Diagnostic Test
- INSPECTION OF THE DPF NOTE:
The primary failure modes for the DPF are inlet face plugging, internal cracking and internal melting. Inlet face plugging is easily diagnosed. Internal cracking and melting can be identified by soot patterns on the DPF outlet and/or evidence of soot on the outlet tail pipe.
- Remove the DPF from the vehicle.
- Inspect the inlet face of the DPF.NOTE:
DPF Inlet is the flanged side.
- This figure is an example of a failed DPF due to severe face plugging.
All inlet channel openings are completely plugged. Symptoms would possibly include hard or no start and/or related P-codes.
- This figure is an example of a good DPF inlet.
Note that immediately following a regeneration event, the inlet face will/may look cleaner. Also note that it is normal for the inlet face to be coated with soot. Inlet channels should be open and visible. As long as cell matrix is visible the inlet is ok.
- Inspect the outlet of the DPF.
- This figure is an example of a failed DPF due to an internal melting of cells.
The DPF outlet face and pipe show evidence of soot. Symptoms can include Black Smoke, and/or related P-codes.
- This figure is an example of a failed DPF due to an internal cracking of the substrate.
The DPF outlet channel openings show evidence of soot. Close inspection shows several blackened channel openings or 'black cells'. Also the outlet pipe shows evidence of soot. Symptoms can include Black Smoke, and / or related P-codes.
- This figure is an example of a failed DPF due to a leak at the DPF Outlet rim of substrate.
Look for black cells on the outlet face.
- This figure and the next are examples of a good DPF.
In this figure, it is not black or does not show any black cells. Note orange appearance near weep hole at bottom. This is dirt ingestion from dusty areas that does not affect filter performance. Outlet pipe is not sooty as compared to a failed part. Normally outlet face is off white or tan in appearance.
- This figure shows an enlarged section with a small black circle near the center of substrate. This is the only sign of soot evident in the entire outlet inspection. A quick check with a 1" socket will show pass/fail of this part. Using a one inch socket (1.375 inches Outer Diameter) and extension, cover the black spot at the center of DPF outlet face. If the 1 inch socket covers the black spot and no other black cells are visible, DPF doesn't need to be replaced.
If there are any black cells visible around the 1 inch socket, DPF does not meet pass criteria and should be replaced. If there are any black cells on other portions of the outlet face in addition to a black spot in the center, DPF should be replaced.NOTE:
Make sure one inch socket has about 1.375 inches of outer diameter (Standard socket not impact). DPF outlet thermistor may be removed, if it is in the path of the black spot.
Does the DPF show signs of face plugging, internal cracking or melting?
Yes
- Replace the Diesel Particulate Filter (DPF) in accordance with the Service Information.
No
- Go To 2
- INSPECTION OF THE DOC NOTE:
The Diesel Oxidation Catalyst (DOC) is located inside the canister referred to as the Diesel Particulate Filter (DPF)
NOTE:The DOC inlet is the only portion that can be inspected easily. Key modes of failure are FACE plugging, debris and possibly melted channels.
- This figure is an example of a good DOC. Soot is present on the inlet which is normal.
As long as cell matrix is visible the inlet is ok.
Does the DOC show signs of face plugging, internal cracking or melting?
Yes
- Replace the Diesel Oxidation Catalyst (DOC/DPF) in accordance with the Service Information.
No
- Test complete.
- This figure is an example of a good DOC. Soot is present on the inlet which is normal.
As long as cell matrix is visible the inlet is ok.
- INSPECTION OF THE SCR CATALYST NOTE:
The primary failure modes for the SCR are related to Diesel Exhaust Fluid (DEF) deposit formation or damage related to contact with liquid DEF.
DEF buildup inside of the exhaust is a normal occurrence. Small amounts of build up do not harm the system, are not a sign of improper function, and should be consumed during normal operation of the vehicle.
Excessive build up can alter the proper function of the DEF injector and the SCR Catalyst, and should be properly serviced. The service required depends on the type of deposit formation. The following images show differing levels of deposit and the type of action that is required.
- Remove the SCR Catalyst from the vehicle for inspection.
- Inspect the inlet side of the SCR Catalyst. To view the inside of the catalyst, a small borescope will be needed to navigate through the mixing plate.
- The following bullet points show different levels of DEF deposits and the recommended service actions:
- The following images show examples of DEF Injector tip deposits and the recommended service actions:
- The following images show examples of DEF Injector dome deposits and the recommended service actions:
- The following images show examples of DEF pipe wall deposits and the recommended service actions:
- The following images show examples of DEF mixer deposits and the recommended service actions:
- The following images show examples of SCR cone deposits and the recommended service actions. To view this area, a small borescope will be needed to see through the mixer:
- The following images show examples of SCR substrate deposits and the recommended service actions. To view this area a small borescope will be needed to see through the mixer:
Does the SCR show signs of excess deposits?
Yes
- Complete the repair by performing the steps identified under the picture that most accurately represents the deposit condition.
No
- Test complete.