Case IH 3977-05 - BCM – Body Control Module (BCM): Cab Dome Light 2 / Sleeper Dome Light Relay Under Current Or Open Circuit

The control module has detected that the electrical circuit for the sleeper or cab dome light is open or drawing less current than expected, which is typically caused by a broken wire, a disconnected connector, a blown light bulb, or a defective relay in the dome light circuit.

• MAGNUM AFS Connect
• International ProStar
• International LoneStar
• International LT series
• Freightliner

1. 1

   Check the sleeper/cab dome light bulb to see if the filament is burnt out.

2. 2

   Inspect the wiring harness and connectors for the dome light circuit (specifically identified as circuit 1601-F2 in Navistar manuals) for any breaks, corrosion, or loose pins.

3. 3

   Test the sleeper dome light relay for proper operation.

4. 4

   Check for 12 volts at the dome light connector to verify power delivery from the BCM.

1. 1

   Disconnect battery

   Disconnect the vehicle's battery to ensure safety before working on the electrical system.

2. 2

   Access dome light assembly

   Access the dome light assembly in the cab or sleeper and remove the lens cover.

3. 3

   Inspect and replace bulb

   Remove and inspect the bulb; replace it if it is blown.

4. 4

   Check wiring continuity

   If the bulb is good, use a digital multimeter to check for continuity in the wiring (circuit 1601-F2) between the BCM and the dome light assembly.

5. 5

   Repair wiring or connectors

   Repair any broken wires or replace damaged connectors in the circuit.

6. 6

   Test and replace relay

   If the wiring is intact, locate and test the dome light relay in the power distribution center; replace the relay if it fails testing.

7. 7

   Reassemble and clear codes

   Reassemble the dome light, reconnect the battery, and clear the fault codes using an electronic service tool.