Technical Description of OBD-II Trouble Code
The circuit for the Evaporative Emissions (EVAP) Fuel Vapor Temperature Sensor is experiencing intermittent issues.
What does that mean?
This is a generic diagnostic trouble code (DTC) that applies to OBD-II vehicles, including those from Mercedes Benz, VW, Audi, Subaru, Chevy, Dodge, BMW, Suzuki, Hyundai, Sprinter, etc. However, it is more commonly found on Mercedes-Benz vehicles.
The EVAP system was implemented in vehicles for various reasons, such as reducing emissions, improving fuel efficiency, and containing fuel vapors that would otherwise go to waste. Additionally, it efficiently recycles unused fuel.
To maintain desired emissions, the EVAP system relies on multiple sensors, switches, and valves that are monitored and adjusted by the Engine Control Module (ECM). The fuel vapor temperature sensor, in particular, helps the ECM monitor the temperature of unburned vapors.
It is worth noting that the EVAP system utilizes plastic components to transport unburned fuel vapors to the engine. However, exposure to harsh weather conditions, especially during winter, can cause these plastic components to crack, split, break, or clog.
When the ECM detects missing electrical values or values outside the specified range in the EVAP fuel vapor temperature sensor or its circuits, it triggers the check engine light and activates codes P2028, P2024, P2025, P2026, and P2027. It is important to prioritize the overall health of the EVAP system in such cases.
Code P2028 is intermittent, meaning it comes and goes.
What is the severity of this DTC?
On the severity scale, this EVAP fault is considered low. The primary purpose of the EVAP system is to reduce emissions, and there are no significant safety risks associated with this fault. However, it is crucial to address the issue promptly to prevent further problems.
What are some of the symptoms of the code?
Symptoms of a P2028 trouble code may include:
What are some of the common causes of the code?
Possible causes of this P2028 fuel trim code include:
How do I troubleshoot and repair a P2028 code?
As mentioned earlier, it is crucial to ensure the overall health of the EVAP system. Check for obstructions and visible cracks in the plastic pipes. Locate the source of fresh atmospheric air that enters the EVAP system to regulate pressure differences. In most cases, the system’s components are located underneath the vehicle, so using wheel ramps for convenience and safety is recommended.
NOTE: Exercise caution when disconnecting or manipulating EVAP pipes and hoses, as they may appear healthy but can break during disconnection. This may require replacement or repair before further diagnostics can be performed.
Test the sensor by performing a pin-out test to verify its functionality, as the ECM relies on voltage readings from the EVAP fuel vapor temperature sensor to monitor temperatures.
