Case IH 3350 – Engine Control Unit (ECU): Terminal 50 (Crank Input) Always On

The engine controller is receiving a continuous, uninterrupted signal that the machine is trying to crank/start for an abnormal amount of time (over 30 seconds). This can lead to starting difficulties, engine stalling, or reduced power output.

• Farmall
• Magnum 235-340 (Series 4)
• Steiger series
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• Patriot Sprayers
• Axial-Flow series

1. 1

   Verify that the ignition switch is not physically sticking in the 'Start' (Terminal 50) position. It should automatically spring back to the 'Ignition/On' position.

2. 2

   Check the wiring between the ignition switch, starter relay, and the ECU for damage, chafing, or a short-to-power that would falsely feed voltage to the crank input pin.

3. 3

   Check if the starter relay contacts have welded shut, causing the crank signal to remain active.

4. 4

   Ensure the battery is not weak and the alternator is functioning properly, as low voltage can cause relays to stick or modules to report erroneous states.

5. 5

   Check if an ECU software update is available, as some OEM troubleshooting steps recommend updating the ECU software for crank input anomalies.

1. 1

   Power Down

   Turn off the ignition, apply the parking brake, and disconnect the battery to prevent accidental cranking or electrical shorts during repair.

2. 2

   Diagnose the Root Cause

   Using a multimeter, trace the Terminal 50 circuit starting from the ignition switch down to the starter relay and ECU to find where the voltage is staying 'high' (active).

3. 3

   Replace the Faulty Component

   If the ignition switch fails to spring back or shorts internally, replace the switch. If the starter relay is stuck closed, replace the relay. If the wiring harness is damaged or shorted, repair or replace the affected harness section.

4. 4

   Reassemble and Reconnect

   Reconnect the battery and ensure all connections are secure.

5. 5

   Reset the System

   Turn the ignition off, then start the machine again to allow the ECU to run its self-check and clear the active code.