Case IH P8B – Engine Control Unit (ECU) or Pump Control Unit (PCU): Shut-Off Signal, Data Valid But Above Normal Range

Code indicates an issue with the Shut-Off Signal where the data is valid but above the normal range. This is caused by an incorrect fuel injection pump (FIP) supply voltage, an internal fault within the FIP, or a CAN communication error on the FIP CAN BUS network. The engine will enter a 'limp home' condition with reduced performance, restricted fuel quantity, and maximum engine speed hard-limited to 1300 RPM.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• TM115-TM165

1. 1

   Preparation: Turn the keystart OFF and power OFF. Disconnect connectors at each end of the circuit to prevent false readings. Set your multimeter to measure resistance (Ohms) or DC Voltage where specified.

2. 2

   Check for Open Circuit: Check the continuity between connector C273 pin 5 and C316 pin 20, as well as C273 pin 6 and ground. Wiggle the harness and connectors to check for an intermittent circuit.

3. 3

   Check for Short to Ground: Check for continuity between connector C273 pin 5 and ground, and between C273 pin 7 and ground. Wiggle the harness while testing.

4. 4

   Check for Short to Voltage (+Ve): Disconnect connector C315. Turn the keystart ON. Measure the voltage between connector C273 pin 5 and ground, C273 pin 7 and ground, and C315 pin 18 and ground.

1. 1

   Inspect Connectors

   Clean the affected connectors (C273, C315, C316) using a Freon T.F. base contact cleaner. Look for pushed-back pins, corrosion, or moisture.

2. 2

   Repair Harness

   If your diagnostic checks revealed an open circuit, short to ground, or short to voltage, repair or replace the affected section of the engine wiring harness.

3. 3

   Replace Fuel Injection Pump

   If the harness and connectors test perfectly fine, the fault is an internal failure of the Fuel Injection Pump's control module. Remove and replace the Fuel Injection Pump (FIP).

4. 4

   Clear and Retest

   Once the repair is made, use the service tool to clear the error code and test the tractor for normal operation to ensure it exits limp-mode.