New Holland ENG 3808 – Engine ECU (EDC): Fuel Metering Unit: Set point of metering unit in idle mode not plausible.

The Engine Control Unit (ECU) is commanding a specific fuel pressure or flow rate to the fuel metering unit during low idle, but the actual system response does not match the expected set point. This mismatch indicates an inability to maintain or accurately control fuel pressure at idle.

• L220
• L225
• L230
• C232
• SR175
• T4.55
• T4.65
• T4.75
• T4.90
• T4.100
• T4.110
• T5.75
• T5.85
• T5.95
• T5.105
• T5.115
• TD4
• TD5
• W50C
• W60C
• W70C
• W80C
• B95C

1. 1

   Connect an Electronic Service Tool to confirm the fault code is active

2. 2

   Check for low fuel pressure before or after the gear pump (lift pump). Inspect for clogged fuel filters, restricted lines, or external fuel leakage

3. 3

   Inspect the high-pressure fuel lines and rail for any signs of leakage

4. 4

   Check the fuel rail pressure relief valve to ensure it is not stuck open or leaking fuel back into the return system

5. 5

   Perform an injector leak-off test to check for worn or stuck-open fuel injectors

6. 6

   Check the high-pressure fuel pump (Bosch CP4) for low efficiency or internal wear, and test the fuel metering unit's electrical circuit and operation

1. 1

   Prepare the Machine

   Park on a level surface, turn off the engine, and allow the system to cool. Warning: Relieve all fuel system pressure before opening any lines, as high-pressure diesel can cause severe injury.

2. 2

   Address Low-Pressure Restrictions

   If diagnostic checks revealed low pressure from the tank, replace the primary and secondary fuel filters. Repair any leaks in the low-pressure feed lines.

3. 3

   Replace Leaking Components

   If the fuel rail pressure relief valve is leaking, replace the valve. If an injector failed the leak-off test (excessive return flow), replace the faulty injector(s) and program the new injector codes into the EDC using the service tool.

4. 4

   Replace the Fuel Metering Unit / Pump

   If the injectors and PRV are intact, the fault lies with the fuel metering unit or the high-pressure pump itself. If the Bosch CP4 high-pressure pump has failed internally and metal debris is found, the entire high-pressure pump must be replaced, and the fuel lines, rail, and injectors must be flushed or replaced. If no debris is present and the metering unit is electrically/mechanically faulty, replace the fuel metering unit (FCA) on the pump.

5. 5

   Clear Codes and Test

   Use the Electronic Service Tool to clear code 3808. Start the engine, let it idle, and verify that the code does not return and that rail pressure matches the ECU's commanded set point.