Case IH P77 – Pump Control Unit (PCU): Control Duration, Shorted To High Source

The fuel delivery solenoid activation time control duration is incorrect. The control signal is shorting to a high voltage source, which disrupts the fuel timing and delivery, typically resulting in an immediate engine shut-down.

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

1. 1

   Check for an Open Circuit: Test continuity between connector C273 pin 5 and C316 pin 20, C273 pin 8 and C316 pin 35, and C273 pin 6 and ground. Wiggle the harness and connectors during testing to check for an intermittent circuit.

2. 2

   Check for a Short to Ground: Test between connector C273 pin 5 and ground, and C273 pin 8 and ground.

3. 3

   Check for a Short to Positive Voltage (+Ve): Turn the keystart to the ON position. Measure the voltage between connector C273 pin 5 and ground, and C273 pin 8 and ground.

1. 1

   Harness Repair

   If the diagnostic checks reveal an open circuit, a short to ground, or a short to positive voltage, locate the damaged section of the wiring harness. Repair or replace the harness as required.

2. 2

   Component Replacement

   If the wiring harness and connectors test perfectly fine, the failure is internal to the Pump Control Unit (PCU) / fuel delivery solenoid. You must remove and replace the entire fuel injection pump assembly.

3. 3

   Clear Codes

   Once the repair is complete or the pump is replaced, use the electronic service tool to clear the error code from the system.