Case IH 3418 – Engine Control Unit (ECU): ECU Power stages: SCB error on the Turbocharger PWM output power stage

The Engine Control Unit (ECU) has detected a high voltage condition (short to battery) on the circuit responsible for controlling the turbocharger's wastegate via the Pulse Width Modulation (PWM) output power stage.

• Farmall
• skid steer
• Puma
• Maxxum
• Magnum
• Steiger
• TR320
• TV620B
• SR175
• Patriot

1. 1

   Visually inspect the wiring harness running from the Engine ECU to the turbocharger wastegate PWM control valve for chafing, melted insulation, or pinched wires.

2. 2

   Disconnect the harness at the turbocharger PWM valve and at the ECU. Using a multimeter, check the PWM signal wire for continuity to the battery positive (B+) to check for a harness short.

3. 3

   Check the internal resistance of the turbocharger wastegate PWM control valve (electro-pneumatic modulator) to rule out an internal short.

4. 4

   Inspect the ECU connector pins for corrosion, water ingress, or bent pins that might be bridging the PWM output to a power pin.

1. 1

   Disconnect Power

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

2. 2

   Repair Wiring

   If the diagnostic tests revealed a short to battery in the wiring harness, locate the damaged section. Splice and solder in new wiring, sealing it with heat-shrink tubing, or replace the affected harness section.

3. 3

   Replace the PWM Valve

   If the harness tests good but the valve is internally shorted: Locate the turbocharger wastegate vacuum pressure control valve. Disconnect the 2-pin electrical connector, mark and disconnect the pneumatic/vacuum hoses, unbolt the valve bracket and remove the faulty valve. Install the new OEM valve, reconnect the vacuum hoses in their proper orientation, and plug in the electrical connector.

4. 4

   Reassemble and Clear Codes

   Reconnect the battery. Turn the key to the ON position and use a diagnostic service tool to clear the inactive 3418 fault code.

5. 5

   Test Run

   Start the engine and run it under load to ensure the turbocharger boosts correctly and the fault code does not return.