Case IH 2669 – Transmission Control Unit (TCU): ZTC - Internal power supply plausibility fault (VPS1)

The fault indicates a plausibility error regarding VPS1 (Valve Power Supply 1), meaning the controller is detecting a state that contradicts its commands (e.g., switched on but measured off, or switched off but measured on). This points to an electrical inconsistency, such as a short circuit, open circuit, or defective connection.

• Steiger T4B
• Puma
• Maxxum
• CVX

1. 1

   Check the cables running from the gearbox to the TCU for visible damage or breaks

2. 2

   Check the connectors at both the gearbox and the TCU for corrosion, moisture, or defective pins

3. 3

   Test for shorts to battery voltage to verify if the VPS1 cable or connectors are making unintended contact with battery voltage

4. 4

   Test for shorts to ground or open circuits to ensure the circuit has continuity and is not grounding out against the tractor chassis

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical damage.

2. 2

   Inspect Connectors

   Disconnect the main wiring harness at the Transmission Control Unit (TCU) and at the transmission valve block. Inspect for pushed-back pins or water ingress.

3. 3

   Continuity Test

   Using a multimeter, measure the continuity of the VPS1 wire from the TCU connector to the transmission solenoid connector. Replace or repair the wire if resistance is high or the circuit is open.

4. 4

   Voltage Test

   Reconnect the battery (with the TCU disconnected) and test the VPS1 wire for voltage to ensure it is not shorted to a power source.

5. 5

   Component Isolation

   If the wiring harness tests perfectly, the fault lies internally within either the transmission solenoid valve block (shorted solenoid) or the TCU itself (internal power supply failure).