Code
U0014
Generic
U — Network/User
Medium Speed CAN Communication Bus (+) High
Views:
UK: 30
EN: 44
RU: 29
AI status
Completed
Completed
100%
Causes
- Short to battery/ignition voltage on CAN (+) conductor
- Failed CAN transceiver in one or more control modules
- Damaged wiring harness or chafed/shorted conductor
- Poor/loose/corroded connector terminals
- Faulty termination resistor or improper termination
- Aftermarket accessories incorrectly connected to the CAN circuit
Symptoms
- MIL or network-related warning lamps illuminated
- Loss of communication with one or more body/control modules on medium-speed CAN
- Intermittent or complete failure of systems tied to that bus (e.g., HVAC, doors, keyless entry, instrument cluster messages)
- Possible increased battery drain if a module is powering the bus
- Erratic or frozen module operation for devices on the medium-speed CAN
What to check
- Read and record all U‑codes and freeze frame data with a capable scan tool
- Visually inspect CAN wiring, connectors and harness near modules and along routing for damage, pin corrosion, or shorts
- Measure DC voltage between CAN (+) and vehicle ground with ignition ON; compare to expected idle range
- Measure DC voltage between CAN (+) and CAN (−) and between CAN (−) and ground
- Check continuity and resistance of CAN bus termination (expect roughly 60 Ω across CAN+ and CAN− with key ON and no modules disconnected)
- Use a lab scope to view CAN waveform for bus idle level, dominant level and high-voltage spikes
Signal parameters
- Normal idle common-mode bus voltage: approx. 2.5 V (both lines close to this)
- Normal dominant state differential: CAN+ rises and CAN− falls to create ~2.0 V differential
- Abnormal/high condition: CAN (+) sustained above ~3.5–4.0 V suggests short to battery or stuck driver
- Expected termination resistance: ~60 Ω across CAN+ and CAN− (two 120 Ω in parallel typical)
- Use oscilloscope for: clean recessive waveform (~2.5 V), clear dominant transitions, absence of sustained DC offset or high-voltage spikes
Diagnostic algorithm
- Record trouble codes and freeze-frame data; note which modules report loss of communication.
- Visually inspect connectors and wiring along the medium-speed CAN circuit, especially near recent service areas and where harnesses flex.
- With ignition ON (engine off), measure CAN(+) to ground and CAN(−) to ground at a convenient connector. Compare to expected idle values.
- Measure resistance across CAN+ and CAN− with ignition ON; verify ~60 Ω. If open or very low, isolate cause.
- Use a lab scope to examine the CAN(+) waveform for sustained high voltage, missing recessive level, or abnormal noise/spikes.
- If CAN(+) is high, systematically isolate by disconnecting modules on that bus one at a time (start with easily accessible body modules) until the voltage returns to normal or the code clears. Note which disconnect changes the condition.
- If disconnecting a module clears the fault, suspect that module’s transceiver or its power/ground circuits; inspect and test the module and replace if necessary.
- If no module isolation locates the fault, inspect harness for a short to battery. Repair wiring or connector faults and retest.
- After repairs, clear codes and road/test to confirm the fault does not return. Re-scan to verify communication restored to all modules.
Likely causes
- Short to constant or switched 12 V at CAN (+) due to chafed wire or pin contact
- Faulty module transceiver driving CAN (+) high (common failure in modules with internal drivers)
- Connector corrosion or bent pins causing voltage feed-through
- Missing or open CAN termination causing abnormal bus biasing
- Recent repairs or aftermarket installations that tapped into CAN wiring
Fault status
Status
Medium-speed CAN (+) circuit voltage is higher than expected, causing loss/degradation of communication on the medium-speed CAN bus. Possible short to battery or a module driving the bus high.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
U0014
HYUNDAI
U — Network/User
Medium Speed CAN Communication Bus (+) High
Views:
UK: 21
EN: 26
RU: 27
AI status
Completed
Completed
100%
Causes
- Short to battery/ignition voltage on CAN (+) conductor
- Failed CAN transceiver in one or more control modules
- Damaged wiring harness or chafed/shorted conductor
- Poor/loose/corroded connector terminals
- Faulty termination resistor or improper termination
- Aftermarket accessories incorrectly connected to the CAN circuit
Symptoms
- MIL or network-related warning lamps illuminated
- Loss of communication with one or more body/control modules on medium-speed CAN
- Intermittent or complete failure of systems tied to that bus (e.g., HVAC, doors, keyless entry, instrument cluster messages)
- Possible increased battery drain if a module is powering the bus
- Erratic or frozen module operation for devices on the medium-speed CAN
What to check
- Read and record all U‑codes and freeze frame data with a capable scan tool
- Visually inspect CAN wiring, connectors and harness near modules and along routing for damage, pin corrosion, or shorts
- Measure DC voltage between CAN (+) and vehicle ground with ignition ON; compare to expected idle range
- Measure DC voltage between CAN (+) and CAN (−) and between CAN (−) and ground
- Check continuity and resistance of CAN bus termination (expect roughly 60 Ω across CAN+ and CAN− with key ON and no modules disconnected)
- Use a lab scope to view CAN waveform for bus idle level, dominant level and high-voltage spikes
Signal parameters
- Normal idle common-mode bus voltage: approx. 2.5 V (both lines close to this)
- Normal dominant state differential: CAN+ rises and CAN− falls to create ~2.0 V differential
- Abnormal/high condition: CAN (+) sustained above ~3.5–4.0 V suggests short to battery or stuck driver
- Expected termination resistance: ~60 Ω across CAN+ and CAN− (two 120 Ω in parallel typical)
- Use oscilloscope for: clean recessive waveform (~2.5 V), clear dominant transitions, absence of sustained DC offset or high-voltage spikes
Diagnostic algorithm
- Record trouble codes and freeze-frame data; note which modules report loss of communication.
- Visually inspect connectors and wiring along the medium-speed CAN circuit, especially near recent service areas and where harnesses flex.
- With ignition ON (engine off), measure CAN(+) to ground and CAN(−) to ground at a convenient connector. Compare to expected idle values.
- Measure resistance across CAN+ and CAN− with ignition ON; verify ~60 Ω. If open or very low, isolate cause.
- Use a lab scope to examine the CAN(+) waveform for sustained high voltage, missing recessive level, or abnormal noise/spikes.
- If CAN(+) is high, systematically isolate by disconnecting modules on that bus one at a time (start with easily accessible body modules) until the voltage returns to normal or the code clears. Note which disconnect changes the condition.
- If disconnecting a module clears the fault, suspect that module’s transceiver or its power/ground circuits; inspect and test the module and replace if necessary.
- If no module isolation locates the fault, inspect harness for a short to battery. Repair wiring or connector faults and retest.
- After repairs, clear codes and road/test to confirm the fault does not return. Re-scan to verify communication restored to all modules.
Likely causes
- Short to constant or switched 12 V at CAN (+) due to chafed wire or pin contact
- Faulty module transceiver driving CAN (+) high (common failure in modules with internal drivers)
- Connector corrosion or bent pins causing voltage feed-through
- Missing or open CAN termination causing abnormal bus biasing
- Recent repairs or aftermarket installations that tapped into CAN wiring
Fault status
Status
Medium-speed CAN (+) circuit voltage is higher than expected, causing loss/degradation of communication on the medium-speed CAN bus. Possible short to battery or a module driving the bus high.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
U0014
LAND ROVER
U — Network/User
Medium speed CAN communication bus (+) high
Views:
UK: 17
EN: 27
RU: 23
AI status
Completed
Completed
100%
Causes
- Short to battery/ignition voltage on CAN (+) conductor
- Failed CAN transceiver in one or more control modules
- Damaged wiring harness or chafed/shorted conductor
- Poor/loose/corroded connector terminals
- Faulty termination resistor or improper termination
- Aftermarket accessories incorrectly connected to the CAN circuit
Symptoms
- MIL or network-related warning lamps illuminated
- Loss of communication with one or more body/control modules on medium-speed CAN
- Intermittent or complete failure of systems tied to that bus (e.g., HVAC, doors, keyless entry, instrument cluster messages)
- Possible increased battery drain if a module is powering the bus
- Erratic or frozen module operation for devices on the medium-speed CAN
What to check
- Read and record all U‑codes and freeze frame data with a capable scan tool
- Visually inspect CAN wiring, connectors and harness near modules and along routing for damage, pin corrosion, or shorts
- Measure DC voltage between CAN (+) and vehicle ground with ignition ON; compare to expected idle range
- Measure DC voltage between CAN (+) and CAN (−) and between CAN (−) and ground
- Check continuity and resistance of CAN bus termination (expect roughly 60 Ω across CAN+ and CAN− with key ON and no modules disconnected)
- Use a lab scope to view CAN waveform for bus idle level, dominant level and high-voltage spikes
Signal parameters
- Normal idle common-mode bus voltage: approx. 2.5 V (both lines close to this)
- Normal dominant state differential: CAN+ rises and CAN− falls to create ~2.0 V differential
- Abnormal/high condition: CAN (+) sustained above ~3.5–4.0 V suggests short to battery or stuck driver
- Expected termination resistance: ~60 Ω across CAN+ and CAN− (two 120 Ω in parallel typical)
- Use oscilloscope for: clean recessive waveform (~2.5 V), clear dominant transitions, absence of sustained DC offset or high-voltage spikes
Diagnostic algorithm
- Record trouble codes and freeze-frame data; note which modules report loss of communication.
- Visually inspect connectors and wiring along the medium-speed CAN circuit, especially near recent service areas and where harnesses flex.
- With ignition ON (engine off), measure CAN(+) to ground and CAN(−) to ground at a convenient connector. Compare to expected idle values.
- Measure resistance across CAN+ and CAN− with ignition ON; verify ~60 Ω. If open or very low, isolate cause.
- Use a lab scope to examine the CAN(+) waveform for sustained high voltage, missing recessive level, or abnormal noise/spikes.
- If CAN(+) is high, systematically isolate by disconnecting modules on that bus one at a time (start with easily accessible body modules) until the voltage returns to normal or the code clears. Note which disconnect changes the condition.
- If disconnecting a module clears the fault, suspect that module’s transceiver or its power/ground circuits; inspect and test the module and replace if necessary.
- If no module isolation locates the fault, inspect harness for a short to battery. Repair wiring or connector faults and retest.
- After repairs, clear codes and road/test to confirm the fault does not return. Re-scan to verify communication restored to all modules.
Likely causes
- Short to constant or switched 12 V at CAN (+) due to chafed wire or pin contact
- Faulty module transceiver driving CAN (+) high (common failure in modules with internal drivers)
- Connector corrosion or bent pins causing voltage feed-through
- Missing or open CAN termination causing abnormal bus biasing
- Recent repairs or aftermarket installations that tapped into CAN wiring
Fault status
Status
Medium-speed CAN (+) circuit voltage is higher than expected, causing loss/degradation of communication on the medium-speed CAN bus. Possible short to battery or a module driving the bus high.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
U0014
MERCEDES-BENZ
U — Network/User
Medium Speed CAN Communication Bus (+) high
Views:
UK: 21
EN: 29
RU: 28
AI status
Completed
Completed
100%
Causes
- Short to battery/ignition voltage on CAN (+) conductor
- Failed CAN transceiver in one or more control modules
- Damaged wiring harness or chafed/shorted conductor
- Poor/loose/corroded connector terminals
- Faulty termination resistor or improper termination
- Aftermarket accessories incorrectly connected to the CAN circuit
Symptoms
- MIL or network-related warning lamps illuminated
- Loss of communication with one or more body/control modules on medium-speed CAN
- Intermittent or complete failure of systems tied to that bus (e.g., HVAC, doors, keyless entry, instrument cluster messages)
- Possible increased battery drain if a module is powering the bus
- Erratic or frozen module operation for devices on the medium-speed CAN
What to check
- Read and record all U‑codes and freeze frame data with a capable scan tool
- Visually inspect CAN wiring, connectors and harness near modules and along routing for damage, pin corrosion, or shorts
- Measure DC voltage between CAN (+) and vehicle ground with ignition ON; compare to expected idle range
- Measure DC voltage between CAN (+) and CAN (−) and between CAN (−) and ground
- Check continuity and resistance of CAN bus termination (expect roughly 60 Ω across CAN+ and CAN− with key ON and no modules disconnected)
- Use a lab scope to view CAN waveform for bus idle level, dominant level and high-voltage spikes
Signal parameters
- Normal idle common-mode bus voltage: approx. 2.5 V (both lines close to this)
- Normal dominant state differential: CAN+ rises and CAN− falls to create ~2.0 V differential
- Abnormal/high condition: CAN (+) sustained above ~3.5–4.0 V suggests short to battery or stuck driver
- Expected termination resistance: ~60 Ω across CAN+ and CAN− (two 120 Ω in parallel typical)
- Use oscilloscope for: clean recessive waveform (~2.5 V), clear dominant transitions, absence of sustained DC offset or high-voltage spikes
Diagnostic algorithm
- Record trouble codes and freeze-frame data; note which modules report loss of communication.
- Visually inspect connectors and wiring along the medium-speed CAN circuit, especially near recent service areas and where harnesses flex.
- With ignition ON (engine off), measure CAN(+) to ground and CAN(−) to ground at a convenient connector. Compare to expected idle values.
- Measure resistance across CAN+ and CAN− with ignition ON; verify ~60 Ω. If open or very low, isolate cause.
- Use a lab scope to examine the CAN(+) waveform for sustained high voltage, missing recessive level, or abnormal noise/spikes.
- If CAN(+) is high, systematically isolate by disconnecting modules on that bus one at a time (start with easily accessible body modules) until the voltage returns to normal or the code clears. Note which disconnect changes the condition.
- If disconnecting a module clears the fault, suspect that module’s transceiver or its power/ground circuits; inspect and test the module and replace if necessary.
- If no module isolation locates the fault, inspect harness for a short to battery. Repair wiring or connector faults and retest.
- After repairs, clear codes and road/test to confirm the fault does not return. Re-scan to verify communication restored to all modules.
Likely causes
- Short to constant or switched 12 V at CAN (+) due to chafed wire or pin contact
- Faulty module transceiver driving CAN (+) high (common failure in modules with internal drivers)
- Connector corrosion or bent pins causing voltage feed-through
- Missing or open CAN termination causing abnormal bus biasing
- Recent repairs or aftermarket installations that tapped into CAN wiring
Fault status
Status
Medium-speed CAN (+) circuit voltage is higher than expected, causing loss/degradation of communication on the medium-speed CAN bus. Possible short to battery or a module driving the bus high.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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