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Home / DTC / B1115 — Body Control Module (BCM) Communication Fault

B1115 — Body Control Module (BCM) Communication Fault

Detailed page for trouble code B1115.

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Code

B1115

HUMMER B — Body

Body Control Module (BCM) Communication Fault

Brand: HUMMER
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open, short or high resistance in CAN/communication wiring or connectors
  • Poor battery voltage or poor ground to BCM
  • Blown fuse or faulty power/ignition feed to BCM
  • Faulty BCM or other module pulling the bus down
  • Corroded or water-damaged connector at BCM or junctions
  • Aftermarket electrical accessories incorrectly installed

Symptoms

  • Multiple body functions intermittent or inoperative (door locks, interior lights, wipers, windows)
  • Warning lamps or messages related to communication faults
  • Erratic operation of modules that rely on BCM messages
  • Modules appear 'asleep' or do not respond to scan tool
  • Codes for lost communication with other modules (U-codes) may be present

What to check

  • Use a scan tool to read all stored/active DTCs and freeze frame; note time and ignition state
  • Verify good battery voltage (12.4–12.9 V at rest, >13 V with engine running) and clean battery terminals
  • Inspect BCM connectors and harness for corrosion, bent pins, water intrusion, or damage
  • Check BCM power and ground circuits, and verify fuses/relays for BCM power feed
  • Check for other communication-related U-codes that identify affected modules
  • Measure CAN bus voltages with key on, engine off (see signal parameters) and check for proper idle levels and differential

Signal parameters

  • Battery voltage: ~12.4–12.9 V resting, >13 V with engine running
  • BCM power feed: near battery voltage with key on
  • BCM ground:
  • CAN bus idle voltages (node-level): CAN_H ~2.5 V, CAN_L ~2.5 V (approx.); differential idle ≈ 0 V - both sit near 2.5 V
  • CAN bus dominant state: CAN_H ~3.5 V, CAN_L ~1.5 V when messages are transmitted (verify with scope)
  • Bus bit-rate and waveform should be clean with no excessive ringing or stuck dominant bits

Diagnostic algorithm

  1. Record all DTCs and freeze frame data with a capable scan tool; note ignition state and recurring patterns.
  2. Verify battery condition and BCM supply/ground voltages; repair any low-voltage or poor-ground issues and recheck.
  3. Inspect BCM connector and harness visually for damage, corrosion, or water ingress; repair or reseal as needed.
  4. Check BCM power fuses and relays; replace if blown and evaluate cause of blown protection devices.
  5. Check for related U-codes that indicate which modules have lost communication to narrow the faulted network segment.
  6. Measure CAN_H and CAN_L at BCM with key ON, engine OFF. If voltages are out of expected ranges, isolate wiring for short/open.
  7. Use an oscilloscope to view CAN waveforms to identify collisions, stuck dominant bits, or intermittent noise; perform wiggle tests on harness.
  8. Disconnect non-essential modules or suspect nodes (one at a time) to see if the network recovers; this can identify a shorting node.
  9. If wiring and external modules check good and bus signals are correct, suspect BCM internal transceiver or internal failure—verify with manufacturer service data.
  10. If BCM replacement is required, follow OEM procedures for replacement, programming and configuration; clear codes and confirm repair by road test and re-scan.

Likely causes

  • Damaged CAN High or CAN Low wiring near BCM or harness chafe
  • Loose or corroded BCM ground or battery terminal
  • Blown BCM power fuse or fusible link
  • Failed BCM internal transceiver
  • Intermittent short to battery or ground from an accessory

Fault status

⚠️ Status
BCM Communication Fault — loss or interruption of network messages to/from the Body Control Module. Further electrical and network diagnostics required.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-4.0 hours

Similar codes

U0073 U0100 U0155 U0121 B1110
Repair manuals

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Code

B1115

LAND ROVER B — Body

high mounted stoplamp control

Brand: LAND ROVER
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open, short or high resistance in CAN/communication wiring or connectors
  • Poor battery voltage or poor ground to BCM
  • Blown fuse or faulty power/ignition feed to BCM
  • Faulty BCM or other module pulling the bus down
  • Corroded or water-damaged connector at BCM or junctions
  • Aftermarket electrical accessories incorrectly installed

Symptoms

  • Multiple body functions intermittent or inoperative (door locks, interior lights, wipers, windows)
  • Warning lamps or messages related to communication faults
  • Erratic operation of modules that rely on BCM messages
  • Modules appear 'asleep' or do not respond to scan tool
  • Codes for lost communication with other modules (U-codes) may be present

What to check

  • Use a scan tool to read all stored/active DTCs and freeze frame; note time and ignition state
  • Verify good battery voltage (12.4–12.9 V at rest, >13 V with engine running) and clean battery terminals
  • Inspect BCM connectors and harness for corrosion, bent pins, water intrusion, or damage
  • Check BCM power and ground circuits, and verify fuses/relays for BCM power feed
  • Check for other communication-related U-codes that identify affected modules
  • Measure CAN bus voltages with key on, engine off (see signal parameters) and check for proper idle levels and differential

Signal parameters

  • Battery voltage: ~12.4–12.9 V resting, >13 V with engine running
  • BCM power feed: near battery voltage with key on
  • BCM ground:
  • CAN bus idle voltages (node-level): CAN_H ~2.5 V, CAN_L ~2.5 V (approx.); differential idle ≈ 0 V - both sit near 2.5 V
  • CAN bus dominant state: CAN_H ~3.5 V, CAN_L ~1.5 V when messages are transmitted (verify with scope)
  • Bus bit-rate and waveform should be clean with no excessive ringing or stuck dominant bits

Diagnostic algorithm

  1. Record all DTCs and freeze frame data with a capable scan tool; note ignition state and recurring patterns.
  2. Verify battery condition and BCM supply/ground voltages; repair any low-voltage or poor-ground issues and recheck.
  3. Inspect BCM connector and harness visually for damage, corrosion, or water ingress; repair or reseal as needed.
  4. Check BCM power fuses and relays; replace if blown and evaluate cause of blown protection devices.
  5. Check for related U-codes that indicate which modules have lost communication to narrow the faulted network segment.
  6. Measure CAN_H and CAN_L at BCM with key ON, engine OFF. If voltages are out of expected ranges, isolate wiring for short/open.
  7. Use an oscilloscope to view CAN waveforms to identify collisions, stuck dominant bits, or intermittent noise; perform wiggle tests on harness.
  8. Disconnect non-essential modules or suspect nodes (one at a time) to see if the network recovers; this can identify a shorting node.
  9. If wiring and external modules check good and bus signals are correct, suspect BCM internal transceiver or internal failure—verify with manufacturer service data.
  10. If BCM replacement is required, follow OEM procedures for replacement, programming and configuration; clear codes and confirm repair by road test and re-scan.

Likely causes

  • Damaged CAN High or CAN Low wiring near BCM or harness chafe
  • Loose or corroded BCM ground or battery terminal
  • Blown BCM power fuse or fusible link
  • Failed BCM internal transceiver
  • Intermittent short to battery or ground from an accessory

Fault status

⚠️ Status
BCM Communication Fault — loss or interruption of network messages to/from the Body Control Module. Further electrical and network diagnostics required.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-4.0 hours

Similar codes

U0073 U0100 U0155 U0121 B1110
266

Browse 266 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

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