New Holland ENG 3355 – Engine Control Module (ECM / EDC7): Main Relay 4 (Engine Brake Exhaust Valve) - Short to Battery or open load

The engine control module has detected that the electrical circuit controlling the exhaust brake valve actuator (via Main Relay 4) is either broken (open circuit) or is receiving unintended voltage (short to battery).

• T6.125
• T6.140
• T6.150
• T6.155
• T6.160
• T6.165
• T6.175
• T7.220
• T7.235
• T7.250
• T7.260
• T7.270
• T8.320
• T8.350
• T8.380
• T8.410
• CR9090
• CX8080 Elevation
• CX8090 Elevation

1. 1

   Locate Main Relay 4 (Exhaust Valve Relay) in the main fuse/relay panel. Swap it with a known good relay of the same type to see if the code clears, and test the relay for internal shorts or an open coil.

2. 2

   Disconnect the harness at the exhaust brake valve actuator and at the Engine ECU. Check the signal wire for continuity (to rule out an open load) and check for voltage on the wire when the circuit should be dead (to rule out a short to battery).

3. 3

   Measure the resistance across the pins of the exhaust brake valve actuator. If the reading is completely open (infinite resistance) or shorted, the actuator itself has failed.

4. 4

   Inspect the connectors at the exhaust brake valve and the ECU for corrosion, pushed-out pins, or water ingress, which commonly causes short to battery phantom voltage readings.

1. 1

   Power Down

   Turn off the tractor, remove the key, and disconnect the negative battery terminal to prevent electrical spikes.

2. 2

   Replace Relay

   If Main Relay 4 failed the diagnostic check, replace it with a new OEM relay and clean the fuse block terminals.

3. 3

   Repair Wiring

   If a short or break was found in the harness between the ECM and the exhaust brake valve, splice and heat-shrink the damaged section of the wire, or replace the affected harness section.

4. 4

   Replace the Exhaust Brake Valve

   Locate the exhaust brake valve assembly on the exhaust system (usually downstream of the turbocharger). Disconnect the electrical connector and the pneumatic/hydraulic lines (if applicable). Unbolt the actuator/valve assembly from the exhaust pipe. Install the new exhaust brake valve, ensuring the mechanical flap moves freely. Reconnect the electrical connector.

5. 5

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool to clear the ENG 3355 code. Start the engine and test the exhaust brake functionality to ensure the code does not return.