Case IH t89 – Pump Control Unit (PCU): Solenoid Valve Power Stage 2, Data Valid But Above Normal Range

The secondary power supply to the solenoid valve in the Pump Control Unit (PCU) is faulty, causing the tractor to enter limp home mode and restricting engine speed to a maximum of 1760 RPM.

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

1. 1

   Ensure power is OFF, key switch OFF, and disconnect battery if required

2. 2

   Disconnect connectors at the PCU and relay to isolate the circuit and prevent false multimeter readings

3. 3

   Visually inspect the affected connectors and harness outer covering for signs of rubbing, corrosion, or broken pins

4. 4

   Test continuity and resistance using a multimeter to check for shorts to ground and pin integrity

5. 5

   Test the engine shut-down relay (K5) for proper switching and internal resistance

1. 1

   Replace Relay K5

   If the engine shut-down relay (K5) fails testing or is suspect, remove it from the fuse/relay panel and replace it with a new 5-terminal power relay.

2. 2

   Repair Wiring Harness

   Locate the faulty wire using fault code charts and multimeter readings. Cut away the damaged area, strip the ends, twist the two bare leads together, solder the connection, and wrap each repaired lead tightly with vinyl electrical insulation tape. Ensure the tape overlaps the intact cable cover at each end by at least 2 inches (50 mm).

3. 3

   Reassembly

   Reconnect all affected connectors to the Pump Control Unit and the relay block.

4. 4

   Clear Codes & Test

   Reconnect the battery, turn the key switch ON, and verify if the t89 code clears. Start the engine and verify that the tractor can exceed the 1760 RPM limp-mode restriction.