Case IH 13011 – Universal Controller (UCM) or Instrumentation Controller (INST): Supply voltage 12VB - voltage too low OR Engine Coolant Temperature Sensor Signal Too Low

Depending on the machine series, this code indicates either the 12-volt power supply on the '12VB' circuit has dropped below the acceptable operating threshold (loss of power to the UCM), or the voltage signal from the engine coolant temperature sensor is out of range low (short to ground or internal failure).

• MAXXUM T4E
• Puma 130
• Puma 145
• Puma 160
• Puma 210
• MX Magnum
• TG Series
• Steiger series
• legacy CVX tractors

1. 1

   Verify the tractor's battery is fully charged and the alternator is outputting correct voltage.

2. 2

   Use the tractor's built-in dot matrix display to access the 'H9 - Voltmeter diagnostic' menu to monitor UCM circuit voltage in real-time while wiggling the wiring harness.

3. 3

   Check the power supply fuses and relays dedicated to the Universal Controller.

4. 4

   Inspect the wiring harness leading to the UCM, specifically the 12VB supply wire (often a yellow wire, circuit 3077) for chafing, corrosion at the pins, or a short to ground.

5. 5

   Disconnect the engine coolant temperature sensor.

6. 6

   Test the resistance of the sensor using a multimeter to see if it matches OEM specifications for the current ambient temperature.

7. 7

   Probe the wiring harness between the sensor and the Instrumentation Controller to check for a short to ground.

1. 1

   Disconnect battery

   Disconnect the battery to prevent electrical spikes.

2. 2

   Repair wiring harness

   Repair or replace any damaged sections of the wiring harness supplying the 12VB circuit to the UCM. Clean any corroded connector pins with electrical contact cleaner.

3. 3

   Replace fuses/relays

   Replace any blown fuses or faulty power relays supplying the UCM.

4. 4

   Reconnect battery

   Reconnect the battery and turn the key switch to the ON position.

5. 5

   Replace Universal Controller

   If the wiring tests perfectly (delivering full battery voltage to the UCM pin under load) but the code persists, the Universal Controller itself has suffered an internal hardware failure and must be replaced.

6. 6

   Clear codes

   Access the tractor's diagnostic menu and use the 'HC' menu to erase all stored fault codes without erasing the tractor's calibration information.

7. 7

   Replace coolant temperature sensor

   If diagnosing the coolant temperature sensor and it fails the resistance test, unthread the old sensor from the engine block and install a new one.

8. 8

   Repair sensor wiring

   If the sensor is good, trace the wiring harness back to the Instrumentation Controller and repair the shorted wire.

9. 9

   Replace Instrumentation Controller

   If both the sensor and wiring are perfectly intact, the Instrumentation Controller has failed internally and must be replaced.

10. 10

    Clear codes

    Clear the fault codes via the instrumentation display.