Component Tests and General Diagnostics

DIESEL AFTERTREATMENT VALIDATION- 6.7L





SOOT GENERATION CAUSES AND EFFECTS

When trying to understand the functionality of the exhaust and after treatment system, (more precisely the effects on the Diesel Particulate Filter (DPF)) you must think in terms of standard plumbing principals. Everything flows downstream. Systems and components along the path are affected by the soot in the exhaust, and these components can also contribute to the soot levels (cause and effect).

This overview will attempt to elaborate on the causes and effects of the Soot flowing downstream in the system. The soot originates in the combustion chamber as a by-product of the combustion process. This is the beginning of the stream. All soot generated in the combustion chamber flows downstream. Excessive amounts of soot can be caused by faulty inputs to the engine controller, air handling system leaks or restrictions, fuel contamination, or fuel injectors. Some soot will always be generated. Under proper operating conditions, soot levels will be low and very manageable.

The next component downstream is the EGR. The EGR can be affected by soot coming from the combustion process. The soot can cause the EGR to stick open or closed, or become restricted. If the EGR malfunctions, it can cause soot generation which is then added to system.

The next component downstream is the Turbocharger. The Turbocharger can be affected by soot coming from the combustion process and/or the EGR. If the Turbocharger malfunctions (sticks, or leaks oil or coolant internally), it can cause soot generation which is then added to system.

The next components found downstream are the O2 Sensors. The O2 Sensors can be affected by soot coming from the combustion process, the EGR, and/or the Turbocharger. If an O2 Sensor malfunctions, it can cause (to a much lesser extent) soot generation which is added to system. O2 Sensor codes can be caused by excessive soot.

ALL of the soot generated upstream will land in the DPF. If a vehicle sets a DPF DTC, such as P1451 or P242F, which are related to the calculated amount of soot currently caught in the DPF this means the engine controller has calculated that the DPF is getting full. This number is and estimation, hence the name; "Estimated Soot Load Based on Delta" (ESL/D) and is measured in grams. Sometimes soot levels will be estimated high and set faults and there is little soot in the DPF!

When a DPF fault sets, it is important to root cause the reason the soot landed in the filter and could not be removed through a normal regeneration. Is fuel contamination the issue causing injectors to stick and over fuel? Is the EGR or Turbocharger sticking causing excess soot? Or is it a combination of these?

A DPF should NEVER be replaced without first determining if there is another root cause of the source of the high "Estimated Soot Load Based on Delta" and repairing this issue also. A DPF should also not be replaced without performing the AFTERTREATMENT INSPECTION GUIDELINE procedure. This will visually show you with examples how to determine if replacement of an after treatment component is necessary.
VALIDATION
1. Before starting the validation, confirm on the scan tool that the engine is still at an operating temperature of 180°F (82°C).

NOTE: The following procedure will provide the necessary drive cycle to allow the PCM to learn normal system operation and the ability to detect most after treatment sooting issues. It is not necessary to have a technician perform the 50 minute drive cycle however, the technician must verify Estimated Soot Load Based on Delta" (ESL/D), measured in Grams while driving the vehicle at a steady state speed. The technician will monitor the scan tool while another person drives the vehicle.

2. The technician must perform a short light load steady state drive cycle to ensure the vehicle will operate normally and allow a passive regeneration if necessary during the next step. During the drive cycle monitor Estimated Soot Load Based on Delta" (ESL/D), measured in Grams for a short period to ensure that the Diesel Particulate Filter (DPF) will not plug during the next steps. In addition, illumination of the MIL during the drive cycle indicates that further diagnosis may be required before proceeding.

NOTE: If the soot load threshold for a P242F DTC is reached during this short drive cycle, the mil will illuminate and passive regeneration will not occur.

3. Record the mileage from the vehicle odometer into section 4D "After Treatment Validation Test" of the Diesel Diagnostic Worksheet step 1.
4. Have an associate (porter) drive at the vehicle least 50 minutes at a steady state speed so the RPM is maintained at about 1900. If highway access is not available, use a lower gear on surface streets. A steady throttle is important. Use cruise control if possible.
5. Once the initial 50 minute drive cycle is complete, return to the repair shop and record the mileage from the vehicle odometer into section 4D "After Treatment Validation Test" of the Diesel Diagnostic Worksheet step 2. Turn the ignition key to OFF.
6. Have the associate restart the engine and record the key cycle event into step 3 of section 4D "After Treatment Validation Test" of the Diesel Diagnostic Worksheet.
7. The technician will ride in the passenger seat while monitoring the scan tool. Monitor "Estimated Soot Load Based on Delta" (ESL/D), measured in Grams.
8. Drive the vehicle and maintain steady engine speed of 1800 - 1900 RPM. Use cruise control if possible, (steady throttle pressure).
9. ESL/D should maintain steady or even start to decrease slowly even though truck is NOT in deSoot mode. This is because the latest software may actually "scrub" soot when driving at higher speeds.
10. Ensure vehicle is operating in "Normal" mode. (Not in desoot, desox or denox mode).
11. Take a reading of the ESL/D. Record the ESLD into step 4 of section 4D "After Treatment Validation Test" of the Diesel Diagnostic Worksheet and continue to drive for 10 minutes.
12. Record that the 10 minute drive cycle has been completed in step 5 of section 4D "After Treatment Validation Test" of the Diesel Diagnostic Worksheet.
13. After 10 minutes, take another reading of the ESL/D and record this number in step 6 of section 4D "After Treatment Validation Test" of the Diesel Diagnostic Worksheet.
14. Step 7 of section 4D "After Treatment Validation Test" of the Diesel Diagnostic Worksheet will automatically calculate the estimated soot load difference.
15. Step 8 of section 4D "After Treatment Validation Test" of the Diesel Diagnostic Worksheet will automatically PASS or FAIL based upon results of step 7 of section 4D "After Treatment Validation Test" of the Diesel Diagnostic Worksheet.

Did the ESL/D test pass?

Yes

- Vehicle is properly repaired.

No

- Vehicle is NOT repaired completely. Return back to the test that sent you here or continue diagnosing the vehicle with the ENGINE MISFIRE/RUNS ROUGH/POOR PERFORMANCE test procedure. Checking Engine Misfire / Runs Rough / Performance Test