What’s That Part?

Have you ever looked under your van and wondered to yourself “What’s that part?” Well on this page you’ll find various components labeled with a brief description on what a part is and what it does. As always your motor configuration may be different from the pictures. So feel free to take a look around your van and compare.

Downstream DEF Pressure Line

The yellow arrow is pointing to the downstream DEF pressure line. This line is after the physical honeycomb filter and is used to determine the fill level of the DEF using the differential pressure sensor.

The red arrow is pointing to the Upstream NOX Sensor. This sensor is used by the CDI and SCR control modules to determine the amount of NOX gases that are being released by the engine. The Upstream NOX Sensor is the used in conjunction with the Downstream NOX Sensor to determine the amount of DEF that should be sprayed into the SCR.

DEF Temperature Sensor

The red arrow is pointing to the DEF temperature sensor. This sensor is used to verify that the DEF is at operating temp. It is also used to keep up with temp for regeneration along with various other temp sensors.

The blue arrow is pointing to the upstream DEF pressure line. This line is used with the downstream DEF pressure line to measure a fill level of the DEF.

The yellow arrow is pointing to the Upstream NOX Sensor but at a better view than the picture to the left.

The white arrow is pointing to the DEF bracket. This bracket may not seem important, but it is actually used to brace the DEF from engine vibration, which can cause the flex pipe (shown by the green arrow) to break. In some cases, this can end up melting the transmission harness and NOX Sensor harnesses.

The green arrow is pointing to the DEF flex pipe, which is the most common failure point we see on the DEF’s.

DEF Injection Valve

The yellow arrow is pointing to the DEF injection valve, or the Metering Valve, in automotive shop terms. This valve sprays the DEF into the SCR to bring down the NOX gases while it goes through the SCR. Most Sprinters meter around 15-30 grams of DEF. The DEF injection valve has two speeds, depending on engine usage and has a spray pattern of 3 streams from super tiny holes.

SCR Temperature Sensor

The yellow arrow is pointing to the SCR temperature sensor. This sensor is used to make sure the SCR is hot enough to burn the DEF and NOX cases off. This component is one of the most replaced components in the AEM campaign, due to the fact that they are almost always being seized in the SCR.

SCR (Selective Catalytic Reduction)

The red arrow is pointing to the SCR (Selective Catalytic Reduction). This component is the second to last piece of the DEF system and has a honeycomb inside. It is used to break down the remaining NOX gases that were not caught by the DPF. The metering valve is mounted to the front of the SCR and sprays directly into the SCR. On a side note, this pipe is a common theft component, unfortunately.

The green arrow is pointing to the Downstream NOX sensor. This sensor reads the NOX gases coming out of the SCR after being broken down by the SCR and sprays the DEF system. It decides how much DEF should be sprayed out of the metering valve to bring the NOX values to the correct levels.

Driver’s Side Charge Air Hose

The yellow arrow is pointing to the driver’s side charge air hose. This is part of the charge air system, or in super basic terms, the turbo system. This hose has two seals on it, and one of the most common issues for a lack of power condition. These hoses should be inspected prior to leaving for a long trip. If this hose is found to be soaked in oil, it should be changed immediately. A common indicator of these hoses either being torn or in bad condition is a large “whoosh” of air under the acceleration.

Passenger Side Charge Air Hose

The yellow arrow is pointing to the passenger side charge air hose. This hose, like the driver’s side hose, should be inspected prior to taking a long trip. It should be replaced along with the driver’s side hose, if found to be torn or oil soaked.

Charge Air Tubing System

The yellow, white, and blue arrows are showing the 3 seals in the charge air tubing. These 3 seals are common areas where boost leaks form, besides the charge air hoses. There shouldn’t be any oil seen on the tubing like there is in the picture. This picture is showing a faulty turbo silencer seal (yellow arrow). These seals should be replaced together when being repaired.

The black arrow is showing the turbo and more specifically where the turbo seal sits. Look for the turbo seal picture on this page.

The orange check is showing the fuel filter. A 5 pin fuel filter to be exact. Check your specific engine for correct fuel filter as they vary by year and are not interchangeable.

The green arrow is showing the glow plug control module. This module is used to send voltage to the glow plugs to heat them up fast. On most Sprinters, the glow plug light is almost unseen due to how fast the plugs heat up. This module rarely goes bad, but a common sign is multiple plugs going out on different sides of the motor.