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Home / DTC / B1171 — Body Control Module Communication Fault

B1171 — Body Control Module Communication Fault

Detailed page for trouble code B1171.

34,405codes
59brands
11,914generic
22,491specific
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Code

B1171

HUMMER B — Body

Body Control Module Communication Fault

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

Causes

  • Low or intermittent battery voltage or poor battery connection
  • Blown fuse or faulty power/relay feeding the BCM
  • Poor or corroded ground at the BCM or chassis
  • Damaged, chafed, or disconnected communication wiring (CAN/LIN) or connectors
  • Water intrusion or corrosion at the BCM connector or harness
  • Faulty BCM (internal electronics)

Symptoms

  • Instrument panel or DIC (Driver Information Center) shows communication or module warnings
  • Some BCM-controlled functions inoperative (locks, lighting, wipers, HVAC, remote keyless)
  • Intermittent or permanent electrical gremlins that come and go with vehicle vibration or temperature
  • Multiple modules reporting communication-related DTCs
  • No response from BCM to a scan tool or intermittent scan tool communication failures
  • Vehicle may enter reduced functionality or limp modes for systems relying on BCM messages

What to check

  • Connect a capable scan tool and record all DTCs and freeze frame data; note time and conditions of failure
  • Confirm battery state of charge and test battery terminals for corrosion and tightness
  • Verify fuses and relays for BCM power and accessory supplies are present and good
  • Visually inspect BCM and surrounding harness for water damage, corrosion, pinch points, or repairs
  • Inspect and wiggle CAN/LIN connectors and harnesses with ignition on while monitoring network for errors (use scope or scan tool bus data)
  • Measure BCM supply voltage and ground(s) with a DVOM with ignition ON and key OFF; check for consistent voltage under load

Signal parameters

  • Battery voltage at BCM: nominal 12 V (expected 11–14.5 V during normal operation)
  • BCM power supply pin(s) present and stable at ignition ON/ACC (within battery range)
  • Ground resistance: BCM chassis ground < 0.1–0.2 ohm ideally; continuity to chassis metal good
  • CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each referenced to chassis), differential ≈ 0 V at recessive state
  • CAN bus dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V) when messages are driven
  • Bus termination resistance between CAN_H and CAN_L ≈ 60 ohms (two 120-ohm terminators in parallel)

Diagnostic algorithm

  1. Safety first: battery support or stable battery condition recommended when performing extended diagnostics; note anti-theft requirements before disconnecting modules.
  2. Step 1 — Retrieve codes: Use manufacturer-capable scan tool, record B1171 and any related U/B codes plus freeze frame data and module present/absent lists.
  3. Step 2 — Verify basics: Check battery state, main power distribution fuses and BCM supply/ignition fuses; repair/replace as needed.
  4. Step 3 — Inspect connectors/harness: Visually inspect BCM connectors for bent/corroded pins, water intrusion, or heat damage. Repair corrosion or damaged terminals.
  5. Step 4 — Check grounds and supply: Measure supply voltage and ground continuity at BCM; repair high resistance or intermittent grounds.
  6. Step 5 — Monitor network: With scan tool and/or oscilloscope monitor CAN_H/CAN_L while operating or while re-creating failure. Look for missing messages, dominant bus-off, voltage shorts, or excessive noise.
  7. Step 6 — Isolate faults: Disconnect suspect modules or segments to determine if another device is holding the bus dominant or flooding messages. Repair or isolate the offending circuit.
  8. Step 7 — Repair wiring: If open/short/high-resistance wiring is found, repair with proper connectors and sealing. Replace damaged pigtails or harness sections; solder/heat-shrink or use approved crimp joints.
  9. Step 8 — Clear codes and retest: After repairs, clear DTCs and verify the fault does not return under the same conditions and that all modules communicate normally.
  10. Step 9 — BCM replacement/programming: Only replace the BCM after verifying wiring and network health. Install a new or reconditioned BCM and program/configure with manufacturer software per procedure. Verify security/anti-theft relearn steps if required.
  11. Step 10 — Final verification: Road test to ensure intermittent symptoms are resolved and no further network faults appear; re-scan all modules.

Likely causes

  • Corroded BCM connector or pins allowing intermittent contact
  • Open or high-resistance ground to BCM
  • Shorted or open CANH/CANL wires near BCM or junction points
  • Blown fuse or relay supplying BCM memory/power circuits
  • Aftermarket accessory tied into body circuits without proper termination causing bus errors
  • BCM internal failure following water intrusion or electrical surge

Fault status

⚠️ Status
BCM detected loss or corruption of communication on the vehicle network. The module has logged a communication fault (B1171) and may report other related network codes. Fault may be intermittent or persistent.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0073 U0140 B1170 B1263
Repair manuals

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Code

B1171

LAND ROVER B — Body

Handle driver's door internal

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

Causes

  • Low or intermittent battery voltage or poor battery connection
  • Blown fuse or faulty power/relay feeding the BCM
  • Poor or corroded ground at the BCM or chassis
  • Damaged, chafed, or disconnected communication wiring (CAN/LIN) or connectors
  • Water intrusion or corrosion at the BCM connector or harness
  • Faulty BCM (internal electronics)

Symptoms

  • Instrument panel or DIC (Driver Information Center) shows communication or module warnings
  • Some BCM-controlled functions inoperative (locks, lighting, wipers, HVAC, remote keyless)
  • Intermittent or permanent electrical gremlins that come and go with vehicle vibration or temperature
  • Multiple modules reporting communication-related DTCs
  • No response from BCM to a scan tool or intermittent scan tool communication failures
  • Vehicle may enter reduced functionality or limp modes for systems relying on BCM messages

What to check

  • Connect a capable scan tool and record all DTCs and freeze frame data; note time and conditions of failure
  • Confirm battery state of charge and test battery terminals for corrosion and tightness
  • Verify fuses and relays for BCM power and accessory supplies are present and good
  • Visually inspect BCM and surrounding harness for water damage, corrosion, pinch points, or repairs
  • Inspect and wiggle CAN/LIN connectors and harnesses with ignition on while monitoring network for errors (use scope or scan tool bus data)
  • Measure BCM supply voltage and ground(s) with a DVOM with ignition ON and key OFF; check for consistent voltage under load

Signal parameters

  • Battery voltage at BCM: nominal 12 V (expected 11–14.5 V during normal operation)
  • BCM power supply pin(s) present and stable at ignition ON/ACC (within battery range)
  • Ground resistance: BCM chassis ground < 0.1–0.2 ohm ideally; continuity to chassis metal good
  • CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each referenced to chassis), differential ≈ 0 V at recessive state
  • CAN bus dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V) when messages are driven
  • Bus termination resistance between CAN_H and CAN_L ≈ 60 ohms (two 120-ohm terminators in parallel)

Diagnostic algorithm

  1. Safety first: battery support or stable battery condition recommended when performing extended diagnostics; note anti-theft requirements before disconnecting modules.
  2. Step 1 — Retrieve codes: Use manufacturer-capable scan tool, record B1171 and any related U/B codes plus freeze frame data and module present/absent lists.
  3. Step 2 — Verify basics: Check battery state, main power distribution fuses and BCM supply/ignition fuses; repair/replace as needed.
  4. Step 3 — Inspect connectors/harness: Visually inspect BCM connectors for bent/corroded pins, water intrusion, or heat damage. Repair corrosion or damaged terminals.
  5. Step 4 — Check grounds and supply: Measure supply voltage and ground continuity at BCM; repair high resistance or intermittent grounds.
  6. Step 5 — Monitor network: With scan tool and/or oscilloscope monitor CAN_H/CAN_L while operating or while re-creating failure. Look for missing messages, dominant bus-off, voltage shorts, or excessive noise.
  7. Step 6 — Isolate faults: Disconnect suspect modules or segments to determine if another device is holding the bus dominant or flooding messages. Repair or isolate the offending circuit.
  8. Step 7 — Repair wiring: If open/short/high-resistance wiring is found, repair with proper connectors and sealing. Replace damaged pigtails or harness sections; solder/heat-shrink or use approved crimp joints.
  9. Step 8 — Clear codes and retest: After repairs, clear DTCs and verify the fault does not return under the same conditions and that all modules communicate normally.
  10. Step 9 — BCM replacement/programming: Only replace the BCM after verifying wiring and network health. Install a new or reconditioned BCM and program/configure with manufacturer software per procedure. Verify security/anti-theft relearn steps if required.
  11. Step 10 — Final verification: Road test to ensure intermittent symptoms are resolved and no further network faults appear; re-scan all modules.

Likely causes

  • Corroded BCM connector or pins allowing intermittent contact
  • Open or high-resistance ground to BCM
  • Shorted or open CANH/CANL wires near BCM or junction points
  • Blown fuse or relay supplying BCM memory/power circuits
  • Aftermarket accessory tied into body circuits without proper termination causing bus errors
  • BCM internal failure following water intrusion or electrical surge

Fault status

⚠️ Status
BCM detected loss or corruption of communication on the vehicle network. The module has logged a communication fault (B1171) and may report other related network codes. Fault may be intermittent or persistent.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0073 U0140 B1170 B1263
320

Browse 320 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

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

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