Code
U0261
Generic
U — Network/User
Lost Communication With Seat Control Switch Module B
AI status
Completed
Completed
100%
Causes
- Open or short in network wiring (CAN/LIN) to the seat control switch module
- Poor or corroded connector or pin at the seat control switch module
- Blown fuse or loss of module power or ground
- Seat control switch module internal failure
- Network termination or wiring fault causing bus off or excessive errors
- Intermittent connection due to seat movement (pinch points) or rubbing wires
Symptoms
- Seat adjustment switches do not operate or are intermittent
- Seat memory, lumbar, heating, or other seat features inoperative
- Warning message or DTC indicator related to seat system or communication
- Multiple modules report communication or network-related DTCs
- No module data available for Seat Control Switch Module B in the scan tool
What to check
- Retrieve all stored and pending network codes and note freeze frame if available
- Check for other U‑codes indicating broader network issues (bus off, other module comms)
- Confirm module presence with a diagnostic scanner (can you communicate or request data?)
- Inspect fuses and power/ground at the seat control switch module connector
- Visually inspect connectors and harness for damage, corrosion, or pin pushed out
- Measure CAN or LIN bus voltages at the module connector with key on, engine off
Signal parameters
- CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive); dominant levels typically CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V
- Differential CAN amplitude when active ≈ 2.0 V
- Typical bus termination equivalent ≈ 60 ohms across CAN_H and CAN_L (two 120 Ω resistors in parallel)
- Module supply voltage: battery voltage present at module power pin with ignition on
- Ground continuity: near 0 Ω from module ground pin to chassis ground
- Message presence: module-specific CAN frames or IDs not present or intermittent when present
Diagnostic algorithm
- Confirm the U0261 code and record any other network DTCs. Clear codes and see if U0261 returns.
- Using a scan tool, attempt to communicate with Seat Control Switch Module B. Note if module appears on the network or is absent.
- Inspect fuses and verify battery voltage at the module's power pin and good ground at module ground pin.
- Visually inspect the module connector and harness for damage, corrosion, bent pins, or loose terminals. Repair as needed.
- Check CAN/LIN bus voltages at the module connector with key on. Verify idle and dominant voltages and check for proper termination resistance.
- If bus voltages are abnormal, isolate the short/open by disconnecting segments (unplug modules or harness branches) while monitoring bus behavior to locate the fault.
- Perform a wiggle test and move seat through full travel while monitoring the network for intermittent communication restoration/loss.
- If harness and power/ground are good but the module does not respond, verify software/calibration compatibility if module was recently replaced or updated.
- If available, swap with a known-good seat switch module or bench-test the module to confirm failure before replacement.
- After repair or replacement, clear codes and verify full functionality and that no related network DTCs remain.
Likely causes
- Loose/corroded connector or damaged wiring in harness to seat switch module
- Module not powered (blown fuse, missing battery feed, or bad ground)
- CAN/LIN bus fault (open, short to battery/ground, or missing termination)
- Seat control switch module failure
Fault status
Status
Lost Communication With Seat Control Switch Module B — module not responding on vehicle network
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Repair manuals
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Code
U0261
HYUNDAI
U — Network/User
Lost Communication With Seat Control Switch Module “B”
AI status
Completed
Completed
100%
Causes
- Open or short in network wiring (CAN/LIN) to the seat control switch module
- Poor or corroded connector or pin at the seat control switch module
- Blown fuse or loss of module power or ground
- Seat control switch module internal failure
- Network termination or wiring fault causing bus off or excessive errors
- Intermittent connection due to seat movement (pinch points) or rubbing wires
Symptoms
- Seat adjustment switches do not operate or are intermittent
- Seat memory, lumbar, heating, or other seat features inoperative
- Warning message or DTC indicator related to seat system or communication
- Multiple modules report communication or network-related DTCs
- No module data available for Seat Control Switch Module B in the scan tool
What to check
- Retrieve all stored and pending network codes and note freeze frame if available
- Check for other U‑codes indicating broader network issues (bus off, other module comms)
- Confirm module presence with a diagnostic scanner (can you communicate or request data?)
- Inspect fuses and power/ground at the seat control switch module connector
- Visually inspect connectors and harness for damage, corrosion, or pin pushed out
- Measure CAN or LIN bus voltages at the module connector with key on, engine off
Signal parameters
- CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive); dominant levels typically CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V
- Differential CAN amplitude when active ≈ 2.0 V
- Typical bus termination equivalent ≈ 60 ohms across CAN_H and CAN_L (two 120 Ω resistors in parallel)
- Module supply voltage: battery voltage present at module power pin with ignition on
- Ground continuity: near 0 Ω from module ground pin to chassis ground
- Message presence: module-specific CAN frames or IDs not present or intermittent when present
Diagnostic algorithm
- Confirm the U0261 code and record any other network DTCs. Clear codes and see if U0261 returns.
- Using a scan tool, attempt to communicate with Seat Control Switch Module B. Note if module appears on the network or is absent.
- Inspect fuses and verify battery voltage at the module's power pin and good ground at module ground pin.
- Visually inspect the module connector and harness for damage, corrosion, bent pins, or loose terminals. Repair as needed.
- Check CAN/LIN bus voltages at the module connector with key on. Verify idle and dominant voltages and check for proper termination resistance.
- If bus voltages are abnormal, isolate the short/open by disconnecting segments (unplug modules or harness branches) while monitoring bus behavior to locate the fault.
- Perform a wiggle test and move seat through full travel while monitoring the network for intermittent communication restoration/loss.
- If harness and power/ground are good but the module does not respond, verify software/calibration compatibility if module was recently replaced or updated.
- If available, swap with a known-good seat switch module or bench-test the module to confirm failure before replacement.
- After repair or replacement, clear codes and verify full functionality and that no related network DTCs remain.
Likely causes
- Loose/corroded connector or damaged wiring in harness to seat switch module
- Module not powered (blown fuse, missing battery feed, or bad ground)
- CAN/LIN bus fault (open, short to battery/ground, or missing termination)
- Seat control switch module failure
Fault status
Status
Lost Communication With Seat Control Switch Module B — module not responding on vehicle network
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Repair manuals
Manual library for HYUNDAI
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