Case IH PCA – PCU (Powertrain Control Unit / Pump Control Unit): CAN In PCU, Shorted To Low Source

The Controller Area Network (CAN) bus communication line going into the PCU is experiencing a short circuit to a low voltage source (ground). This disrupts the network, preventing the module from sending or receiving critical operational messages.

• MXM
• Case IH MXM 120
• Case IH MXM 130
• Case IH MXM 140
• Case IH MXM 155
• Case IH MXM 175
• Case IH MXM 190

1. 1

   Check for other codes being displayed, as multiple CAN codes can pinpoint a shared harness failure.

2. 2

   Isolate the circuit by turning the power OFF, turning the keyswitch OFF, and disconnecting the battery.

3. 3

   Disconnect the connectors at both ends of the CAN circuit (at the PCU and the Engine Control Module) to prevent false readings.

4. 4

   Measure resistance by setting a multimeter to ohms. Use the black lead to contact a clean, plated metal part on the chassis (ground) and the red lead to touch the connector pins one at a time to determine if the CAN wires are shorted to ground.

5. 5

   Inspect physical components for a faulty connector (corrosion, bent pins) or a damaged/pinched wiring harness.

1. 1

   Locate the Short

   Using the multimeter readings from your diagnostic checks, trace the harness routing to locate the exact point of the short circuit.

2. 2

   Repair or Replace Wiring

   If a damaged wire is found, perform a temporary wiring harness repair. Warning: It is critical that the wire lengths are not altered from the original factory length. Do not attempt to repair wires directly at system sensors.

3. 3

   Address Module Failures

   If the harness and connectors test perfectly fine, the failure mode is likely internal to either the Engine Control Module or the Powertrain Control Unit (PCU). Replace the faulty module.

4. 4

   Reassemble and Clear Codes

   Reconnect all affected connectors. Turn the power back on, clear the error code, and test the system for normal operation.

5. 5

   Recalibrate

   If the PCU (microprocessor) is replaced, or if any mechanical repairs/potentiometer replacements were made, you MUST perform the Transmission/EDC Calibration Set Up Procedure.