New Holland ENG 3957 – Engine Control Module (ECM / Engine ECU): COM1 Output Short to Ground TWV1or3 Output Short to Ground

The engine controller has detected a short circuit to ground on the "COM1" circuit. COM1 is the common power/ground circuit that drives the Two-Way Valve (TWV) solenoids for fuel injectors 1 and 3 (Bank 1). This indicates that either the engine wiring harness supplying these specific injectors is shorted to the chassis/ground, or the internal solenoid coil of Injector 1 (TWV1) or Injector 3 (TWV3) has failed and shorted to its own metal casing.

• L218
• L220
• SR175
• SV185
• C227
• TR319

1. 1

   Visually inspect the engine wiring harness routing from the Engine ECU to the fuel injectors for chafed insulation, melted wires, or areas rubbing against the engine block.

2. 2

   Disconnect the electrical connectors at Injector 1 and Injector 3 to isolate the injectors from the harness.

3. 3

   Perform a harness continuity test: With injectors and ECU disconnected, use a multimeter to check for continuity between the COM1 harness pins and a known good chassis ground. Continuity indicates a shorted harness.

4. 4

   Perform an injector coil test: Measure resistance across the two pins of Injector 1 and Injector 3. Check for continuity between each injector pin and the metal body of the injector. Continuity to the body indicates an internally shorted injector.

5. 5

   Inspect Engine ECU connectors for water intrusion, corrosion, or bent pins that could bridge circuits to ground.

1. 1

   Disconnect battery

   Disconnect the negative battery cable to prevent electrical arcing or ECU damage during the repair.

2. 2

   Repair or replace wiring harness

   If the harness is faulty: Open the wire loom at the site of the short. Repair the damaged wires using OEM-approved splicing methods and heat-shrink tubing, or replace the entire engine wiring harness if the damage is extensive.

3. 3

   Remove faulty injector

   If an injector is faulty: Remove the high-pressure fuel lines and the hold-down clamp for the shorted injector (Injector 1 or 3). Remove the faulty injector.

4. 4

   Install new injector

   Clean the injector bore thoroughly. Install the new injector using new copper sealing washers and O-rings. Torque the hold-down clamp and high-pressure fuel lines to OEM specifications.

5. 5

   Program ECU

   You cannot simply plug in a new injector. You must use the New Holland Electronic Service Tool (EST) with the ISM DI Engine Tool Software license to write the new injector's QR calibration code into the Engine ECU. Failure to do so will result in poor running conditions and further fault codes.

6. 6

   Verify repair

   Reconnect the battery, bleed the fuel system if necessary, clear the ENG 3957 fault code using the diagnostic tool, and run the engine to verify the fix.