Written by | Master Truck Repair
Vehicle Configuration
|
Model |
Heavy Truck |
|
Emission |
National Five |
|
ECU |
EDC17CV44 |
|
Engine |
D10.38-50 |
|
After-treatment |
Heavy Truck Third Generation + Self-developed DCU |
|
Fault Phenomenon |
No urea consumption, insufficient power |
Diagnosis Steps
Step 1
Enter ECU to read fault codes, and find a current fault:
P1400 OBD related fault: Used for activating torque limitation in the urea injection control unit (DCU)
Step 2
This fault code indicates a fault in the after-treatment system, and torque limitation has been activated. Need to enter the after-treatment system to read the fault codes.
Step 3
Enter DCU to read fault codes, and find a current fault:
P1D17 Exhaust NOx emission level exceeds 5g/kwh
The reason for the torque limitation is found, it is the super five causing the torque limitation.
Step 4
Analyze the possible reasons for exceeding the emission standards, which are usually a few common points.
-
Urea quality does not meet standards
-
Diesel quality is unqualified
-
NOx sensor issue
-
Urea injection system not working
-
Pipes and nozzles clogged
-
Exhaust temperature sensor
Combining the fault phenomenon of no urea consumption, we decided to first check the urea pump and the pipes, nozzles which are prone to failure.
Step 5
To be safe, I checked the urea quality, dropping a drop of urea on the refractometer’s detection prism, found that the urea solution concentration was 32.5%, and the urea quality was qualified.
Step 6
Remove the nozzle, use diagnostic tools to drive the urea pump, found that the urea pressure could quickly rise to 3bar, but no urea came out of the nozzle, only air, suspecting if the injection valve has a problem.
Step 7
Remove the urea pump, measure the resistance of the injection valve at 2.3MΩ, the normal resistance should be around 48Ω, clearly damaged, replace the injection valve, and the urea pump works normally.
Tips
When encountering emission exceeding problems, repair should be based on the fault phenomenon: Is urea being consumed? If urea is being consumed, check urea quality, NOx sensor or original emissions. If no urea is being consumed, the focus should be on checking the exhaust temperature sensor, urea pump, and whether the pipes are clogged.
END
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