Case IH P40 – Engine Control Module (ECM) and Pump Control Unit (PCU): PSG Message, Shorted To High Source

A communication or electrical fault between the Engine Control Module (ECM) and the Pump Control Unit (PCU/PSG) indicating the PSG message circuit is shorted to a high voltage source. The engine remains enabled, but the ECM will restrict (derate) the engine speed to a maximum of 1760 RPM.

• MXM
• MXM120
• MXM130
• MXM140
• MXM155
• MXM175
• MXM190
• TM120
• TM130
• TM140
• TM155
• TM175
• TM190

1. 1

   Visually inspect for a faulty connector, damaged harness, or CAN BUS interference between the ECM and the PCU.

2. 2

   Check for a short to ground: Test between connector C273 pin 5 (PC3–Y) and ground, and between connector C273 pin 7 (2009–G) and ground. Wiggle the harness and connectors to check for an intermittent circuit.

3. 3

   Check for a short to positive (+Ve) voltage: Disconnect connector C315. Turn the key switch to the ON position. Measure the voltage between ground and connector C273 pin 5, connector C273 pin 7, and connector C315 pin 18 (MG128–O). Wiggle the harness to check for an intermittent circuit.

1. 1

   Harness Repair

   If diagnostic checks reveal a short to ground or a short to a high voltage source, locate the chafed or melted wire in the harness. Repair or replace the affected wiring harness section and clear the codes.

2. 2

   Injection Pump Replacement

   If the harness and connectors test perfectly fine (no shorts or open circuits indicated), the failure is internal to the fuel injection pump's Pump Control Unit (PCU). Remove and replace the entire fuel injection pump assembly.