The Case IH Selective Catalyst Reduction (SCR) system is crucial for meeting emission standards. However, SCR failures, often indicated by fault codes 19813/E0907 (pressure drop during dosing) and 19298/E0916 (low urea pressure at startup), can disrupt operations. These codes often point to the Dosing Control Unit (DCU) failing to build sufficient pressure. This article explores common causes and troubleshooting steps for Case Ih Scr Failure related to low pressure.
Common Causes of Case IH SCR Failure
Several factors can contribute to low pressure in the SCR system, triggering failure codes:
- DEF Supply Issues: A leaking, restricted, broken, or kinked DEF supply line can prevent the system from achieving the necessary pressure. Additionally, a weak DEF supply pump due to internal leakage or clogged DEF filters can also contribute to this issue. Finally, a low DEF level in the tank can introduce air into the system.
- Air in the System: Air ingress, often caused by low DEF levels, can significantly impact pressure. A leaking suction pickup unit in the tank (WEMA) is a known culprit. Frozen DEF can also restrict flow and introduce air.
- Faulty Sensors: Incorrect readings from the DEF pressure sensor can lead to inaccurate diagnoses and system malfunctions.
- DCU Problems: While less common, a faulty DCU itself can be the root cause of pressure issues, despite replacing the unit multiple times.
Figure 1: A typical SCR system diagram highlighting key components.
Diagnosing Case IH SCR Failure
The Electronic Service Tool (EST) is essential for diagnosing SCR problems. The Urea Dosing System Test (UDST) within the EST provides crucial pressure readings. A healthy system should maintain 4900 to 6200 millibar (71.1 to 89.9 psi) during operation and -50 to -300 millibar (-0.72 to -4.35 psi) during evacuation. Readings outside these ranges indicate a problem. Observing air bubbles in a clear hose installed between the tank and the DCU can confirm air ingress.
Solutions for Case IH SCR Failure
Addressing low pressure issues involves systematically checking and resolving potential causes:
- Inspect DEF Supply Line: Thoroughly examine the DEF supply line for leaks, restrictions, kinks, and damage. Replace any compromised sections.
- Check DEF Pump and Filters: Verify the DEF pump’s functionality and ensure DEF filters are clean and unclogged. Replace as needed.
- Maintain Proper DEF Levels: Keep the DEF tank adequately filled to prevent air intake. Address any leaks contributing to low DEF levels.
- Address Air Ingress: If the WEMA is suspected, inspect for leaks. Newer WEMA units have improved o-ring seals to mitigate this issue. Also, inspect the WEMA for cracks caused by vibration, especially in earlier models without a protective tank recess.
- Verify Sensor Accuracy: If other components check out, investigate the DEF pressure sensor. Compare readings with a known good sensor or consult the service manual for testing procedures.
Figure 2: A technician diagnosing a Case IH SCR system.
Conclusion
Case IH SCR failure due to low pressure can stem from various sources. Systematic troubleshooting, utilizing the EST and focusing on the DEF supply, air ingress, and sensor accuracy, is crucial for accurate diagnosis and effective repair. Regular maintenance and preventative measures can minimize the risk of SCR system failures, ensuring optimal equipment performance and compliance with emission regulations.
