The following snapshots are intended to show you how to “interpret” the information recorded. Use the examples to try to determine what area contains the fault.
Due to the variety of operating conditions that affect actual EGR flow and Turbo boost or speed readings, the following examples SHOULD NOT be used as a good vs. bad criteria.
Each snapshot that follows was controlled during running on a chassis dynamometer.
Some failures were induced to display the logic used to determine what is wrong with a particular area of the engine.
- Idle operation with EGR. See Figure "Engine at Idle with EGR Flowing" .
- Cold Idle operation without EGR flow. See Figure "Idle — Cold Engine — No EGR Demand — No EGR Flow" .
- Throttling without load, EGR is on and off. See Figure "Throttling Without Load — EGR is On and Of" .
- 1500 rpm throttling no EGR. See Figure "1500 — No Load — EGR Off" .
- EGR Valve stuck open. See Figure "Start Up — EGR Valve Stuck Open" .
- 147 14, EGR Flow too Low. See Figure "Code 147 14 — EGR Flow Too Low" .
- 146 2 EGR leak – boost. See Figure "146 2 EGR Leak — Boost Power" .
- Leaking Charge Air Cooler. See Figure "Leaking Charge Air Cooler" .
- Delta P port plugged (graph). See Figure "One of the Delta P Ports Plugged in the Delivery Pipe" .
- Normal Acceleration – Automatic Transmission. See Figure "Normal Operation — Eaton Autoshift Transmission" .
- Typical EGR flow loaded. See Figure "Normal EGR Flow with Request" .
- Normal Operation EGR off, Colder ambient. See Figure "Normal — EGR Off" .
- Plugged Delta P port (EGR tab). See Figure "Plugged Delta P Port" .
Normal Engine Operation as Viewed With DDDL Snapshots
It is important to understand what Normal looks like During normal engine operation, all parameters should have smooth transitions.
Review the snapshots in this section for examples of normal engine operation.
EGR Flow at Idle
Detroit Diesel EGR Engines will flow EGR @ idle, as certain conditions are met. MY-2002 EGR engines will flow EGR for a short duration if DDEC determines a quick rise (snap-acceleration) in engine rpm’s over time. Engine parameters programmed determine the duration of EGR flow. There is a time duration difference between MY-2002/03 - 2004.
Delta P Sensor and Piping
The Delta P sensor monitors the pressure differential across the venturi by readings from the two openings in the delivery pipe.
High Delta P with NO Flow Demand (PWM2 % = 7)
If the EGR valve is closed (7%) and the EGR temperature is between inlet manifold and engine temperature there should be little to no actual EGR flow. If the Delta P sensor is registering a high differential pressure in this condition:
- Check for the pressure signal pipe of hose to one side of the sensor is plugged or leaking (includes sensor mounting o rings).
- The sensor being defective is the least likely.
- Incorrectly wired (replacement sensor).
Low Delta P with Flow Demand (PWM2 % greater than 7 and less than 90)
If the EGR valve is open and the EGR temperature is elevated there should EGR flow.
If the Delta P sensor is registering a low differential pressure in this condition: it is likely that the pressure signal to both sides of the sensor are plugged or leaking Lastly, a defective sensor.
Stuck or Sticking VNT or EGR Valve Actuator
When the actuator is sticking, DDEC can’t control turbocharger speed or EGR flow smoothly. Turbocharger speed and PWM 4- VNT % will fluctuate greatly. If the EGR actuator is sticking you are able to see EGR flow with the PWM2 % staying at 7% (which is closed). The engine's temperature can be a factor in this operation.
DDEC is attempting to control turbocharger speed and is overcompensating with PWM4 in an attempt to control turbocharger speed.
Turbocharger Speed Sensor Faults
Turbocharger speeds rarely exceed 100,000 rpm for any length of time. Speeds exceeding 100krpm and dropping rapidly is a warning sign. 30krpm changes in speed at 1 second intervals is almost impossible. Consider a false signal being sent to the ECM rather than this event actually occurring. The ECM is responding to the signals it is receiving from sensors.
Monitor the turbocharger speed and the engine boost, watch for normal, expected changes. Note in one of the next snap shot samples that the turbocharger speed reaches 108,000 rpm and boost is only 7.1psi. Turbo Speed Sensors (pn 23530252) that have a date code stamped on the sensor connector between 0703 to 3703 should be changed first if suspect then contact DDC Customer Support Center at 313-592-5800 for further assistance.
Note: Remember that if a sensor fails and sends a signal to the ECM that is within a normal threshold for that sensor. No code will be generated however DDEC could try to respond to the false signal.
The Variable Pressure Orfice (or Output) Device is used to control the pressure to the actuators used for the EGR valve and turbocharger vane position. The most common failure is external leakage of air. You can hear the leak when you activate the PWM for each VPOD.
Relative Humidity/Turbo Compressor Inlet Temperature Sensor
This sensor is a DDC part installed and wired by the OEM. Most faults here have been due to incorrectly wired 10 pin connector. The ECM will usually log a fault code for one or the other side this combination sensor.
Turbo Compressor Outlet Temperature
During heavy loaded operation the outlet of the turbo to the charge air cooler becomes very hot. Logic built into DDEC allows for derating of torque to reduce these temperatures to prevent charge air cooler failures. The derate code (flash code 49) of 404 14 logs without turning on the check engine light. This inactive code is stored to allow technicians the ability to assure the driver there is not any fault of failure and this operation is normal to the EGR system.
EGR Flow Troubleshooting Tips
Figure 1. Engine at Idle with EGR Flowing
Figure 2. Idle — Cold Engine — No EGR Demand — No EGR Flow
Figure 3. Throttling Without Load — EGR is On and Of
Figure 4. 1500 — No Load — EGR Off
Figure 5. Start Up — EGR Valve Stuck Open
Figure 6. Code 147 14 — EGR Flow Too Low
Figure 7. 146 2 EGR Leak — Boost Power
Figure 8. Leaking Charge Air Cooler
Figure 9. One of the Delta P Ports Plugged in the Delivery Pipe
Figure 10. Normal Operation — Eaton Autoshift Transmission
Figure 11. Normal EGR Flow with Request
Figure 12. Normal — EGR Off
Figure 13. Plugged Delta P Port
|Series 60 EGR Technician's Manual - 7SE60|
|Generated on 10-13-2008|