Volvo VNL Semi Truck & Volvo D13, Cummins ISX etc. Engine FAQs

Here are some common causes of inaccurate or erratic DEF level gauge readings on a Volvo VNL truck with a Volvo D13 engine: Low DEF fluid level: This may seem obvious, but if you’re near empty on your tank it can do weird things. This is the most common cause of inaccurate or erratic DEF level gauge readings. If the DEF fluid level is low, the gauge or dipstick may not accurately reflect the actual DEF level. Faulty DEF level sensor aka DEF sending unit: If the DEF level sensor or wiring is not functioning properly, it may not accurately detect the DEF fluid level and the vehicle's computer system may not display the correct DEF level on the dashboard gauge or dipstick. This can cause the DEF level to fluctuate or appear to be erratic. The DEF level sensor is part of a multi-purpose component that also includes the DEF quality sensor, DEF tank temperature sensor, and DEF tank heater. Please note if you are seeing DEF  fault codes for any of these components you may have a malfunctioning DEF sending unit aka header, which is mounted on top of the DEF tank and looks like a cap with a clamp but has tubes and wiring that goes down into the tank. The following causes pertain more toward that consumption or lack of consumption of DEF, but in some cases can cause incorrect DEF level readings: Leaks in the DEF system: If there is a leak in the DEF tank, pump, lines, or injectors, the DEF fluid level may be low and the gauge or dipstick may not accurately reflect the actual DEF level. Faulty DEF dosing system: If the DEF dosing system is not functioning properly, it may not inject the proper amount of DEF fluid into the exhaust stream. This can cause the DEF to be consumed at an incorrect rate. DEF quality issue: If the DEF fluid is of poor quality or has become contaminated, it may not work properly in the emission control system. This can cause the DEF to be consumed at an inaccurate rate and/or the level to appear low, even if the DEF tank is full. DEF filter: If the DEF filter is plugged up or dirty it can cause inaccurate readings due to higher or incorrect pressures and flow rates. The DEF filter is located on the bottom of the DEF pump and is inside a filter cap. Exhaust system or another issue: If there is a problem with the exhaust system, such as the aftertreatment fuel system, turbocharger or VGT actuator, EGR valve, or a sensor on the engine it may interfere with the proper functioning of the DEF system.   

Decreased fuel efficiency When the EGR valve is stuck open or not functioning properly, it can cause the engine to run less efficiently, resulting in decreased fuel efficiency. Poor engine performance A faulty EGR valve can cause a variety of performance issues, such as a loss of power, rough idle, and hesitation during acceleration. Check engine light The EGR valve is connected to the vehicle's onboard diagnostic system, so if it is not working correctly, it may trigger the check engine light to come on. In some cases, the check engine light may escalate to a 5mph derate if ignored, as the truck may attempt to perform parked regenerations but fail due to the malfunctioning EGR valve. Excessive emissions A failing EGR valve can lead to an increase in emissions, such as carbon monoxide and nitrogen oxides, therefore throwing off the parameters required to complete a parked regeneration. Excessive soot build-up A faulty EGR valve can cause excessive soot buildup in the EGR cooler, EGR differential pressure sensor, venturi pipe, and even the actual valve inside of the EGR valve which can cause it to bind causing it to not open and close properly, which can lead to failed regenerations and other issues.

Decreased Fuel Efficiency If the injector sleeves are not sealing properly, fuel can leak into the combustion chamber, which can lead to increased fuel consumption. This can be frustrating for truck drivers and can also result in higher operating costs. 2. White Smoke If fuel is leaking into the combustion chamber, it may be burned along with the air and diesel fuel, which can result in white smoke being emitted from the exhaust. This can be a visible sign that there is an issue with the injector sleeves. 3. Rough Running Engine If the injector sleeves are not sealing properly, it can cause the engine to run rough or misfire. This can lead to a less smooth ride and can also cause damage to the engine if not addressed. 4. Decreased Power If the engine is not running smoothly, it may not produce as much power as it normally does. This can lead to decreased performance and can also cause problems when pulling heavy loads. 5. Loss of Compression If the injector sleeves are damaged or worn, it can lead to a loss of compression in the cylinders, which can cause the engine to run poorly or not start at all. This can be a serious issue that requires immediate attention. 6. Coolant Loss If the injector sleeves are not sealing properly, coolant may leak into the combustion chamber, which can result in a loss of coolant and potentially cause overheating. This can be a serious issue that can cause damage to the engine if not addressed promptly. 7. Coolant System Contamination Exhaust gases may be introduced to the coolant system if the injector sleeves are not sealing properly. This can cause the coolant reservoir tank to become pressurized and overflow, or the coolant may become discolored and may develop black spots or a dark color. 8. Hard Starting If the injector sleeves are not sealing properly, it can cause difficulty starting the engine. This can be a frustrating issue for truck drivers and can also lead to decreased performance if the engine is not starting properly.