Fault Message:

HYD 2 LO PRESS

Fault Code:

0000H2LP

Associated CAS:

HYD 2 LO PRESS
(Caution)

Data Acquisition Unit (DAU) 2 is reporting both the Engine Driven Pump (EDP) 2A and AC Motor Driven Pump (ACMP) 2B Pressure Switches and System Pressure Transducer are less than 1800 psi with Engines running or Aircraft in a weight off wheels condition.

• Hydraulic Fluid Filter
• Hydraulic System Pressure Relief Valve
• Hydraulic System Pressure Transducer 2 (MT143)
• Engine Driven Pump (EDP) 2A
• AC Motor Driven Pump (ACMP) 2B (B52)
• Data Acquisition Unit (DAU) 2 (A18)
• Secondary Power Distribution Assembly (SPDA) 2 (A14)
• Associated Wiring

Advisory Wire/Service Bulletin:

• 700T-0022 - Hydraulic System-Fluid Transfer
• 700T-0040 - Unapproved Hydraulic Fluid
• 700T-0124 - Hydraulic System Filters: Possible Incorrect Filters Installed in Hydraulic Systems 1, 2 and 3

Forum Articles/Infoservice/Newsletter: None

If there are multiple CAS messages, consider troubleshooting sequencing. When replacing the pressure filters, a hydraulic lock has been known to prevent new filter installation. A "B" nut next to the filter manifold may need to be loosened or removed to bleed off pressure and allow the installation of the filter.

1. Carry out a quantity check of the hydraulic system.

   1. If system low quantity found, service system, check system for leaks and do close out.
   2. If quantity is good continue with next step.

2. Inspect system filter DPI(s).

   1. If DPI tripped, investigate clogged filter and do close out.
   2. If DPI not tripped, continue with next step.

3. Run system 2 AC Motor pump and check system pressure.

   1. If system pressurizes, replace engine pump and do close out.
   2. If fault still present, continue with next step.

4. Run Engine 2 and check system pressure.

   1. If system pressurizes, investigate why AC motor pump is not working and do close out.
   2. If fault is still present, continue with next step.

5. Perform wiring checks between the filter manifold transducer 2 (MT143), DAU 2 and SPDA 2.

   1. If wiring checks are not good, repair defective wiring as required and do close out.
   2. If wiring checks good, continue with next step.

6. Ensure 28 VDC input from SPDA 2 to transducer.

   1. If there is no 28 VDC, continue with next step.
   2. If there is 28 VDC, go to step 8.

7. Swap SPDA 2 with SPDA 4.

   1. If system checks are good, replace SPDA 2 and do close out.
   2. If fault remains, continue with next step.

8. Swap the system manifold transducer 2 (MT143) with system manifold transducer 1 (MT140).

   1. If system checks are good, replace system manifold transducer 2 and do close out.
   2. If fault remains, continue with next step.

9. Swap DAU 2 with DAU 4.

   1. If system checks are good, replace DAU 2 and do close out.
   2. If fault remains, continue with next step.

10. Replace Hydraulic system 2 manifold filter.

    1. If system checks are good, investigate why filter was causing a low pressure condition and do close out.
    2. If fault remains, continue with next step.

11. Swap filter manifold 2 with filter manifold 1.

    1. If system checks are good, replace filter manifold 2 and do close out.
    2. If fault remains, continue with next step.

12. Consider a bypassing hydraulic system component. Such as a reservoir may be bypassing from the high to low pressure side.
13. Do close out.