service:
1. Deft tank overfilled
Overfilling the DEF tank is one of the most common causes.
A fluid level sensor can be properly installed in the tank because of the air gap at the top.
DEF level sensors, introduced in the 2019 model, can be damaged by overfilling your Diesel Exhaust Fuel tank.
The Ultrasonic Frequency (UF) signal from an overfilled tank cannot bounce back to the sensor as there is no air space for it to bounce.
What does this mean in simple terms? It’s like trying to get an Internet signal in the dark to get a cell phone signal in a tunnel.
An additional cause could be dirty DEF injectors:
2. Dirty DEF Injectors
Diesel exhaust fluid (DEF) is a fluid that is used to reduce emissions from diesel engines through the use of a special injector.
Deposits and debris can clog this injector over time. The system performance suffers as a result of this restriction of DEF flow.
Filters can become fouled with dirt, minerals, and carbon buildup due to contaminants such as dirt, minerals, and carbon. The system will assume that the DEF tank has a low level if the flow is reduced.
Drivers are prompted to refill the tank by warning lights and codes. Nevertheless, if the injectors are not cleaned, replenishing DEF may not resolve the root problem.
A full resolution of this problem requires a thorough cleaning of the DEF injectors and the removal of any blockages.
3. Residual Ice Buildup
“Service DEF System” alerts are also commonly caused by ice buildup.
It is possible for the DEF tank and components to become iced over in very cold climates if the temperature drops below 12°F.
Diesel Exhaust Fluid freezes because of this, and can even fail to thaw completely after being heated once it has been allowed to thaw.
When the sensor is trying to measure the DEF level in your tank, it can give the alarming error message in case there is still a layer of ice in the tank.
4. Sensor crystallization of DEF
Cold climates require this, so if you live in one, then this is for you
In addition to crystallizing on level sensors, DEF fluid can also accumulate on tank components after prolonged cold exposure.
Your truck’s ability to measure DEF is affected by this frosty layer, which is like the frosty layer in your freezer.
Inaccurate measurements are caused by crystals blocking the sensor.
Therefore, a warning message will appear on the computer indicating that the DEF system needs to be serviced.
5. Low Diesel Exhaust Fluid
It is also possible for the fluid level to have dropped too low, resulting in the “Service DEF System See Dealer” warning.
In order for the diesel exhaust fluid (DEF) system to function correctly, the DEF tank needs to be adequately topped off.
Leaks can occur when the recommended maintenance schedule is not followed, which leads to failure to top up the fluid.
Over time, DEF deteriorates and needs to be replenished. A driver’s habits and driving conditions can determine the interval.
- Driving aggressively
- Towing frequently
- Towing heavy loads
- Temperatures that are extreme
DEF consumption can be accelerated. It is possible to run out of fuel if the tank is ignored long enough.
Sensor readings are drastically skewed as a result.
The warning light turns on when the DEF reaches an extremely low level.
Refer to Dealer Message for Guide on Fixing and Resetting the DEF System
We will now discuss in more detail how to fix and reset this error message now that we know what the main causes are.
The following recommendations are based on the main cause.
- Overfilled DEF Tank: Remove excessive fluid until the tank reaches the proper level. By doing so, the sensor’s air gap is restored.
- Dirty DEF injector: Make sure the injector is removed and thoroughly cleaned
- Residual Ice Buildup: Thaw your DEF tank completely to avoid residual ice buildup. In order to keep your truck safe and warm overnight, you should keep it in a garage or other warm place. The fluid may need to be drained and traces of ice removed if there is stubborn ice.
- DEF Crystallization: Dissolving crystals within the tank and components can be accomplished by flushing them with distilled water or DEF.
- Low DEF Fluid: Fill to proper level with DEF.
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Clearing and resetting the service DEF system message:
After identifying the issue and correcting it, drive your truck under the following conditions to reset the message:
To reduce fluid movement in the DEF tank, maintain highway speeds for at least 15 minutes. There should be a temperature difference between the DEF tank and the ambient temperature of more than 4°C (39°F).
