Case IH 19879 (F-3360-14) - ECU – Engine Control Unit (ECU) / Vehicle Control Module (VCM): Heater control unit reports missing voltage at Terminal 30

The Heater Control Unit (HCU), which is responsible for managing the DEF/AdBlue heating system, is not receiving constant battery power (Terminal 30). The system is flagging an open circuit, blown fuse, or faulty relay on this specific power feed.

• VESTRUM CVX
• Case N-Series TLBs (580N, 580SN, 590SN)
• Komatsu WB93R-8
• Komatsu WB93S-8
• Komatsu WB97R-8
• Komatsu WB97S-8

1. 1

   Verify overall battery health and ensure the system voltage is within normal operating range

2. 2

   Inspect the specific fuse supplying Terminal 30 power to the DEF/AdBlue Heater Control Unit

3. 3

   Test the AdBlue line heater relay (often designated as Relay 158) to ensure it is switching properly and not stuck open

4. 4

   Disconnect the harness at the HCU and use a multimeter to check for battery voltage at the Terminal 30 pin. If voltage is absent, check for an open circuit, chafed wire, or corroded connector between the fuse/relay panel and the HCU

1. 1

   Power Down

   Turn off the machine and disconnect the negative battery terminal to ensure safety while working on the electrical system.

2. 2

   Inspect the Relay

   Access the main electrical panel. Pull the AdBlue line heater relay. Test it with a multimeter for continuity across the coil and switch pins. If it fails, replace the relay.

3. 3

   Check the Fuse

   Inspect the Terminal 30 HCU fuse. If it is blown, do not simply replace it—first, inspect the DEF supply and backflow line heaters for a short to ground, which is a common cause for this fuse to blow.

4. 4

   Trace the Circuit

   If the fuse and relay are good, trace the Terminal 30 wire from the electrical panel down to the Heater Control Unit. Repair any broken wires or clean any corroded pins in the connectors.

5. 5

   Reassemble and Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool (such as the Case Electronic Service Tool or EASY Station) to clear the 19879 (F-3360-14) fault code.

6. 6

   Verify Repair

   Run the machine and monitor the DEF/AdBlue system parameters to ensure the HCU is communicating and receiving power.