Case IH 19440 – Engine Control Module (ECM): Open load error on the PWM output power stage for the Engine Speed

The Engine Control Module (ECM) is attempting to broadcast the engine speed (RPM) via a Pulse Width Modulated (PWM) electrical signal to another module on the machine, but it detects an 'open load'. This indicates that there is no electrical resistance on the circuit, meaning the connection is physically broken, unplugged, or the receiving module is not registering the signal.

• Tier 4b
• Magnum
• Maxxum
• Steiger
• N-Series Loader Backhoes
• 580N

1. 1

   Visually inspect the wiring harness running from the Engine ECM to the cab bulkhead and instrument cluster for chafed wires, rodent damage, or disconnected plugs.

2. 2

   Disconnect the ECM harness and the receiving module (instrument cluster/display) harness to inspect the pins for corrosion, moisture, or backed-out terminals.

3. 3

   Perform a continuity test using a digital multimeter to measure the resistance from the engine speed PWM output pin on the ECM to the corresponding input pin on the receiving module. An infinite reading (OL) confirms a broken wire.

4. 4

   Perform a short-to-ground test on the engine speed wire to ensure it hasn't rubbed bare against the frame.

1. 1

   Power Down

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

2. 2

   Isolate the Break

   If the continuity test reveals an open circuit, trace the harness along the chassis to locate the break. Pay special attention to pinch points, articulation joints, and bulkhead connectors where the harness enters the cab.

3. 3

   Repair the Wiring

   If a broken wire is found, strip back the insulation, use an OEM-approved weather-sealed butt connector (or solder and heat shrink), and repair the connection. If a connector pin is corroded or lacks tension, use a pin-extraction tool to remove the bad terminal and crimp on a new pigtail/pin.

4. 4

   Module Verification

   If the wiring harness tests perfectly (good continuity, no shorts), the fault lies in either a failed receiving module (instrument cluster) or a burned-out PWM power stage inside the Engine ECM itself.

5. 5

   Reassembly and Clearing

   Reconnect all harnesses and the battery. Turn the key on and use the CNH Electronic Service Tool (EST) to clear the inactive fault codes. Start the engine and verify that the tachometer works and the code does not return.