Code
U0142
Generic
U — Network/User
Lost Communication With Body Control Module B
Views:
UK: 23
EN: 34
RU: 31
AI status
Completed
Completed
100%
Causes
- BCM B power supply fault (blown fuse, lost battery feed)
- BCM B ground open or high resistance ground
- Damaged or corroded BCM connector or pins
- Broken or shorted CAN/LIN wiring between BCM B and network
- Failed BCM B (hardware or internal firmware fault)
- Network termination or bus wiring fault (open, short to battery/ground)
Symptoms
- Malfunction indicator lamp (MIL) or network warning lamp may be on
- Functions controlled by BCM B not available or intermittent (locks, interior lights, wipers, convenience functions depending on vehicle)
- Scan tool reports U0142 and shows BCM B not present or unable to connect
- Other modules report related communication trouble codes or bus-off conditions
- Intermittent loss of multiple convenience systems
- Vehicle may show gateway/module errors on dash
What to check
- Connect a capable OBD-II scan tool and verify U0142 and any related U-codes; record freeze frame and module list
- Verify battery voltage (≥12.4 V recommended) and note any recent battery disconnects
- Check BCM B fuses and relays for continuity and proper operation
- Visually inspect BCM connector for corrosion, bent pins, damage or water intrusion
- Check chassis and engine grounds associated with BCM B for tightness and cleanliness
- Inspect CAN wiring and harnesses for physical damage, rodent bites or pinched sections
Signal parameters
- Typical CAN recessive voltages (idle): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (common-mode ~2.5 V)
- Typical CAN dominant voltages: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Differential voltage during active frames ≈ 1.5–2.5 V depending on network and transceivers
- Bus termination resistance ≈ 60 ohms measured between CAN_H and CAN_L at vehicle end-to-end (two 120 Ω terminators in parallel)
- BCM supply voltage (key on): ~12 V (vehicle-specific), ground resistance ideally
- Network baud rate is vehicle-dependent (commonly 250 kbps or 500 kbps); verify correct speed before using analyzers
Diagnostic algorithm
- Verify and record code(s): clear codes and attempt to reproduce; note whether U0142 returns and whether it is permanent or intermittent.
- Confirm BCM presence: use scan tool to list modules; if BCM B not listed, proceed to electrical checks.
- Check vehicle battery state and top-off if low; ensure stable power during tests.
- Check fuses/relays feeding BCM B for continuity and correct supply voltage with key on and off.
- Inspect BCM connector and harness for corrosion, bent pins, water ingress and repair or reseal as needed.
- Verify BCM ground points are clean and tight; measure voltage drop while cranking/accessing loads if needed.
- Measure CAN bus voltages at the BCM connector (backprobe): check recessive voltages, then observe for activity while operating relevant systems. Compare to expected signal_params.
- Measure termination resistance between CAN_H and CAN_L across the network (~60 Ω). If open or far from expected, trace wiring for broken wires or missing terminator.
- If bus is shorted to battery/ground, isolate segments by disconnecting connectors/modules one at a time to find the offending section.
- Disconnect aftermarket accessories that tie into vehicle power or networks and re-check communication.
- If wiring and supplies are good but BCM remains unresponsive, attempt communication via a known-good diagnostic interface; check for available software updates or reflash procedure from OEM.
- If reprogramming is required and wiring/power checks pass but module still fails, replace BCM per manufacturer procedure and perform module pairing/initialization and relearn operations as required.
Likely causes
- Loose/corroded BCM connector or poor ground at BCM
- Open or shorted CAN high/low wiring near BCM or at common splice
- Blown fuse or lost key-on power feed to BCM B
- BCM B internal failure or corrupted software
- Aftermarket alarm, radio or module incorrectly tied into network
Fault status
Status
Stored when the vehicle communication bus does not receive/respond from Body Control Module B or when the module fails to respond to diagnostic requests. Indicates lost communication, not a specific component function failure.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
U0142
HYUNDAI
U — Network/User
Lost Communication With Body Control Module “B”
Views:
UK: 16
EN: 22
RU: 30
AI status
Completed
Completed
100%
Causes
- BCM B power supply fault (blown fuse, lost battery feed)
- BCM B ground open or high resistance ground
- Damaged or corroded BCM connector or pins
- Broken or shorted CAN/LIN wiring between BCM B and network
- Failed BCM B (hardware or internal firmware fault)
- Network termination or bus wiring fault (open, short to battery/ground)
Symptoms
- Malfunction indicator lamp (MIL) or network warning lamp may be on
- Functions controlled by BCM B not available or intermittent (locks, interior lights, wipers, convenience functions depending on vehicle)
- Scan tool reports U0142 and shows BCM B not present or unable to connect
- Other modules report related communication trouble codes or bus-off conditions
- Intermittent loss of multiple convenience systems
- Vehicle may show gateway/module errors on dash
What to check
- Connect a capable OBD-II scan tool and verify U0142 and any related U-codes; record freeze frame and module list
- Verify battery voltage (≥12.4 V recommended) and note any recent battery disconnects
- Check BCM B fuses and relays for continuity and proper operation
- Visually inspect BCM connector for corrosion, bent pins, damage or water intrusion
- Check chassis and engine grounds associated with BCM B for tightness and cleanliness
- Inspect CAN wiring and harnesses for physical damage, rodent bites or pinched sections
Signal parameters
- Typical CAN recessive voltages (idle): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (common-mode ~2.5 V)
- Typical CAN dominant voltages: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Differential voltage during active frames ≈ 1.5–2.5 V depending on network and transceivers
- Bus termination resistance ≈ 60 ohms measured between CAN_H and CAN_L at vehicle end-to-end (two 120 Ω terminators in parallel)
- BCM supply voltage (key on): ~12 V (vehicle-specific), ground resistance ideally
- Network baud rate is vehicle-dependent (commonly 250 kbps or 500 kbps); verify correct speed before using analyzers
Diagnostic algorithm
- Verify and record code(s): clear codes and attempt to reproduce; note whether U0142 returns and whether it is permanent or intermittent.
- Confirm BCM presence: use scan tool to list modules; if BCM B not listed, proceed to electrical checks.
- Check vehicle battery state and top-off if low; ensure stable power during tests.
- Check fuses/relays feeding BCM B for continuity and correct supply voltage with key on and off.
- Inspect BCM connector and harness for corrosion, bent pins, water ingress and repair or reseal as needed.
- Verify BCM ground points are clean and tight; measure voltage drop while cranking/accessing loads if needed.
- Measure CAN bus voltages at the BCM connector (backprobe): check recessive voltages, then observe for activity while operating relevant systems. Compare to expected signal_params.
- Measure termination resistance between CAN_H and CAN_L across the network (~60 Ω). If open or far from expected, trace wiring for broken wires or missing terminator.
- If bus is shorted to battery/ground, isolate segments by disconnecting connectors/modules one at a time to find the offending section.
- Disconnect aftermarket accessories that tie into vehicle power or networks and re-check communication.
- If wiring and supplies are good but BCM remains unresponsive, attempt communication via a known-good diagnostic interface; check for available software updates or reflash procedure from OEM.
- If reprogramming is required and wiring/power checks pass but module still fails, replace BCM per manufacturer procedure and perform module pairing/initialization and relearn operations as required.
Likely causes
- Loose/corroded BCM connector or poor ground at BCM
- Open or shorted CAN high/low wiring near BCM or at common splice
- Blown fuse or lost key-on power feed to BCM B
- BCM B internal failure or corrupted software
- Aftermarket alarm, radio or module incorrectly tied into network
Fault status
Status
Stored when the vehicle communication bus does not receive/respond from Body Control Module B or when the module fails to respond to diagnostic requests. Indicates lost communication, not a specific component function failure.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
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Code
U0142
LAND ROVER
U — Network/User
Lost communication with the body control module B
Views:
UK: 11
EN: 18
RU: 19
AI status
Completed
Completed
100%
Causes
- BCM B power supply fault (blown fuse, lost battery feed)
- BCM B ground open or high resistance ground
- Damaged or corroded BCM connector or pins
- Broken or shorted CAN/LIN wiring between BCM B and network
- Failed BCM B (hardware or internal firmware fault)
- Network termination or bus wiring fault (open, short to battery/ground)
Symptoms
- Malfunction indicator lamp (MIL) or network warning lamp may be on
- Functions controlled by BCM B not available or intermittent (locks, interior lights, wipers, convenience functions depending on vehicle)
- Scan tool reports U0142 and shows BCM B not present or unable to connect
- Other modules report related communication trouble codes or bus-off conditions
- Intermittent loss of multiple convenience systems
- Vehicle may show gateway/module errors on dash
What to check
- Connect a capable OBD-II scan tool and verify U0142 and any related U-codes; record freeze frame and module list
- Verify battery voltage (≥12.4 V recommended) and note any recent battery disconnects
- Check BCM B fuses and relays for continuity and proper operation
- Visually inspect BCM connector for corrosion, bent pins, damage or water intrusion
- Check chassis and engine grounds associated with BCM B for tightness and cleanliness
- Inspect CAN wiring and harnesses for physical damage, rodent bites or pinched sections
Signal parameters
- Typical CAN recessive voltages (idle): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (common-mode ~2.5 V)
- Typical CAN dominant voltages: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Differential voltage during active frames ≈ 1.5–2.5 V depending on network and transceivers
- Bus termination resistance ≈ 60 ohms measured between CAN_H and CAN_L at vehicle end-to-end (two 120 Ω terminators in parallel)
- BCM supply voltage (key on): ~12 V (vehicle-specific), ground resistance ideally
- Network baud rate is vehicle-dependent (commonly 250 kbps or 500 kbps); verify correct speed before using analyzers
Diagnostic algorithm
- Verify and record code(s): clear codes and attempt to reproduce; note whether U0142 returns and whether it is permanent or intermittent.
- Confirm BCM presence: use scan tool to list modules; if BCM B not listed, proceed to electrical checks.
- Check vehicle battery state and top-off if low; ensure stable power during tests.
- Check fuses/relays feeding BCM B for continuity and correct supply voltage with key on and off.
- Inspect BCM connector and harness for corrosion, bent pins, water ingress and repair or reseal as needed.
- Verify BCM ground points are clean and tight; measure voltage drop while cranking/accessing loads if needed.
- Measure CAN bus voltages at the BCM connector (backprobe): check recessive voltages, then observe for activity while operating relevant systems. Compare to expected signal_params.
- Measure termination resistance between CAN_H and CAN_L across the network (~60 Ω). If open or far from expected, trace wiring for broken wires or missing terminator.
- If bus is shorted to battery/ground, isolate segments by disconnecting connectors/modules one at a time to find the offending section.
- Disconnect aftermarket accessories that tie into vehicle power or networks and re-check communication.
- If wiring and supplies are good but BCM remains unresponsive, attempt communication via a known-good diagnostic interface; check for available software updates or reflash procedure from OEM.
- If reprogramming is required and wiring/power checks pass but module still fails, replace BCM per manufacturer procedure and perform module pairing/initialization and relearn operations as required.
Likely causes
- Loose/corroded BCM connector or poor ground at BCM
- Open or shorted CAN high/low wiring near BCM or at common splice
- Blown fuse or lost key-on power feed to BCM B
- BCM B internal failure or corrupted software
- Aftermarket alarm, radio or module incorrectly tied into network
Fault status
Status
Stored when the vehicle communication bus does not receive/respond from Body Control Module B or when the module fails to respond to diagnostic requests. Indicates lost communication, not a specific component function failure.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Repair manuals for LAND ROVER
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Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop Manual199,00 UAH
Land Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop Manual199,00 UAH
Land Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)
Workshop Manual199,00 UAH
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
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0
Send to email