Deutz-Fahr SPN 4334 FMI 6 – ACM 2.1 (Aftertreatment Control Module): AdBlue Dosing Pump: Short circuit to +12V

A critical electrical fault where the supply voltage circuit for the AdBlue (DEF) dosing pump/supply module is shorted to the battery voltage. This prevents the pump from operating, leading to a failure in the SCR (Selective Catalytic Reduction) emissions system and typically causing an engine derate.

• 6105 TTV
• 6110 TTV
• 6120 TTV
• 6130 TTV
• 6140 TTV
• 6150 TTV
• 6160 TTV
• 6170 TTV
• 6180 TTV
• 6190 TTV
• 7200 TTV
• 7250 TTV
• 7300 TTV
• 7340 TTV
• 9300 TTV
• 9340 TTV
• 9370 TTV
• 9400 TTV

1. 1

   Visually inspect the wiring harness between the ACM 2.1 and the AdBlue Dosing Pump for chafing, melted insulation, or pinched wires that could cause a short to battery (+12V).

2. 2

   Disconnect the electrical connector at the AdBlue Dosing Pump (creating an intentional open circuit) and re-read the fault codes. If the code changes to an open circuit code (e.g., SPN 4334 FMI 5), the short circuit is internal to the AdBlue Dosing Pump.

3. 3

   If the fault code remains SPN 4334 FMI 6 after disconnecting the pump, use a multimeter to test the specific supply pins at the ACM connector for continuity to power to verify if the short is in the harness or internal to the ACM 2.1 controller.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the tractor's battery to prevent further electrical damage.

2. 2

   Repair Wiring

   If the diagnostic checks revealed a short in the harness, repair the damaged section of the wiring or replace the SCR sub-harness. Ensure all connections are sealed against moisture.

3. 3

   Replace the AdBlue Dosing Pump

   If the short is internal to the pump: Relieve any residual pressure in the DEF lines. Disconnect the DEF supply and return lines from the pump (be prepared for minor fluid spillage; clean immediately as DEF is corrosive). Unbolt the dosing pump from its mounting bracket. Install the new dosing pump, reconnect the fluid lines, and plug in the electrical connector.

4. 4

   Repair/Replace the ACM 2.1

   If the wiring and pump are both good, the ACM 2.1 has suffered an internal short circuit. The module must be removed and sent to a specialized ECU repair facility or replaced with a new, dealer-programmed unit.

5. 5

   System Prime and Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool to clear the fault codes. Run an SCR system test or dosing quantity test to prime the pump and verify the repair.