John Deere 4376.14 – ECU: DEF Dosing System Powerdown Fault

The DEF dosing system could not be powered down properly. When a John Deere engine is shut off, the aftertreatment system initiates a purge cycle. The DEF dosing unit's reversing valve switches over, and the pump runs backward to drain the Diesel Exhaust Fluid (DEF) out of the lines and back into the tank. If the system still detects pressure in the DEF lines after the purge cycle is supposed to be complete, this code is triggered.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 5M series
• 5R series
• 6M series
• 6R series
• 7R series
• 8R/8RT/8RX series
• 9R/9RT/9RX series
• S-Series combines (S660-S790)
• R-Series sprayers
• G-Series excavators
• K-Series wheel loaders
• L-Series wheel loaders
• backhoes
• knuckleboom loaders

1. 1

   Verify Operator Powerdown Habits: Ensure the battery disconnect switch is not being turned off immediately after shutting down the engine. The DEF system requires up to 5–10 minutes of battery power after key-off to complete the purge cycle.

2. 2

   Inspect Wiring and Connections: Check the electrical harness and connectors at the DEF Dosing Unit (specifically the reversing valve circuit) for corrosion, frayed wires, or loose pins.

3. 3

   Check for Line Blockages: Inspect the DEF suction and pressure lines for kinks, blockages, or frozen fluid that could physically prevent the system from draining back into the tank.

4. 4

   Test System Components: Use John Deere Service ADVISOR (or equivalent diagnostic software) to run a DEF system leak test and manually command the reversing valve and pump to verify operation.

5. 5

   Check for Software Updates: Verify if the ECU has the latest software calibration, as some powerdown logic issues are resolved via ECU flashes.

1. 1

   Depressurize and Clean

   Ensure the machine has been off for at least 15 minutes. Clean the area around the DEF Dosing Unit thoroughly to prevent dirt from entering the DEF system.

2. 2

   Disconnect

   Unplug the main electrical connector to the DEF pump. Disconnect the DEF supply, pressure, and backflow lines. (Have a catch pan ready for residual fluid).

3. 3

   Remove the Pump

   Unbolt the DEF Dosing Unit from its mounting bracket.

4. 4

   Install the New Unit

   Mount the replacement DEF Dosing Unit. Reconnect the DEF lines (ensure they click securely into place) and plug in the electrical connector.

5. 5

   Replace the Filter (Optional but Recommended)

   If not included with the new pump, install a new DEF pump filter kit.

6. 6

   Prime and Reset

   Turn the key to the ON position to allow the system to prime. Connect your diagnostic software, clear the inactive 004376.14 fault code, and run a DEF dosing system prime/override test to ensure there are no leaks and the system builds pressure correctly.

7. 7

   Verify Powerdown

   Run the engine for a few minutes, shut it down, and wait to ensure the purge cycle completes successfully without throwing the code again.