Case IH 19444 – Engine Control Unit (ECU): Short circuit to ground error on the PWM output power stage for the speed output.

The Engine Control Unit (ECU) has detected that the Pulse Width Modulated (PWM) signal circuit—which the engine computer uses to broadcast the engine speed (RPM) to other modules (such as the instrument cluster/tachometer or transmission controller)—has shorted to the chassis ground.

• Tier 4b
• CASE N Series Loaders
• 580N
• 580SN
• 590SN
• Case IH tractors
• Case IH harvesters

1. 1

   Inspect the engine wiring harness routing from the Engine ECU to the vehicle cab/instrument cluster for chafing or rubbing against the engine block, frame, or moving parts.

2. 2

   Disconnect the ECU connectors and check for moisture, corrosion, or bent pins that could be bridging the PWM speed output pin to a ground pin.

3. 3

   With the battery disconnected and the ECU unplugged, use a multimeter to measure the resistance between the PWM speed output wire on the harness side and a known good chassis ground.

4. 4

   If the wiring harness tests perfectly fine (open circuit to ground), check if the short circuit is internal to the ECU's power stage.

1. 1

   Turn off the machine's ignition and disconnect the negative battery cable.

2. 2

   Locate the Engine Control Unit (ECU) mounted on the side of the FPT engine.

3. 3

   Disconnect the main engine wiring harness from the ECU.

4. 4

   Using the machine's specific wiring diagram, identify the pin for the "PWM Engine Speed Output."

5. 5

   Probe this wire with a multimeter set to Ohms (Ω) against the chassis ground.

6. 6

   If a short to ground is confirmed, physically trace the wire through the loom.

   Pay special attention to tight bends, areas near the exhaust/EGR components, and bulkhead pass-throughs.

7. 7

   Once the damaged section of the wire is found, cut out the damaged portion, splice in a new section of wire using weather-sealed heat-shrink butt connectors, and re-loom the harness.

8. 8

   If the wire tests good and no short is found in the harness, the ECU's internal power stage has failed. The ECU must be replaced and programmed.

9. 9

   Reconnect the ECU and battery.

10. 10

    Connect the CNH EASy diagnostic tool (or equivalent CAN-bus reader) to clear the inactive fault codes.

11. 11

    Start the engine and verify that the tachometer reads correctly and the fault code does not return.