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Home / DTC / U0291 — Lost Communication With Gear Shift Control Module B

U0291 — Lost Communication With Gear Shift Control Module B

Detailed page for trouble code U0291.

34,405codes
59brands
11,914generic
22,491specific
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U0291

Generic U — Network/User

Lost Communication With Gear Shift Control Module B

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

Causes

  • Open or short in CAN/LIN communication wiring
  • Faulty Gear Shift Control Module B (power, ground, internal failure)
  • Poor connector terminals or corrosion at module or junctions
  • Missing or incorrect termination resistor(s) on CAN bus
  • Low battery voltage or blown fuse supplying the module
  • Intermittent network interference or short to power/ground

Symptoms

  • Gear selector display may be blank or show incorrect gear
  • Inability to shift between certain gears or limp/limited transmission mode
  • MIL (malfunction indicator light) or transmission warning lamp illuminated
  • Loss of shift-by-wire function or delayed shift response
  • Stored communication-related OBD-II U-codes

What to check

  • Read and record all codes and freeze frame data with a capable scan tool
  • Verify module presence using scan tool (can you communicate with Gear Shift Control Module B?)
  • Inspect wiring harness and connectors for damage, corrosion, or loose pins at the module and associated junctions
  • Measure CAN bus idle voltages: CAN_H ≈ 2.5V–3.5V, CAN_L ≈ 1.5V–2.5V (approx. 2.5V common mode); check for shorts to battery or ground
  • Check resistance between CAN_H and CAN_L at two network ends — approx. 60Ω (two 120Ω terminators in parallel) for a healthy CAN bus
  • Verify module supply voltage and ground continuity, and check related fuses and relays

Signal parameters

  • CAN bus idle voltages: CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V (typical)
  • Typical bus termination: ~60 Ω measured across CAN_H and CAN_L at vehicle ignition on
  • Expected message frequency: periodic gear-shift/status messages (commonly 10–200 ms depending on vehicle)
  • Bus speeds commonly used: 250 kb/s or 500 kb/s (verify vehicle-specific)
  • No valid module ID or no periodic messages from Gear Shift Control Module B reported by scan tool

Diagnostic algorithm

  1. Retrieve freeze frame and all active/history codes. Note any other U-codes or module-specific faults.
  2. Attempt to communicate with Gear Shift Control Module B using a manufacturer-capable scan tool. Note whether the module is present and responsive.
  3. Visually inspect the module connector(s), harness, and any splice/junctions for damage, corrosion, or water ingress. Repair as needed.
  4. Verify module power and ground: with ignition ON, measure supply voltage at the module connector and check ground resistance to chassis (
  5. Check CAN bus at the module: measure CAN_H and CAN_L voltages, and resistance between them. Look for shorts to battery or ground on each line.
  6. If bus voltages or termination resistances are abnormal, isolate sections of the network by disconnecting modules or harness branches to locate the fault.
  7. Wiggle-test connectors and harness while monitoring network messages with the scan tool to reproduce intermittent faults.
  8. If wiring and power/ground are good but the module does not respond, consider swapping with a known-good module (if available) or bench-testing the module per manufacturer procedure.
  9. If module replacement is required, program/configure it as required by vehicle manufacturer. Clear codes and perform a full system test and road test.
  10. If intermittent, monitor bus and re-check codes after extended driving or diagnostic session to confirm repair.

Likely causes

  • Damaged or disconnected CAN high/low wires to Gear Shift Control Module B
  • Loss of module supply voltage or ground at the module connector
  • Failed module hardware or internal CAN transceiver
  • Corroded connector pins or poor pin contact
  • Incorrect or missing bus termination (open/shorted 120Ω resistors)

Fault status

⚠️ Status
Lost Communication With Gear Shift Control Module B — No or irregular CAN/LIN messages received from the module. May be intermittent or permanent loss of communication.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

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Code

U0291

HYUNDAI U — Network/User

Lost Communication With Gear Shift Control Module “B”

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

Causes

  • Open or short in CAN/LIN communication wiring
  • Faulty Gear Shift Control Module B (power, ground, internal failure)
  • Poor connector terminals or corrosion at module or junctions
  • Missing or incorrect termination resistor(s) on CAN bus
  • Low battery voltage or blown fuse supplying the module
  • Intermittent network interference or short to power/ground

Symptoms

  • Gear selector display may be blank or show incorrect gear
  • Inability to shift between certain gears or limp/limited transmission mode
  • MIL (malfunction indicator light) or transmission warning lamp illuminated
  • Loss of shift-by-wire function or delayed shift response
  • Stored communication-related OBD-II U-codes

What to check

  • Read and record all codes and freeze frame data with a capable scan tool
  • Verify module presence using scan tool (can you communicate with Gear Shift Control Module B?)
  • Inspect wiring harness and connectors for damage, corrosion, or loose pins at the module and associated junctions
  • Measure CAN bus idle voltages: CAN_H ≈ 2.5V–3.5V, CAN_L ≈ 1.5V–2.5V (approx. 2.5V common mode); check for shorts to battery or ground
  • Check resistance between CAN_H and CAN_L at two network ends — approx. 60Ω (two 120Ω terminators in parallel) for a healthy CAN bus
  • Verify module supply voltage and ground continuity, and check related fuses and relays

Signal parameters

  • CAN bus idle voltages: CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V (typical)
  • Typical bus termination: ~60 Ω measured across CAN_H and CAN_L at vehicle ignition on
  • Expected message frequency: periodic gear-shift/status messages (commonly 10–200 ms depending on vehicle)
  • Bus speeds commonly used: 250 kb/s or 500 kb/s (verify vehicle-specific)
  • No valid module ID or no periodic messages from Gear Shift Control Module B reported by scan tool

Diagnostic algorithm

  1. Retrieve freeze frame and all active/history codes. Note any other U-codes or module-specific faults.
  2. Attempt to communicate with Gear Shift Control Module B using a manufacturer-capable scan tool. Note whether the module is present and responsive.
  3. Visually inspect the module connector(s), harness, and any splice/junctions for damage, corrosion, or water ingress. Repair as needed.
  4. Verify module power and ground: with ignition ON, measure supply voltage at the module connector and check ground resistance to chassis (
  5. Check CAN bus at the module: measure CAN_H and CAN_L voltages, and resistance between them. Look for shorts to battery or ground on each line.
  6. If bus voltages or termination resistances are abnormal, isolate sections of the network by disconnecting modules or harness branches to locate the fault.
  7. Wiggle-test connectors and harness while monitoring network messages with the scan tool to reproduce intermittent faults.
  8. If wiring and power/ground are good but the module does not respond, consider swapping with a known-good module (if available) or bench-testing the module per manufacturer procedure.
  9. If module replacement is required, program/configure it as required by vehicle manufacturer. Clear codes and perform a full system test and road test.
  10. If intermittent, monitor bus and re-check codes after extended driving or diagnostic session to confirm repair.

Likely causes

  • Damaged or disconnected CAN high/low wires to Gear Shift Control Module B
  • Loss of module supply voltage or ground at the module connector
  • Failed module hardware or internal CAN transceiver
  • Corroded connector pins or poor pin contact
  • Incorrect or missing bus termination (open/shorted 120Ω resistors)

Fault status

⚠️ Status
Lost Communication With Gear Shift Control Module B — No or irregular CAN/LIN messages received from the module. May be intermittent or permanent loss of communication.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

U0100 U0121 U0290 U0292
371

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HYUNDAI

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Code

U0291

LAND ROVER U — Network/User

Lost communication with the gear shift module B

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

Causes

  • Open or short in CAN/LIN communication wiring
  • Faulty Gear Shift Control Module B (power, ground, internal failure)
  • Poor connector terminals or corrosion at module or junctions
  • Missing or incorrect termination resistor(s) on CAN bus
  • Low battery voltage or blown fuse supplying the module
  • Intermittent network interference or short to power/ground

Symptoms

  • Gear selector display may be blank or show incorrect gear
  • Inability to shift between certain gears or limp/limited transmission mode
  • MIL (malfunction indicator light) or transmission warning lamp illuminated
  • Loss of shift-by-wire function or delayed shift response
  • Stored communication-related OBD-II U-codes

What to check

  • Read and record all codes and freeze frame data with a capable scan tool
  • Verify module presence using scan tool (can you communicate with Gear Shift Control Module B?)
  • Inspect wiring harness and connectors for damage, corrosion, or loose pins at the module and associated junctions
  • Measure CAN bus idle voltages: CAN_H ≈ 2.5V–3.5V, CAN_L ≈ 1.5V–2.5V (approx. 2.5V common mode); check for shorts to battery or ground
  • Check resistance between CAN_H and CAN_L at two network ends — approx. 60Ω (two 120Ω terminators in parallel) for a healthy CAN bus
  • Verify module supply voltage and ground continuity, and check related fuses and relays

Signal parameters

  • CAN bus idle voltages: CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V (typical)
  • Typical bus termination: ~60 Ω measured across CAN_H and CAN_L at vehicle ignition on
  • Expected message frequency: periodic gear-shift/status messages (commonly 10–200 ms depending on vehicle)
  • Bus speeds commonly used: 250 kb/s or 500 kb/s (verify vehicle-specific)
  • No valid module ID or no periodic messages from Gear Shift Control Module B reported by scan tool

Diagnostic algorithm

  1. Retrieve freeze frame and all active/history codes. Note any other U-codes or module-specific faults.
  2. Attempt to communicate with Gear Shift Control Module B using a manufacturer-capable scan tool. Note whether the module is present and responsive.
  3. Visually inspect the module connector(s), harness, and any splice/junctions for damage, corrosion, or water ingress. Repair as needed.
  4. Verify module power and ground: with ignition ON, measure supply voltage at the module connector and check ground resistance to chassis (
  5. Check CAN bus at the module: measure CAN_H and CAN_L voltages, and resistance between them. Look for shorts to battery or ground on each line.
  6. If bus voltages or termination resistances are abnormal, isolate sections of the network by disconnecting modules or harness branches to locate the fault.
  7. Wiggle-test connectors and harness while monitoring network messages with the scan tool to reproduce intermittent faults.
  8. If wiring and power/ground are good but the module does not respond, consider swapping with a known-good module (if available) or bench-testing the module per manufacturer procedure.
  9. If module replacement is required, program/configure it as required by vehicle manufacturer. Clear codes and perform a full system test and road test.
  10. If intermittent, monitor bus and re-check codes after extended driving or diagnostic session to confirm repair.

Likely causes

  • Damaged or disconnected CAN high/low wires to Gear Shift Control Module B
  • Loss of module supply voltage or ground at the module connector
  • Failed module hardware or internal CAN transceiver
  • Corroded connector pins or poor pin contact
  • Incorrect or missing bus termination (open/shorted 120Ω resistors)

Fault status

⚠️ Status
Lost Communication With Gear Shift Control Module B — No or irregular CAN/LIN messages received from the module. May be intermittent or permanent loss of communication.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

U0100 U0121 U0290 U0292
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.
Send to email

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