Case IH 3355 – Engine Controller (ECM / EDC): Main Relay 4 (Engine Brake Exhaust Valve) - Short to Battery or open load

The engine control module has detected an electrical fault—either a broken connection (open load) or a wire that is inappropriately receiving battery voltage (short to battery)—on the circuit that controls the exhaust brake flap actuator via Main Relay 4.

• Case IH Magnum
• Case IH Puma
• Case IH Steiger
• Case IH Vestrum

1. 1

   Visually inspect the exhaust brake flap actuator and Main Relay 4 wiring harness for chafing, melting, or pinched wires

2. 2

   Check connectors at the exhaust brake actuator and the ECM for pushed-out pins, corrosion, or moisture

3. 3

   Perform an open circuit test using a multimeter on the control wire between the ECM, Main Relay 4, and the exhaust brake actuator (infinite resistance indicates a broken wire)

4. 4

   Perform a short to battery test on the control circuit wire with the key ON (engine off) to see if it inappropriately receives 12V

5. 5

   Measure the internal resistance of the exhaust brake actuator solenoid and Main Relay 4 to check for an internal open or short circuit

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Access the Components

   Locate Main Relay 4 in the cab or engine bay fuse panel. Locate the exhaust brake flap actuator near the turbocharger/exhaust stream.

3. 3

   Repair Wiring

   If your diagnostic tests revealed a broken or shorted wire in the harness between the ECM and the actuator, splice and repair the damaged section using weather-sealed connectors, or replace that section of the engine harness.

4. 4

   Replace the Relay

   If the wiring is intact but the relay failed testing, pull Main Relay 4 and replace it with a new OEM equivalent.

5. 5

   Replace the Actuator

   If the actuator solenoid is internally open/shorted, drain the engine coolant (as the exhaust flap actuator is often coolant-cooled on these engines). Unbolt the actuator from the exhaust plumbing, disconnect the electrical connector and coolant lines, and install the new valve. Refill and bleed the coolant system.

6. 6

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic scan tool (like the CNH Electronic Service Tool) to clear the inactive 3355 fault code.

7. 7

   Test Operation

   Start the tractor, bring it up to operating temperature, and verify that the exhaust brake engages properly under load without triggering the code.