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Home / DTC / U0209 — Lost Communication With Seat Control Module B

U0209 — Lost Communication With Seat Control Module B

Detailed page for trouble code U0209.

34,405codes
59brands
11,914generic
22,491specific
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U0209

Generic U — Network/User

Lost Communication With Seat Control Module B

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

Causes

  • Faulty or disconnected seat control module (module B)
  • Damaged wiring or connector between module and network
  • Blown fuse or loss of module power/ground
  • Faulty CAN or LIN bus (open, short, high resistance, missing termination)
  • Intermittent connection (corrosion, bent pins, water intrusion)
  • Another module interfering on the network or bus contention

Symptoms

  • Seat functions inoperative or intermittent (adjustment, memory, heating/ventilation, lumbar)
  • Related modules report seat-related faults or reduced features
  • Stored U0209 and possibly other communication codes
  • Possible illumination of generic warning lamp or message on dash
  • Seat position not saved or recalled

What to check

  • Use a scan tool to confirm U0209, note freeze-frame and any simultaneous communication codes
  • Check for additional related DTCs (other U01xx/U02xx or module-specific codes)
  • Visually inspect seat module connector for corrosion, bent pins, water, or damage
  • Verify fuses and relays supplying the seat control module
  • Backprobe and measure key power and ground circuits at the module
  • Check CAN/LIN bus voltages at the seat module connector with key on

Signal parameters

  • CAN bus recessive voltage: each line typically near 2.5 V (both lines equal)
  • CAN dominant state: CAN_H ~3.5 V and CAN_L ~1.5 V (differential ~1.5–2.0 V)
  • CAN termination resistance: ~60 ohms across CAN_H and CAN_L (two 120 Ω in parallel)
  • LIN bus idle: typically pulled high to battery voltage via resistor (varies by manufacturer)
  • Expected: seat control module should appear on network and respond to periodic messages/ID; absence indicates lost communication

Diagnostic algorithm

  1. Connect an OEM-capable scan tool. Record U0209 and any other network codes, note freeze-frame data and timestamps.
  2. Attempt to communicate with Seat Control Module B via scan tool. If no response, attempt a module present/ID request if allowed.
  3. Visually inspect module connector and harness for corrosion, damage, or water intrusion. Repair as needed.
  4. Verify fuse(s) and measure battery voltage at the module's power pin with ignition on. Confirm a good ground at module ground pin.
  5. With ignition on, measure CAN_H and CAN_L voltages at the module connector. Compare to expected values. If voltages abnormal, isolate wiring to nearest junction or gateway.
  6. Check continuity and shorts: measure resistance between CAN_H and CAN_L (terminals disconnected) and check for shorts to battery and ground.
  7. Inspect/measure termination resistors near gateway/BCM. Replace or repair if termination missing or incorrect.
  8. If wiring and power/ground are good but no communication, try swapping with a known good seat module (if available) or substitute known-good gateway/BCM only when guided by OEM procedures.
  9. Reprogram or reflash module software per OEM instructions if module responds but shows software faults.
  10. Clear codes and perform function test. Monitor for reoccurrence and verify related seat functions operate normally.

Likely causes

  • Corroded/loose connector at the seat control module
  • Power or ground missing at the seat control module
  • Open or shorted CAN/LIN wiring between module and central gateway/BCM
  • Failed seat control module
  • Missing or incorrect bus termination or short to battery/ground on bus

Fault status

⚠️ Status
Lost Communication With Seat Control Module B — the seat control module is not responding on the vehicle network (CAN/LIN).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

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Code

U0209

HYUNDAI U — Network/User

Lost Communication With “Seat Control Module B”

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

Causes

  • Faulty or disconnected seat control module (module B)
  • Damaged wiring or connector between module and network
  • Blown fuse or loss of module power/ground
  • Faulty CAN or LIN bus (open, short, high resistance, missing termination)
  • Intermittent connection (corrosion, bent pins, water intrusion)
  • Another module interfering on the network or bus contention

Symptoms

  • Seat functions inoperative or intermittent (adjustment, memory, heating/ventilation, lumbar)
  • Related modules report seat-related faults or reduced features
  • Stored U0209 and possibly other communication codes
  • Possible illumination of generic warning lamp or message on dash
  • Seat position not saved or recalled

What to check

  • Use a scan tool to confirm U0209, note freeze-frame and any simultaneous communication codes
  • Check for additional related DTCs (other U01xx/U02xx or module-specific codes)
  • Visually inspect seat module connector for corrosion, bent pins, water, or damage
  • Verify fuses and relays supplying the seat control module
  • Backprobe and measure key power and ground circuits at the module
  • Check CAN/LIN bus voltages at the seat module connector with key on

Signal parameters

  • CAN bus recessive voltage: each line typically near 2.5 V (both lines equal)
  • CAN dominant state: CAN_H ~3.5 V and CAN_L ~1.5 V (differential ~1.5–2.0 V)
  • CAN termination resistance: ~60 ohms across CAN_H and CAN_L (two 120 Ω in parallel)
  • LIN bus idle: typically pulled high to battery voltage via resistor (varies by manufacturer)
  • Expected: seat control module should appear on network and respond to periodic messages/ID; absence indicates lost communication

Diagnostic algorithm

  1. Connect an OEM-capable scan tool. Record U0209 and any other network codes, note freeze-frame data and timestamps.
  2. Attempt to communicate with Seat Control Module B via scan tool. If no response, attempt a module present/ID request if allowed.
  3. Visually inspect module connector and harness for corrosion, damage, or water intrusion. Repair as needed.
  4. Verify fuse(s) and measure battery voltage at the module's power pin with ignition on. Confirm a good ground at module ground pin.
  5. With ignition on, measure CAN_H and CAN_L voltages at the module connector. Compare to expected values. If voltages abnormal, isolate wiring to nearest junction or gateway.
  6. Check continuity and shorts: measure resistance between CAN_H and CAN_L (terminals disconnected) and check for shorts to battery and ground.
  7. Inspect/measure termination resistors near gateway/BCM. Replace or repair if termination missing or incorrect.
  8. If wiring and power/ground are good but no communication, try swapping with a known good seat module (if available) or substitute known-good gateway/BCM only when guided by OEM procedures.
  9. Reprogram or reflash module software per OEM instructions if module responds but shows software faults.
  10. Clear codes and perform function test. Monitor for reoccurrence and verify related seat functions operate normally.

Likely causes

  • Corroded/loose connector at the seat control module
  • Power or ground missing at the seat control module
  • Open or shorted CAN/LIN wiring between module and central gateway/BCM
  • Failed seat control module
  • Missing or incorrect bus termination or short to battery/ground on bus

Fault status

⚠️ Status
Lost Communication With Seat Control Module B — the seat control module is not responding on the vehicle network (CAN/LIN).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0121 U0122 U0142 U0155
371

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

HYUNDAI

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Code

U0209

LAND ROVER U — Network/User

Lost communication with seat control module B

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

Causes

  • Faulty or disconnected seat control module (module B)
  • Damaged wiring or connector between module and network
  • Blown fuse or loss of module power/ground
  • Faulty CAN or LIN bus (open, short, high resistance, missing termination)
  • Intermittent connection (corrosion, bent pins, water intrusion)
  • Another module interfering on the network or bus contention

Symptoms

  • Seat functions inoperative or intermittent (adjustment, memory, heating/ventilation, lumbar)
  • Related modules report seat-related faults or reduced features
  • Stored U0209 and possibly other communication codes
  • Possible illumination of generic warning lamp or message on dash
  • Seat position not saved or recalled

What to check

  • Use a scan tool to confirm U0209, note freeze-frame and any simultaneous communication codes
  • Check for additional related DTCs (other U01xx/U02xx or module-specific codes)
  • Visually inspect seat module connector for corrosion, bent pins, water, or damage
  • Verify fuses and relays supplying the seat control module
  • Backprobe and measure key power and ground circuits at the module
  • Check CAN/LIN bus voltages at the seat module connector with key on

Signal parameters

  • CAN bus recessive voltage: each line typically near 2.5 V (both lines equal)
  • CAN dominant state: CAN_H ~3.5 V and CAN_L ~1.5 V (differential ~1.5–2.0 V)
  • CAN termination resistance: ~60 ohms across CAN_H and CAN_L (two 120 Ω in parallel)
  • LIN bus idle: typically pulled high to battery voltage via resistor (varies by manufacturer)
  • Expected: seat control module should appear on network and respond to periodic messages/ID; absence indicates lost communication

Diagnostic algorithm

  1. Connect an OEM-capable scan tool. Record U0209 and any other network codes, note freeze-frame data and timestamps.
  2. Attempt to communicate with Seat Control Module B via scan tool. If no response, attempt a module present/ID request if allowed.
  3. Visually inspect module connector and harness for corrosion, damage, or water intrusion. Repair as needed.
  4. Verify fuse(s) and measure battery voltage at the module's power pin with ignition on. Confirm a good ground at module ground pin.
  5. With ignition on, measure CAN_H and CAN_L voltages at the module connector. Compare to expected values. If voltages abnormal, isolate wiring to nearest junction or gateway.
  6. Check continuity and shorts: measure resistance between CAN_H and CAN_L (terminals disconnected) and check for shorts to battery and ground.
  7. Inspect/measure termination resistors near gateway/BCM. Replace or repair if termination missing or incorrect.
  8. If wiring and power/ground are good but no communication, try swapping with a known good seat module (if available) or substitute known-good gateway/BCM only when guided by OEM procedures.
  9. Reprogram or reflash module software per OEM instructions if module responds but shows software faults.
  10. Clear codes and perform function test. Monitor for reoccurrence and verify related seat functions operate normally.

Likely causes

  • Corroded/loose connector at the seat control module
  • Power or ground missing at the seat control module
  • Open or shorted CAN/LIN wiring between module and central gateway/BCM
  • Failed seat control module
  • Missing or incorrect bus termination or short to battery/ground on bus

Fault status

⚠️ Status
Lost Communication With Seat Control Module B — the seat control module is not responding on the vehicle network (CAN/LIN).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0121 U0122 U0142 U0155
320

Browse 320 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

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+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
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