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Home / DTC / U0138 — Lost Communication With All Terrain Control Module

U0138 — Lost Communication With All Terrain Control Module

Detailed page for trouble code U0138.

33,912codes
59brands
11,451generic
22,461specific
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Code

U0138

Generic U — Network/User

Lost Communication With All Terrain Control Module

Brand: Generic
Type: U — Network/User
Views: UK: 22 EN: 46 RU: 27
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or short in CAN wiring (CAN High / CAN Low) to the ATCM
  • Faulty or corroded connector pins at the ATCM or junctions
  • Blown fuse or missing power/ground to the ATCM
  • Failed ATCM (internal electronics)
  • Faulty module elsewhere on same network dragging down the bus
  • Improper or missing CAN bus termination

Symptoms

  • Warning lamp or message related to All Terrain system
  • Loss of All Terrain features or drive-mode selection
  • One or more control modules reporting U0138 or other U0XXX codes
  • Intermittent operation of terrain features or unpredictable behavior
  • No response from ATCM when queried with diagnostic tool

What to check

  • Read stored codes and freeze frame / occurrence count; note time and conditions
  • Check for other network communication codes (U0100, U0115, etc.)
  • Verify battery voltage (key on, engine off) and charging system
  • Inspect fuses and relays related to ATCM power and ignition feed
  • Visually inspect connectors and wiring at ATCM and common junctions
  • Attempt to communicate with ATCM via scan tool; note module presence/absence

Signal parameters

  • Battery/Module supply (VBATT) expected: ~11–14.5 V (key on)
  • CAN bus idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each)
  • CAN bus dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (typical differential ≈ 2.0 V)
  • Bus termination: two 120 Ω resistors in parallel ≈ 60 Ω measured between CAN_H and CAN_L
  • Common CAN bit rates: 250 kbps or 500 kbps (vehicle-specific)

Diagnostic algorithm

  1. Retrieve manufacturer-specific freeze frame and all U0 codes. Note if code is current or history.
  2. Confirm other modules on same CAN network are communicating. If multiple modules lost, suspect bus power/termination.
  3. Verify battery voltage and check fuses/relays that supply the ATCM. Repair any blown fuses and retest.
  4. With ignition ON (engine OFF), inspect and wiggle ATCM connector for corrosion, bent pins, or loose terminals. Repair as needed.
  5. Measure VBATT and ground at the ATCM connector. If no power or poor ground, trace and repair circuit.
  6. Measure CAN_H and CAN_L at the ATCM connector with a digital multimeter: expect ~2.5 V each (recessive). If voltages abnormal, isolate short/open.
  7. Measure resistance between CAN_H and CAN_L with ignition OFF; expect ≈ 60 Ω. If open or very low, inspect termination and modules.
  8. Use a scope or CAN bus analyzer to view waveform integrity and network traffic. Look for missing frames, bus errors, or a node holding the bus dominant.
  9. Disconnect suspected faulty modules one at a time (or isolate wiring sections) to identify a module that may be pulling the bus down.
  10. After wiring and power/ground verified good, attempt to reinitialize or wake the ATCM (follow manufacturer procedure). Clear codes and retest for reoccurrence.
  11. If wiring and bus are confirmed good and ATCM still unresponsive, replace the ATCM or update module software per manufacturer instructions. Reprogram if required.
  12. After repair, perform full scan and functional test of All Terrain functions and confirm no related U0 codes return.

Likely causes

  • Damaged wiring harness to ATCM (chafing, rodent damage, pinched)
  • Loose, bent or corroded pins in ATCM connector
  • Blown fuse or bad ground at module
  • CANH/CANL short to battery or ground
  • Missing 60 ohm effective bus termination (open or extra resistor)
  • ATCM hardware failure or failed transceiver

Fault status

⚠️ Status
Lost communication with All Terrain Control Module — no valid CAN messages received from the ATCM. Code set when module fails to respond on its network.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-4.0 hours

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Code

U0138

HYUNDAI U — Network/User

Lost Communication With All Terrain Control Module

Brand: HYUNDAI
Type: U — Network/User
Views: UK: 24 EN: 41 RU: 24
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or short in CAN wiring (CAN High / CAN Low) to the ATCM
  • Faulty or corroded connector pins at the ATCM or junctions
  • Blown fuse or missing power/ground to the ATCM
  • Failed ATCM (internal electronics)
  • Faulty module elsewhere on same network dragging down the bus
  • Improper or missing CAN bus termination

Symptoms

  • Warning lamp or message related to All Terrain system
  • Loss of All Terrain features or drive-mode selection
  • One or more control modules reporting U0138 or other U0XXX codes
  • Intermittent operation of terrain features or unpredictable behavior
  • No response from ATCM when queried with diagnostic tool

What to check

  • Read stored codes and freeze frame / occurrence count; note time and conditions
  • Check for other network communication codes (U0100, U0115, etc.)
  • Verify battery voltage (key on, engine off) and charging system
  • Inspect fuses and relays related to ATCM power and ignition feed
  • Visually inspect connectors and wiring at ATCM and common junctions
  • Attempt to communicate with ATCM via scan tool; note module presence/absence

Signal parameters

  • Battery/Module supply (VBATT) expected: ~11–14.5 V (key on)
  • CAN bus idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each)
  • CAN bus dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (typical differential ≈ 2.0 V)
  • Bus termination: two 120 Ω resistors in parallel ≈ 60 Ω measured between CAN_H and CAN_L
  • Common CAN bit rates: 250 kbps or 500 kbps (vehicle-specific)

Diagnostic algorithm

  1. Retrieve manufacturer-specific freeze frame and all U0 codes. Note if code is current or history.
  2. Confirm other modules on same CAN network are communicating. If multiple modules lost, suspect bus power/termination.
  3. Verify battery voltage and check fuses/relays that supply the ATCM. Repair any blown fuses and retest.
  4. With ignition ON (engine OFF), inspect and wiggle ATCM connector for corrosion, bent pins, or loose terminals. Repair as needed.
  5. Measure VBATT and ground at the ATCM connector. If no power or poor ground, trace and repair circuit.
  6. Measure CAN_H and CAN_L at the ATCM connector with a digital multimeter: expect ~2.5 V each (recessive). If voltages abnormal, isolate short/open.
  7. Measure resistance between CAN_H and CAN_L with ignition OFF; expect ≈ 60 Ω. If open or very low, inspect termination and modules.
  8. Use a scope or CAN bus analyzer to view waveform integrity and network traffic. Look for missing frames, bus errors, or a node holding the bus dominant.
  9. Disconnect suspected faulty modules one at a time (or isolate wiring sections) to identify a module that may be pulling the bus down.
  10. After wiring and power/ground verified good, attempt to reinitialize or wake the ATCM (follow manufacturer procedure). Clear codes and retest for reoccurrence.
  11. If wiring and bus are confirmed good and ATCM still unresponsive, replace the ATCM or update module software per manufacturer instructions. Reprogram if required.
  12. After repair, perform full scan and functional test of All Terrain functions and confirm no related U0 codes return.

Likely causes

  • Damaged wiring harness to ATCM (chafing, rodent damage, pinched)
  • Loose, bent or corroded pins in ATCM connector
  • Blown fuse or bad ground at module
  • CANH/CANL short to battery or ground
  • Missing 60 ohm effective bus termination (open or extra resistor)
  • ATCM hardware failure or failed transceiver

Fault status

⚠️ Status
Lost communication with All Terrain Control Module — no valid CAN messages received from the ATCM. Code set when module fails to respond on its network.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-4.0 hours

Similar codes

U0100 U0115 U0121 U0155 U0142
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 :)
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Code

U0138

LAND ROVER U — Network/User

Lost communication with the terrain control module

Brand: LAND ROVER
Type: U — Network/User
Views: UK: 18 EN: 41 RU: 19
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or short in CAN wiring (CAN High / CAN Low) to the ATCM
  • Faulty or corroded connector pins at the ATCM or junctions
  • Blown fuse or missing power/ground to the ATCM
  • Failed ATCM (internal electronics)
  • Faulty module elsewhere on same network dragging down the bus
  • Improper or missing CAN bus termination

Symptoms

  • Warning lamp or message related to All Terrain system
  • Loss of All Terrain features or drive-mode selection
  • One or more control modules reporting U0138 or other U0XXX codes
  • Intermittent operation of terrain features or unpredictable behavior
  • No response from ATCM when queried with diagnostic tool

What to check

  • Read stored codes and freeze frame / occurrence count; note time and conditions
  • Check for other network communication codes (U0100, U0115, etc.)
  • Verify battery voltage (key on, engine off) and charging system
  • Inspect fuses and relays related to ATCM power and ignition feed
  • Visually inspect connectors and wiring at ATCM and common junctions
  • Attempt to communicate with ATCM via scan tool; note module presence/absence

Signal parameters

  • Battery/Module supply (VBATT) expected: ~11–14.5 V (key on)
  • CAN bus idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (each)
  • CAN bus dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (typical differential ≈ 2.0 V)
  • Bus termination: two 120 Ω resistors in parallel ≈ 60 Ω measured between CAN_H and CAN_L
  • Common CAN bit rates: 250 kbps or 500 kbps (vehicle-specific)

Diagnostic algorithm

  1. Retrieve manufacturer-specific freeze frame and all U0 codes. Note if code is current or history.
  2. Confirm other modules on same CAN network are communicating. If multiple modules lost, suspect bus power/termination.
  3. Verify battery voltage and check fuses/relays that supply the ATCM. Repair any blown fuses and retest.
  4. With ignition ON (engine OFF), inspect and wiggle ATCM connector for corrosion, bent pins, or loose terminals. Repair as needed.
  5. Measure VBATT and ground at the ATCM connector. If no power or poor ground, trace and repair circuit.
  6. Measure CAN_H and CAN_L at the ATCM connector with a digital multimeter: expect ~2.5 V each (recessive). If voltages abnormal, isolate short/open.
  7. Measure resistance between CAN_H and CAN_L with ignition OFF; expect ≈ 60 Ω. If open or very low, inspect termination and modules.
  8. Use a scope or CAN bus analyzer to view waveform integrity and network traffic. Look for missing frames, bus errors, or a node holding the bus dominant.
  9. Disconnect suspected faulty modules one at a time (or isolate wiring sections) to identify a module that may be pulling the bus down.
  10. After wiring and power/ground verified good, attempt to reinitialize or wake the ATCM (follow manufacturer procedure). Clear codes and retest for reoccurrence.
  11. If wiring and bus are confirmed good and ATCM still unresponsive, replace the ATCM or update module software per manufacturer instructions. Reprogram if required.
  12. After repair, perform full scan and functional test of All Terrain functions and confirm no related U0 codes return.

Likely causes

  • Damaged wiring harness to ATCM (chafing, rodent damage, pinched)
  • Loose, bent or corroded pins in ATCM connector
  • Blown fuse or bad ground at module
  • CANH/CANL short to battery or ground
  • Missing 60 ohm effective bus termination (open or extra resistor)
  • ATCM hardware failure or failed transceiver

Fault status

⚠️ Status
Lost communication with All Terrain Control Module — no valid CAN messages received from the ATCM. Code set when module fails to respond on its network.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-4.0 hours

Similar codes

U0100 U0115 U0121 U0155 U0142
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

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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