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Home / DTC / U0261 — Lost Communication With Seat Control Switch Module “B”

U0261 — Lost Communication With Seat Control Switch Module “B”

Detailed page for trouble code U0261.

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Code

U0261

HYUNDAI U — Network/User

Lost Communication With Seat Control Switch Module “B”

Brand: HYUNDAI
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Blown fuse or loss of power to the seat control switch module
  • Open, shorted or corroded connector/wiring on the CAN High/Low or power/ground circuits
  • Faulty Seat Control Switch Module “B” (internal failure)
  • Poor or missing ground at the module
  • Failed termination resistor or shorted CAN bus
  • Other module on the same CAN bus driving the line low/high or creating a bus fault

Symptoms

  • Seat adjustment switches unresponsive or intermittent
  • Seat memory, seat heating or ventilation functions not available for that seat
  • Driver information display or message indicating seat module communication fault
  • Multiple related DTCs or reduced functionality in other modules that use seat status
  • Possible fuse blown or other electrical accessory failures

What to check

  • Read all stored DTCs and freeze frame data with a scan tool; note related U-codes and modules absent from network
  • Check battery voltage (key on) and attempt communications with other modules to confirm overall CAN functionality
  • Inspect fuses for seat/comfort modules and replace if blown; verify circuit power at the module connector with a multimeter
  • Visually inspect seat harness, connectors and under-seat area for damage, corrosion, water intrusion or pinched wires
  • Using a scan tool, attempt to communicate directly with Seat Control Switch Module B; note if module is present on the network
  • Measure CAN bus voltages at the module connector: CAN_H and CAN_L with key ON and while operating seat switches; check against expected idle/dominant levels

Signal parameters

  • Typical HS-CAN baud rate: 500 kbps (verify for the specific model/year)
  • Idle voltages (no dominant): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each to chassis)
  • Dominant bit state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (approx. 2.0 V differential)
  • Termination resistance across CAN_H/CAN_L ≈ 60 ohms (two 120 Ω terminators in parallel)
  • Module supply: +12 V battery (key ON) to module Vbat pin; ground reference at module chassis ground

Diagnostic algorithm

  1. Verify complaint and read all DTCs: record U0261 and any other network-related codes.
  2. Check battery voltage and health. Low voltage or weak battery can cause communication faults.
  3. Inspect fuses related to seat/comfort modules and replace if blown. If fuse blows again, suspect short to power.
  4. Visually inspect seat wiring and connectors (especially under the seat). Repair any damaged wiring or connectors.
  5. With a scan tool, attempt to communicate with the Seat Control Switch Module B. If module not present, continue network checks.
  6. Check power and ground at the module connector: verify constant battery (or ignition-switched) voltage and a good ground. Repair as needed.
  7. Measure CAN_H and CAN_L at the module connector with a scope or multimeter: verify idle voltages and that the differential shifts during bus activity. If voltages abnormal, isolate wiring or a shorted node.
  8. Measure resistance between CAN_H and CAN_L with ignition off — expect ≈60 Ω. If infinite or very low, locate open or short (respectively).
  9. If an individual module is shorting the bus, disconnect the seat module and see if the bus returns to normal and other modules communicate. If disconnecting the seat module clears the fault, replace or repair the seat control switch module.
  10. If wiring and module power/ground are good but no communication, replace the Seat Control Switch Module B. After replacement, program/configure the new module per manufacturer procedure.
  11. Clear codes and retest all seat functions and network communications. Verify no reoccurrence and that related modules regain normal status.

Likely causes

  • Intermittent or open power/ground to the seat control switch module
  • Damaged CAN-H / CAN-L wiring or connector corrosion at seat harness or under-seat area
  • Failed seat control switch module
  • Aftermarket device or recent body repair disturbed the CAN network or connectors
  • Faulty termination resistor or short to battery/ground on CAN lines

Fault status

⚠️ Status
Lost Communication With Seat Control Switch Module "B" — No response from module on CAN bus
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0260 U0100 U0155 U0121
371

Browse 371 HYUNDAI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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