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Home / DTC / U0103 — Lost Communication With Gear Shift Control Module A

U0103 — Lost Communication With Gear Shift Control Module A

Detailed page for trouble code U0103.

34,177codes
59brands
11,686generic
22,491specific
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U0103

Generic U — Network/User

Lost Communication With Gear Shift Control Module A

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

Causes

  • Open or shorted wiring on the vehicle communication bus (CAN/LIN) to the gear shift control module
  • Faulty gear shift control module (internal failure)
  • Missing or intermittent power or ground to the module
  • Corroded, loose or damaged connectors at the module or junctions
  • Blown fuse or failed relay supplying the module
  • Network termination or grounding problem (improper CAN termination, short to battery or ground)

Symptoms

  • Transmission/gear selector not responding or unable to change gears
  • MIL/Check Engine lamp or transmission warning lamp illuminated
  • Transmission may enter limp/backup mode (reduced shifting or fixed gear)
  • Transmission shift indicator/instrument cluster may show no data or erratic readouts
  • Other modules report multiple U-codes or loss of module data
  • No communication with the gear shift control module shown on a scan tool

What to check

  • Use a scan tool to attempt communication with the Gear Shift Control Module and read freeze frame and stored codes
  • Check for other U-codes that point to a wider bus failure (multiple modules non-communicative)
  • Visually inspect module connectors and harness for corrosion, damage, or water intrusion
  • Verify battery voltage and charging system condition (stable ~12–14.5 V with key on and engine running)
  • Verify fuses and relays for the gear shift control module power circuit
  • Measure power and ground at the module connector with a DVOM

Signal parameters

  • CAN bus idle voltages: CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V (both ~2.5 V when recessive)
  • Dominant (active) CAN differential typically ~1.5–3.5 V between CAN_H and CAN_L
  • Typical CAN bus termination resistance ~60 ohms measured across CAN_H and CAN_L (two 120Ω terminators in parallel)
  • Module supply voltage ~12 V (key ON), ground continuity near 0 ohms to chassis
  • Scan tool should show module responding with periodic messages/ECU ID when communication is healthy

Diagnostic algorithm

  1. Connect a diagnostic scanner and verify U0103 is current or stored; capture freeze frame and related U-codes.
  2. Attempt to communicate directly with the Gear Shift Control Module; note if the module is completely non-responsive or intermittently visible.
  3. Inspect for obvious damage at the module harness and connectors (bent pins, corrosion, moisture). Repair as needed.
  4. Verify battery voltage and inspect/replace any blown fuses or faulty relays that supply the module.
  5. Backprobe the module power and ground pins to confirm proper supply voltage and a good ground with key ON. Repair power/ground faults before proceeding.
  6. With ignition ON, measure CAN_H and CAN_L at the module connector. Compare to expected idle voltages and check for a short to battery or ground.
  7. Measure termination resistance across CAN_H and CAN_L at two locations; compare to expected ~60 ohms. Unplugging a connector may help isolate which segment has the fault.
  8. Wiggle harnesses and connectors while monitoring communication to reproduce intermittent failures; repair wiring or connector faults found.
  9. If wiring and power/ground are good and the bus appears healthy, consider updating module software or replacing the gear shift control module per manufacturer procedures. Program/configure replacement module as required.
  10. After repairs, clear codes and road-test to confirm the fault does not return. Re-scan to ensure other modules regained communication.

Likely causes

  • Damaged or disconnected CAN high/low wires to the gear shift control module
  • Faulty connector pins (bent, corroded or pushed out) at the module harness
  • Module lost power or ground (fuse or wiring fault)
  • Module internal failure (hardware/software) after a recent event (water intrusion, impact, or electrical surge)
  • Network termination resistance out of specification causing bus communications to fail

Fault status

⚠️ Status
Lost Communication With Gear Shift Control Module A — module not responding on vehicle communication network
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

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Code

U0103

HYUNDAI U — Network/User

Lost Communication With Gear Shift Module | Lost Communication With Gear Shift Control Module “A”

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

Causes

  • Open or shorted wiring on the vehicle communication bus (CAN/LIN) to the gear shift control module
  • Faulty gear shift control module (internal failure)
  • Missing or intermittent power or ground to the module
  • Corroded, loose or damaged connectors at the module or junctions
  • Blown fuse or failed relay supplying the module
  • Network termination or grounding problem (improper CAN termination, short to battery or ground)

Symptoms

  • Transmission/gear selector not responding or unable to change gears
  • MIL/Check Engine lamp or transmission warning lamp illuminated
  • Transmission may enter limp/backup mode (reduced shifting or fixed gear)
  • Transmission shift indicator/instrument cluster may show no data or erratic readouts
  • Other modules report multiple U-codes or loss of module data
  • No communication with the gear shift control module shown on a scan tool

What to check

  • Use a scan tool to attempt communication with the Gear Shift Control Module and read freeze frame and stored codes
  • Check for other U-codes that point to a wider bus failure (multiple modules non-communicative)
  • Visually inspect module connectors and harness for corrosion, damage, or water intrusion
  • Verify battery voltage and charging system condition (stable ~12–14.5 V with key on and engine running)
  • Verify fuses and relays for the gear shift control module power circuit
  • Measure power and ground at the module connector with a DVOM

Signal parameters

  • CAN bus idle voltages: CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V (both ~2.5 V when recessive)
  • Dominant (active) CAN differential typically ~1.5–3.5 V between CAN_H and CAN_L
  • Typical CAN bus termination resistance ~60 ohms measured across CAN_H and CAN_L (two 120Ω terminators in parallel)
  • Module supply voltage ~12 V (key ON), ground continuity near 0 ohms to chassis
  • Scan tool should show module responding with periodic messages/ECU ID when communication is healthy

Diagnostic algorithm

  1. Connect a diagnostic scanner and verify U0103 is current or stored; capture freeze frame and related U-codes.
  2. Attempt to communicate directly with the Gear Shift Control Module; note if the module is completely non-responsive or intermittently visible.
  3. Inspect for obvious damage at the module harness and connectors (bent pins, corrosion, moisture). Repair as needed.
  4. Verify battery voltage and inspect/replace any blown fuses or faulty relays that supply the module.
  5. Backprobe the module power and ground pins to confirm proper supply voltage and a good ground with key ON. Repair power/ground faults before proceeding.
  6. With ignition ON, measure CAN_H and CAN_L at the module connector. Compare to expected idle voltages and check for a short to battery or ground.
  7. Measure termination resistance across CAN_H and CAN_L at two locations; compare to expected ~60 ohms. Unplugging a connector may help isolate which segment has the fault.
  8. Wiggle harnesses and connectors while monitoring communication to reproduce intermittent failures; repair wiring or connector faults found.
  9. If wiring and power/ground are good and the bus appears healthy, consider updating module software or replacing the gear shift control module per manufacturer procedures. Program/configure replacement module as required.
  10. After repairs, clear codes and road-test to confirm the fault does not return. Re-scan to ensure other modules regained communication.

Likely causes

  • Damaged or disconnected CAN high/low wires to the gear shift control module
  • Faulty connector pins (bent, corroded or pushed out) at the module harness
  • Module lost power or ground (fuse or wiring fault)
  • Module internal failure (hardware/software) after a recent event (water intrusion, impact, or electrical surge)
  • Network termination resistance out of specification causing bus communications to fail

Fault status

⚠️ Status
Lost Communication With Gear Shift Control Module A — module not responding on vehicle communication network
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0101 U0121 U0122 U0146 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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+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
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Code

U0103

LAND ROVER U — Network/User

Lost communication with the gear shift module

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

Causes

  • Open or shorted wiring on the vehicle communication bus (CAN/LIN) to the gear shift control module
  • Faulty gear shift control module (internal failure)
  • Missing or intermittent power or ground to the module
  • Corroded, loose or damaged connectors at the module or junctions
  • Blown fuse or failed relay supplying the module
  • Network termination or grounding problem (improper CAN termination, short to battery or ground)

Symptoms

  • Transmission/gear selector not responding or unable to change gears
  • MIL/Check Engine lamp or transmission warning lamp illuminated
  • Transmission may enter limp/backup mode (reduced shifting or fixed gear)
  • Transmission shift indicator/instrument cluster may show no data or erratic readouts
  • Other modules report multiple U-codes or loss of module data
  • No communication with the gear shift control module shown on a scan tool

What to check

  • Use a scan tool to attempt communication with the Gear Shift Control Module and read freeze frame and stored codes
  • Check for other U-codes that point to a wider bus failure (multiple modules non-communicative)
  • Visually inspect module connectors and harness for corrosion, damage, or water intrusion
  • Verify battery voltage and charging system condition (stable ~12–14.5 V with key on and engine running)
  • Verify fuses and relays for the gear shift control module power circuit
  • Measure power and ground at the module connector with a DVOM

Signal parameters

  • CAN bus idle voltages: CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V (both ~2.5 V when recessive)
  • Dominant (active) CAN differential typically ~1.5–3.5 V between CAN_H and CAN_L
  • Typical CAN bus termination resistance ~60 ohms measured across CAN_H and CAN_L (two 120Ω terminators in parallel)
  • Module supply voltage ~12 V (key ON), ground continuity near 0 ohms to chassis
  • Scan tool should show module responding with periodic messages/ECU ID when communication is healthy

Diagnostic algorithm

  1. Connect a diagnostic scanner and verify U0103 is current or stored; capture freeze frame and related U-codes.
  2. Attempt to communicate directly with the Gear Shift Control Module; note if the module is completely non-responsive or intermittently visible.
  3. Inspect for obvious damage at the module harness and connectors (bent pins, corrosion, moisture). Repair as needed.
  4. Verify battery voltage and inspect/replace any blown fuses or faulty relays that supply the module.
  5. Backprobe the module power and ground pins to confirm proper supply voltage and a good ground with key ON. Repair power/ground faults before proceeding.
  6. With ignition ON, measure CAN_H and CAN_L at the module connector. Compare to expected idle voltages and check for a short to battery or ground.
  7. Measure termination resistance across CAN_H and CAN_L at two locations; compare to expected ~60 ohms. Unplugging a connector may help isolate which segment has the fault.
  8. Wiggle harnesses and connectors while monitoring communication to reproduce intermittent failures; repair wiring or connector faults found.
  9. If wiring and power/ground are good and the bus appears healthy, consider updating module software or replacing the gear shift control module per manufacturer procedures. Program/configure replacement module as required.
  10. After repairs, clear codes and road-test to confirm the fault does not return. Re-scan to ensure other modules regained communication.

Likely causes

  • Damaged or disconnected CAN high/low wires to the gear shift control module
  • Faulty connector pins (bent, corroded or pushed out) at the module harness
  • Module lost power or ground (fuse or wiring fault)
  • Module internal failure (hardware/software) after a recent event (water intrusion, impact, or electrical surge)
  • Network termination resistance out of specification causing bus communications to fail

Fault status

⚠️ Status
Lost Communication With Gear Shift Control Module A — module not responding on vehicle communication network
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0101 U0121 U0122 U0146 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.
Send to email
Code

U0103

MERCEDES-BENZ U — Network/User

Lost Communication with Gear Shift Module

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

Causes

  • Open or shorted wiring on the vehicle communication bus (CAN/LIN) to the gear shift control module
  • Faulty gear shift control module (internal failure)
  • Missing or intermittent power or ground to the module
  • Corroded, loose or damaged connectors at the module or junctions
  • Blown fuse or failed relay supplying the module
  • Network termination or grounding problem (improper CAN termination, short to battery or ground)

Symptoms

  • Transmission/gear selector not responding or unable to change gears
  • MIL/Check Engine lamp or transmission warning lamp illuminated
  • Transmission may enter limp/backup mode (reduced shifting or fixed gear)
  • Transmission shift indicator/instrument cluster may show no data or erratic readouts
  • Other modules report multiple U-codes or loss of module data
  • No communication with the gear shift control module shown on a scan tool

What to check

  • Use a scan tool to attempt communication with the Gear Shift Control Module and read freeze frame and stored codes
  • Check for other U-codes that point to a wider bus failure (multiple modules non-communicative)
  • Visually inspect module connectors and harness for corrosion, damage, or water intrusion
  • Verify battery voltage and charging system condition (stable ~12–14.5 V with key on and engine running)
  • Verify fuses and relays for the gear shift control module power circuit
  • Measure power and ground at the module connector with a DVOM

Signal parameters

  • CAN bus idle voltages: CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V (both ~2.5 V when recessive)
  • Dominant (active) CAN differential typically ~1.5–3.5 V between CAN_H and CAN_L
  • Typical CAN bus termination resistance ~60 ohms measured across CAN_H and CAN_L (two 120Ω terminators in parallel)
  • Module supply voltage ~12 V (key ON), ground continuity near 0 ohms to chassis
  • Scan tool should show module responding with periodic messages/ECU ID when communication is healthy

Diagnostic algorithm

  1. Connect a diagnostic scanner and verify U0103 is current or stored; capture freeze frame and related U-codes.
  2. Attempt to communicate directly with the Gear Shift Control Module; note if the module is completely non-responsive or intermittently visible.
  3. Inspect for obvious damage at the module harness and connectors (bent pins, corrosion, moisture). Repair as needed.
  4. Verify battery voltage and inspect/replace any blown fuses or faulty relays that supply the module.
  5. Backprobe the module power and ground pins to confirm proper supply voltage and a good ground with key ON. Repair power/ground faults before proceeding.
  6. With ignition ON, measure CAN_H and CAN_L at the module connector. Compare to expected idle voltages and check for a short to battery or ground.
  7. Measure termination resistance across CAN_H and CAN_L at two locations; compare to expected ~60 ohms. Unplugging a connector may help isolate which segment has the fault.
  8. Wiggle harnesses and connectors while monitoring communication to reproduce intermittent failures; repair wiring or connector faults found.
  9. If wiring and power/ground are good and the bus appears healthy, consider updating module software or replacing the gear shift control module per manufacturer procedures. Program/configure replacement module as required.
  10. After repairs, clear codes and road-test to confirm the fault does not return. Re-scan to ensure other modules regained communication.

Likely causes

  • Damaged or disconnected CAN high/low wires to the gear shift control module
  • Faulty connector pins (bent, corroded or pushed out) at the module harness
  • Module lost power or ground (fuse or wiring fault)
  • Module internal failure (hardware/software) after a recent event (water intrusion, impact, or electrical surge)
  • Network termination resistance out of specification causing bus communications to fail

Fault status

⚠️ Status
Lost Communication With Gear Shift Control Module A — module not responding on vehicle communication network
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0101 U0121 U0122 U0146 U0155
856

Browse 856 MERCEDES-BENZ manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MERCEDES-BENZ

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

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