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Home / DTC / U02BF — Lost Communication With Interior Lighting Control Module B

U02BF — Lost Communication With Interior Lighting Control Module B

Detailed page for trouble code U02BF.

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22,461specific
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Code

U02BF

Generic U — Network/User

Lost Communication With Interior Lighting Control Module B

Brand: Generic
Type: U — Network/User
Views: UK: 11 EN: 30 RU: 16
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Page language: EN

Causes

  • Faulty Interior Lighting Control Module B (software fault or hardware failure)
  • Loss of module power (blown fuse, open supply, poor connector)
  • Loss of module ground
  • Open, shorted or damaged CAN/LIN bus wiring or connector
  • Missing or failed network termination (resistor open or short)
  • Faulty gateway, BCM or other network node preventing forwarding

Symptoms

  • Interior lighting (dome, map, ambient lights) inoperative or intermittent
  • Warning or message on dash indicating lighting fault or communication error
  • Other modules unable to control or report status of interior lights
  • Multiple related U0xxx communication codes present
  • Possible battery drain if module is stuck on or wiring shorted

What to check

  • Use a scan tool to confirm U02BF and check for additional U-codes or freeze frame data
  • Attempt direct communication with Interior Lighting Control Module B via scan tool
  • Verify battery voltage (12V exact range) and key-on voltage stability
  • Inspect relevant fuses and module power/ground pins for continuity
  • Visually inspect module connectors and harness for corrosion, damage, or pin push-out
  • Measure CAN bus idle voltages: CAN_H ≈ 2.5V, CAN_L ≈ 2.5V (or CAN_H ~2.5–3.5V, CAN_L ~1.5–2.5V depending on vehicle)

Signal parameters

  • CAN bus idle voltages: CAN_H ≈ 2.5 V and CAN_L ≈ 2.5 V (differential 0 V idle), typical dominant state CAN_H ≈ 3.5–4.0 V, CAN_L ≈ 0.5–1.5 V
  • Expected message interval: typically 50–1000 ms depending on manufacturer (module should transmit periodic status)
  • Network timeout threshold: communication considered lost after several missed message intervals (commonly 1–5 seconds)
  • Typical CAN bus termination resistance: ≈ 60 ohms measured across CAN_H and CAN_L
  • LIN bus idle: pulled to battery via resistor (approx. VB), single-wire frames expected on LIN if present

Diagnostic algorithm

  1. Retrieve all stored U-codes and freeze frame data with a dealer-level or full-function scan tool. Note if multiple nodes report loss of the same module.
  2. Attempt to communicate with Interior Lighting Control Module B. If no response, record scan tool error responses.
  3. Check fuses and relay(s) for the lighting module circuit. Verify ignition/wakeup power present at the module power pin with relevant terminals connected as required.
  4. Verify module ground(s) for low resistance to chassis (use backprobe or connector pin measurement). Repair bad ground if found.
  5. Visually inspect the module connector and wiring for damage, corrosion, bent pins, or water intrusion. Repair as needed.
  6. With ignition on, measure CAN_H and CAN_L at the module connector: verify idle voltages and then use an oscilloscope/CAN sniffer to confirm valid CAN traffic. Look for constant dominant state (short) or excessive errors.
  7. Measure termination resistance across CAN_H and CAN_L with key off. Replace missing/failed terminators if resistance not near expected (~60 ohms).
  8. If bus activity absent only at the module node, disconnect the module and check if other nodes return to normal communication. If disconnecting restores bus, suspect internal short in the module.
  9. If wiring fault suspected, perform wiring continuity and short-to-power/ground tests between module and junctions/gateway. Repair wiring harness as needed.
  10. If wiring and power/ground are good but module is unresponsive, attempt module reset (clear codes) and reflash/update software per OEM guidance. Re-test communications.
  11. Replace the interior lighting control module only after verifying power, ground and network integrity. After replacement, reprogram/configure and clear codes. Verify function and absence of U02BF.

Likely causes

  • Blown fuse or disconnected power/ground to the lighting module
  • Damaged connector or corrosion at the module harness
  • Short to battery or ground on CAN_H or CAN_L wiring
  • Module internal failure (dead or unresponsive)
  • Faulty gateway or body control module preventing messages from being seen

Fault status

⚠️ Status
Lost Communication With Interior Lighting Control Module B — expected network messages from the Interior Lighting Control Module B were not received by the vehicle network/gateway.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-4.0 hours

Similar codes

U0100 U0121 U0140 U0155 U0243
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