Case IH 3670 – Engine ECU: Short circuit to battery on Out2 error for H-bridge

The engine control module uses an internal "H-bridge" circuit to reverse electrical polarity to the Exhaust Gas Recirculation (EGR) valve motor, allowing it to drive the valve open and closed. This code indicates that the controller has detected a short circuit to battery voltage on the Output 2 circuit (specifically Pin A35 on the 60-pin engine connector) that drives the EGR valve.

• Farmall
• Maxxum
• Puma
• Magnum
• Steiger
• SR175
• SV series

1. 1

   Disconnect the engine wiring harness from the EGR valve and the 60-pin Engine ECU connector and inspect both for pushed pins, corrosion, or water intrusion.

2. 2

   Using a multimeter, test the wire corresponding to ECU Pin A35 (EGR Out2) for a short to battery voltage.

3. 3

   Check the EGR valve motor pins for an internal short circuit, as an internal failure in the EGR valve's electronic actuator is a common cause.

4. 4

   Verify the vehicle's electrical system voltage to ensure high voltage fluctuations or alternator overcharging are not triggering the fault.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery cable.

2. 2

   Isolate the Short

   If the multimeter test reveals a short to battery in the wiring harness between the ECU and the EGR valve, trace the harness to find the chafed wire rubbing against a power source. Repair or replace the damaged harness section.

3. 3

   Replace the EGR Valve

   If the wiring harness tests good but the EGR valve actuator is internally shorted, remove the mounting bolts and the exhaust/intake plumbing connected to the EGR valve. Install the new EGR valve with new gaskets.

4. 4

   ECU Replacement

   If the wiring is intact and the EGR valve is functioning properly, the H-bridge driver inside the Engine ECU may be permanently burned out. The ECU will need to be replaced or sent out for repair.

5. 5

   Relearn Procedure

   Reconnect all harnesses and the battery. Use a Case IH Electronic Service Tool (EST) to clear the fault codes. If the EGR valve or the Engine ECU was replaced, you must use the service tool to perform the "EGR Valve Self-Learning/Calibration" procedure so the ECU can learn the new valve's end-stops.