Case IH P16 – Engine Control Unit (ECU) / Electronic Management Unit: Differential lock solenoid stuck on (P16) / Shut-Off Signal, Shorted To High Source (T16)

P16 indicates the differential lock solenoid is stuck in the 'ON' position. T16 indicates the engine control system has detected a high voltage short in the shut-off signal circuit, typically caused by an incorrect FIP power supply, an internal fault within the FIP, or a CAN BUS communication error on the FIP network, resulting in a 1300 RPM limp mode.

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

1. 1

   For P16: Inspect the Differential Lock Solenoid, as P16 indicates the diff-lock solenoid is stuck in the 'ON' position.

2. 2

   For T16: Turn the keystart OFF and ensure the power is OFF. Disconnect connectors at both ends of the circuit to prevent false readings.

3. 3

   For T16: Inspect the wiring harness running from the ECU to the Fuel Injection Pump (FIP). Look for chafed wire loom, melted insulation, or pinched wires that could be shorting the shut-off signal wire to a 12V power source.

4. 4

   For T16: With the ECU and FIP connectors disconnected, probe the shut-off signal wire for voltage. If voltage is present with the key ON, the wire is shorted to a high source somewhere in the harness.

5. 5

   For T16: Verify the integrity of the CAN High and CAN Low lines between the ECU and the FIP, as this code can also be triggered by a CAN error on the FIP network.

1. 1

   Isolate the Short (T16)

   If your multimeter confirms a short to a high voltage source in the harness, trace the harness routing to find the exact location of the damage.

2. 2

   Harness Repair (T16)

   Cut away the damaged section of the wire. Splice in a new wire of the exact same gauge. Twist the bare leads together, solder or crimp them securely, and seal the repair with heat-shrink tubing or vinyl insulation tape. Re-loom the harness to protect it from future chafing.

3. 3

   FIP Internal Fault (T16)

   If the wiring harness tests perfectly fine (no shorts to power, ground, or open circuits), the fault is likely an internal failure of the Fuel Injection Pump's integrated controller. In this case, the FIP must be removed and sent to a certified diesel injection shop for rebuilding, or replaced entirely.

4. 4

   Reassembly and Testing (T16)

   Reconnect all ECU and FIP connectors. Turn the key ON and clear the fault codes using the tractor's H-Menu or a diagnostic service tool. Start the engine and verify that it can rev past the 1300 RPM limp-mode restriction.