Case IH P18 – Engine Control Module (ECM): PCU Power Supply, Shorted To High Source

This code indicates a failure in the Pump Control Unit (PCU) power supply circuit. The system has detected that the voltage supplying the PCU is shorted to a high voltage source (above the normal operating range).

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• TM120
• TM130
• TM140
• TM155
• TM175
• TM190

1. 1

   Verify if an external power supply (like a jump starter) is currently connected and causing an over-voltage condition

2. 2

   Check the tractor's charging system (alternator) for a faulty voltage regulator causing over-voltage

3. 3

   Inspect the Engine Shut-Down Relay (Relay K5) for internal shorts

4. 4

   Inspect the wiring harness for a short circuit or short to ground

5. 5

   Verify the internal circuitry of the fuel injection pump

1. 1

   Preparation

   Turn the power OFF and the keyswitch OFF. Disconnect connectors at each end of the circuit to prevent false readings.

2. 2

   Harness Short Circuit Test

   Disconnect connector C273. Using a multimeter, check for continuity/resistance between the following points: C273 pin 1 (5420–G) and C273 pin 2 (5400–Y); C273 pin 1 (5420–G) and ground; C273 pin 2 (5400–Y) and ground; C273 pin 5 (PC3–Y) and ground.

3. 3

   Wiggle Test

   Wiggle the harness and the connectors to check for an intermittent circuit. If a short circuit or short to ground is indicated, repair or replace the harness as required.

4. 4

   CAN BUS Wire Inspection

   Check the CAN BUS wires (Yellow and Green). If the CAN BUS wires are not twisted together or are suffering from electromagnetic interference, repair, re-position, or replace the harness.

5. 5

   Terminating Resistor Test

   Re-connect connector C316. Measure the resistance between connector C273 pin 1 (5420–G) and C273 pin 2 (5400–Y).

6. 6

   Module Replacement Logic

   If the resistance indicated is NOT approximately 120 Ohms, the terminating resistor is faulty. Remove and replace the Engine Control Module (ECM). If the resistance indicated IS approximately 120 Ohms, the CAN BUS terminating resistor in the ECM is okay. The fault lies within the pump itself. Remove and replace the Fuel Injection Pump.

7. 7

   Clear Codes

   Once the repair is complete, use the Electronic Service Tool to clear the logged T18 / 3605-3 code.