Code
U2104
HUMMER
U — Network/User
CAN Bus Reset Counter Overrun
Views:
UK: 11
EN: 25
RU: 18
AI status
Completed
Completed
100%
Causes
- Intermittent CAN bus wiring (open/short/poor contact)
- Bad or loose connector at one or more modules
- Faulty module repeatedly resetting (internal fault or power glitch)
- Low or unstable battery/ignition supply to networked modules
- Missing or incorrect bus termination (resistors) or improper network topology
- High electrical noise or excessive bus load (aftermarket device, shorted node)
Symptoms
- Manufacturer-specific warning or communication fault messages on dash
- Loss or intermittent loss of specific vehicle functions (e.g., instrument cluster, doors, HVAC)
- Multiple communication-related U-codes stored in one or more modules
- Modules reporting repeated power cycles or reset events in freeze frame/logs
- No drivability symptoms may be present if only non-powertrain networks are affected
What to check
- Read all module memory with a factory-level scan tool; record U2104, related U-codes and freeze frame data
- Identify which module logged U2104 and check that module’s power and ground circuits
- Inspect CAN High/Low wiring, connectors, and pin condition at affected modules and gateway
- Check battery voltage and charging system; test for voltage drops during key cycles and crashes
- Verify CAN termination (approx. 60 ohm across CAN H/L at rest or two 120 ohm resistors at ends)
- Use scope or scan-tool bus diagnostics to view CAN waveforms, error frames, bus load and bit timing
Signal parameters
- CAN High/Low voltage idle (~2.5 V common-mode; differential ±1.5 V typical)
- Differential amplitude of CAN frames (~2.5 V High − Low ≈ 2 V)
- Bus idle resistance across CAN H/L ~60 ohms (two 120 ohm terminators in parallel)
- Number of CAN error frames per minute/session
- Reset counter value logged by module and timestamp of resets
- Bus load percentage or message rate (messages/sec)
Diagnostic algorithm
- Use a factory-capable scan tool to identify which module set U2104 and note time stamps and freeze frame data.
- Check battery state-of-charge and charging system; ensure stable supply (measure at rest and while cranking).
- Visually inspect and repair any corroded/damaged connectors and wiring on CAN H/L and module power/ground. Wiggle wiring while monitoring bus for errors.
- With key on, use a lab scope or CAN bus analyzer to look for proper differential waveforms, excessive error frames or dominant states. Record anomalies.
- Measure termination resistance across CAN H/L. Remove connectors as needed to isolate segments and re-check. Repair missing/incorrect termination.
- Isolate modules by disconnecting non-critical modules or aftermarket devices one at a time while monitoring reset counter and error frame rate to find offending node.
- If a specific module is rebooting, verify its power and ground circuits at the module connector and replace or repair as required. Consider reflashing module software if corrupted.
- After repairs, clear codes, cycle key and road-test; monitor for reappearance of U2104 and related communication DTCs.
- If intermittent and unresolved, consult manufacturer technical service bulletins or perform extended data logging with a CAN analyzer for pattern identification.
Likely causes
- Intermittent wiring/connector fault on CAN High/Low to a module
- One module losing power or rebooting repeatedly (bad ECU or internal power regulator)
- Corroded or loose battery/ground connection causing brownouts
- Aftermarket accessory placed on the CAN network causing errors
Fault status
Status
CAN Bus Reset Counter Overrun — repeated network resets detected; communication may be impaired.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
U2104
LAND ROVER
U — Network/User
Meter reset button shot
Views:
UK: 6
EN: 9
RU: 10
AI status
Completed
Completed
100%
Causes
- Intermittent CAN bus wiring (open/short/poor contact)
- Bad or loose connector at one or more modules
- Faulty module repeatedly resetting (internal fault or power glitch)
- Low or unstable battery/ignition supply to networked modules
- Missing or incorrect bus termination (resistors) or improper network topology
- High electrical noise or excessive bus load (aftermarket device, shorted node)
Symptoms
- Manufacturer-specific warning or communication fault messages on dash
- Loss or intermittent loss of specific vehicle functions (e.g., instrument cluster, doors, HVAC)
- Multiple communication-related U-codes stored in one or more modules
- Modules reporting repeated power cycles or reset events in freeze frame/logs
- No drivability symptoms may be present if only non-powertrain networks are affected
What to check
- Read all module memory with a factory-level scan tool; record U2104, related U-codes and freeze frame data
- Identify which module logged U2104 and check that module’s power and ground circuits
- Inspect CAN High/Low wiring, connectors, and pin condition at affected modules and gateway
- Check battery voltage and charging system; test for voltage drops during key cycles and crashes
- Verify CAN termination (approx. 60 ohm across CAN H/L at rest or two 120 ohm resistors at ends)
- Use scope or scan-tool bus diagnostics to view CAN waveforms, error frames, bus load and bit timing
Signal parameters
- CAN High/Low voltage idle (~2.5 V common-mode; differential ±1.5 V typical)
- Differential amplitude of CAN frames (~2.5 V High − Low ≈ 2 V)
- Bus idle resistance across CAN H/L ~60 ohms (two 120 ohm terminators in parallel)
- Number of CAN error frames per minute/session
- Reset counter value logged by module and timestamp of resets
- Bus load percentage or message rate (messages/sec)
Diagnostic algorithm
- Use a factory-capable scan tool to identify which module set U2104 and note time stamps and freeze frame data.
- Check battery state-of-charge and charging system; ensure stable supply (measure at rest and while cranking).
- Visually inspect and repair any corroded/damaged connectors and wiring on CAN H/L and module power/ground. Wiggle wiring while monitoring bus for errors.
- With key on, use a lab scope or CAN bus analyzer to look for proper differential waveforms, excessive error frames or dominant states. Record anomalies.
- Measure termination resistance across CAN H/L. Remove connectors as needed to isolate segments and re-check. Repair missing/incorrect termination.
- Isolate modules by disconnecting non-critical modules or aftermarket devices one at a time while monitoring reset counter and error frame rate to find offending node.
- If a specific module is rebooting, verify its power and ground circuits at the module connector and replace or repair as required. Consider reflashing module software if corrupted.
- After repairs, clear codes, cycle key and road-test; monitor for reappearance of U2104 and related communication DTCs.
- If intermittent and unresolved, consult manufacturer technical service bulletins or perform extended data logging with a CAN analyzer for pattern identification.
Likely causes
- Intermittent wiring/connector fault on CAN High/Low to a module
- One module losing power or rebooting repeatedly (bad ECU or internal power regulator)
- Corroded or loose battery/ground connection causing brownouts
- Aftermarket accessory placed on the CAN network causing errors
Fault status
Status
CAN Bus Reset Counter Overrun — repeated network resets detected; communication may be impaired.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
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0
Send to email
Code
U2104
OPEL
U — Network/User
CAN-Bus reset counter overrun
Views:
UK: 2
EN: 7
RU: 6
AI status
Completed
Completed
100%
Causes
- Intermittent CAN bus wiring (open/short/poor contact)
- Bad or loose connector at one or more modules
- Faulty module repeatedly resetting (internal fault or power glitch)
- Low or unstable battery/ignition supply to networked modules
- Missing or incorrect bus termination (resistors) or improper network topology
- High electrical noise or excessive bus load (aftermarket device, shorted node)
Symptoms
- Manufacturer-specific warning or communication fault messages on dash
- Loss or intermittent loss of specific vehicle functions (e.g., instrument cluster, doors, HVAC)
- Multiple communication-related U-codes stored in one or more modules
- Modules reporting repeated power cycles or reset events in freeze frame/logs
- No drivability symptoms may be present if only non-powertrain networks are affected
What to check
- Read all module memory with a factory-level scan tool; record U2104, related U-codes and freeze frame data
- Identify which module logged U2104 and check that module’s power and ground circuits
- Inspect CAN High/Low wiring, connectors, and pin condition at affected modules and gateway
- Check battery voltage and charging system; test for voltage drops during key cycles and crashes
- Verify CAN termination (approx. 60 ohm across CAN H/L at rest or two 120 ohm resistors at ends)
- Use scope or scan-tool bus diagnostics to view CAN waveforms, error frames, bus load and bit timing
Signal parameters
- CAN High/Low voltage idle (~2.5 V common-mode; differential ±1.5 V typical)
- Differential amplitude of CAN frames (~2.5 V High − Low ≈ 2 V)
- Bus idle resistance across CAN H/L ~60 ohms (two 120 ohm terminators in parallel)
- Number of CAN error frames per minute/session
- Reset counter value logged by module and timestamp of resets
- Bus load percentage or message rate (messages/sec)
Diagnostic algorithm
- Use a factory-capable scan tool to identify which module set U2104 and note time stamps and freeze frame data.
- Check battery state-of-charge and charging system; ensure stable supply (measure at rest and while cranking).
- Visually inspect and repair any corroded/damaged connectors and wiring on CAN H/L and module power/ground. Wiggle wiring while monitoring bus for errors.
- With key on, use a lab scope or CAN bus analyzer to look for proper differential waveforms, excessive error frames or dominant states. Record anomalies.
- Measure termination resistance across CAN H/L. Remove connectors as needed to isolate segments and re-check. Repair missing/incorrect termination.
- Isolate modules by disconnecting non-critical modules or aftermarket devices one at a time while monitoring reset counter and error frame rate to find offending node.
- If a specific module is rebooting, verify its power and ground circuits at the module connector and replace or repair as required. Consider reflashing module software if corrupted.
- After repairs, clear codes, cycle key and road-test; monitor for reappearance of U2104 and related communication DTCs.
- If intermittent and unresolved, consult manufacturer technical service bulletins or perform extended data logging with a CAN analyzer for pattern identification.
Likely causes
- Intermittent wiring/connector fault on CAN High/Low to a module
- One module losing power or rebooting repeatedly (bad ECU or internal power regulator)
- Corroded or loose battery/ground connection causing brownouts
- Aftermarket accessory placed on the CAN network causing errors
Fault status
Status
CAN Bus Reset Counter Overrun — repeated network resets detected; communication may be impaired.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email