Code
U0241
Generic
U — Network/User
Lost Communication With Headlamp Control Module A
Views:
UK: 21
EN: 25
RU: 31
AI status
Completed
Completed
100%
Causes
- Faulty Headlamp Control Module (HCM A)
- Blown fuse or removed power/ignition feed to the HCM
- Poor ground connection at the HCM
- Damaged or corroded connector pins at the HCM
- Broken, shorted or open wiring in CAN/LIN communication lines
- CAN bus termination problem (open or shorted termination resistor)
Symptoms
- Malfunctioning or non-operational headlamps (low/high beam or DRL)
- Warning message or lamp indicating headlamp or network fault
- Loss of adaptive lighting, leveling or auto headlamp functions
- Multiple communication-related U-codes stored
- Intermittent headlamp operation or flicker
- No response from Headlamp Control Module when scanned
What to check
- Scan the vehicle with a capable scan tool; note U0241 and any other U-codes
- Attempt to communicate with the Headlamp Control Module using the scanner
- Inspect fuses and relays related to headlamp and module power
- Visually inspect module connector for corrosion, bent pins, or water intrusion
- Check battery voltage and charging system (11–14.5 V expected)
- Verify good chassis/engine ground and module ground circuit continuity
Signal parameters
- CAN bus recessive voltage: ~2.5 V on CANH and CANL (key ON, idle bus)
- CAN dominant state: CANH ~3.5 V, CANL ~1.5 V (differential ~2.0 V) during activity
- Differential CAN voltage while active: ~1.5–2.5 V depending on bus load
- Typical CAN bus termination: ~60 Ω measured between CANH and CANL at two terminators in parallel
- Valid module supply: battery voltage between ~11–14.5 V at the HCM power pin with IGN on
- Module ground loop resistance: low, typically
Diagnostic algorithm
- Record freeze frame data and all stored network fault codes with a scan tool. Note any other U-codes present.
- Attempt to communicate directly with Headlamp Control Module A. If it responds intermittently or not at all, proceed.
- Check vehicle battery voltage and ensure stable supply (repair/charge if low).
- Inspect fuses/relays for headlamp/module circuits; replace any blown fuses and re-test communication.
- Visually inspect the HCM connector and harness for corrosion, bent pins, water ingress, insulation damage, or recent repair splices.
- Backprobe the module connector: verify constant battery/power feed and switched/IGN feed (where present) and a solid ground reference with key ON.
- Measure CANH/CANL voltages with key ON at the module connector. Expect ~2.5 V on each with an idle bus. If voltages are abnormal, trace wiring for short to battery/ground or open circuit.
- With a scope (preferred) or multimeter, check for CAN bus activity while cranking/accessory on. Verify proper dominant/recessive transitions and differential voltage. If the bus is silent, isolate which module is missing.
- Check CAN termination resistance (~60 Ω). Remove modules as required to isolate a shorted/faulty device that may be pulling the bus down.
- Wiggle test harness and connectors while monitoring communication to reproduce intermittent faults—do not wiggle near moving parts or hot components.
- If wiring, connectors, or power/ground faults are found, repair or replace damaged wiring or connectors and retest.
- If wiring and power/ground check OK but module will not respond, verify module part number and software level; reprogram or replace module per manufacturer procedure if required.
Likely causes
- Loose/corroded connector or poor ground at the headlamp control module
- Blown fuse or lost power feed to the module
- Intermittent CANH/CANL connection (open/short) due to damaged wiring
- Faulty headlamp control module
- Another module causing the CAN bus to be off or flooding the bus
Fault status
Status
Lost Communication With Headlamp Control Module A — module not responding on vehicle network (CAN/LIN).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
U0241
HYUNDAI
U — Network/User
Lost Communication With Headlamp Control Module “A”
Views:
UK: 14
EN: 12
RU: 25
AI status
Completed
Completed
100%
Causes
- Faulty Headlamp Control Module (HCM A)
- Blown fuse or removed power/ignition feed to the HCM
- Poor ground connection at the HCM
- Damaged or corroded connector pins at the HCM
- Broken, shorted or open wiring in CAN/LIN communication lines
- CAN bus termination problem (open or shorted termination resistor)
Symptoms
- Malfunctioning or non-operational headlamps (low/high beam or DRL)
- Warning message or lamp indicating headlamp or network fault
- Loss of adaptive lighting, leveling or auto headlamp functions
- Multiple communication-related U-codes stored
- Intermittent headlamp operation or flicker
- No response from Headlamp Control Module when scanned
What to check
- Scan the vehicle with a capable scan tool; note U0241 and any other U-codes
- Attempt to communicate with the Headlamp Control Module using the scanner
- Inspect fuses and relays related to headlamp and module power
- Visually inspect module connector for corrosion, bent pins, or water intrusion
- Check battery voltage and charging system (11–14.5 V expected)
- Verify good chassis/engine ground and module ground circuit continuity
Signal parameters
- CAN bus recessive voltage: ~2.5 V on CANH and CANL (key ON, idle bus)
- CAN dominant state: CANH ~3.5 V, CANL ~1.5 V (differential ~2.0 V) during activity
- Differential CAN voltage while active: ~1.5–2.5 V depending on bus load
- Typical CAN bus termination: ~60 Ω measured between CANH and CANL at two terminators in parallel
- Valid module supply: battery voltage between ~11–14.5 V at the HCM power pin with IGN on
- Module ground loop resistance: low, typically
Diagnostic algorithm
- Record freeze frame data and all stored network fault codes with a scan tool. Note any other U-codes present.
- Attempt to communicate directly with Headlamp Control Module A. If it responds intermittently or not at all, proceed.
- Check vehicle battery voltage and ensure stable supply (repair/charge if low).
- Inspect fuses/relays for headlamp/module circuits; replace any blown fuses and re-test communication.
- Visually inspect the HCM connector and harness for corrosion, bent pins, water ingress, insulation damage, or recent repair splices.
- Backprobe the module connector: verify constant battery/power feed and switched/IGN feed (where present) and a solid ground reference with key ON.
- Measure CANH/CANL voltages with key ON at the module connector. Expect ~2.5 V on each with an idle bus. If voltages are abnormal, trace wiring for short to battery/ground or open circuit.
- With a scope (preferred) or multimeter, check for CAN bus activity while cranking/accessory on. Verify proper dominant/recessive transitions and differential voltage. If the bus is silent, isolate which module is missing.
- Check CAN termination resistance (~60 Ω). Remove modules as required to isolate a shorted/faulty device that may be pulling the bus down.
- Wiggle test harness and connectors while monitoring communication to reproduce intermittent faults—do not wiggle near moving parts or hot components.
- If wiring, connectors, or power/ground faults are found, repair or replace damaged wiring or connectors and retest.
- If wiring and power/ground check OK but module will not respond, verify module part number and software level; reprogram or replace module per manufacturer procedure if required.
Likely causes
- Loose/corroded connector or poor ground at the headlamp control module
- Blown fuse or lost power feed to the module
- Intermittent CANH/CANL connection (open/short) due to damaged wiring
- Faulty headlamp control module
- Another module causing the CAN bus to be off or flooding the bus
Fault status
Status
Lost Communication With Headlamp Control Module A — module not responding on vehicle network (CAN/LIN).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
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Code
U0241
LAND ROVER
U — Network/User
Lost communication with headlight control module A
Views:
UK: 7
EN: 8
RU: 11
AI status
Completed
Completed
100%
Causes
- Faulty Headlamp Control Module (HCM A)
- Blown fuse or removed power/ignition feed to the HCM
- Poor ground connection at the HCM
- Damaged or corroded connector pins at the HCM
- Broken, shorted or open wiring in CAN/LIN communication lines
- CAN bus termination problem (open or shorted termination resistor)
Symptoms
- Malfunctioning or non-operational headlamps (low/high beam or DRL)
- Warning message or lamp indicating headlamp or network fault
- Loss of adaptive lighting, leveling or auto headlamp functions
- Multiple communication-related U-codes stored
- Intermittent headlamp operation or flicker
- No response from Headlamp Control Module when scanned
What to check
- Scan the vehicle with a capable scan tool; note U0241 and any other U-codes
- Attempt to communicate with the Headlamp Control Module using the scanner
- Inspect fuses and relays related to headlamp and module power
- Visually inspect module connector for corrosion, bent pins, or water intrusion
- Check battery voltage and charging system (11–14.5 V expected)
- Verify good chassis/engine ground and module ground circuit continuity
Signal parameters
- CAN bus recessive voltage: ~2.5 V on CANH and CANL (key ON, idle bus)
- CAN dominant state: CANH ~3.5 V, CANL ~1.5 V (differential ~2.0 V) during activity
- Differential CAN voltage while active: ~1.5–2.5 V depending on bus load
- Typical CAN bus termination: ~60 Ω measured between CANH and CANL at two terminators in parallel
- Valid module supply: battery voltage between ~11–14.5 V at the HCM power pin with IGN on
- Module ground loop resistance: low, typically
Diagnostic algorithm
- Record freeze frame data and all stored network fault codes with a scan tool. Note any other U-codes present.
- Attempt to communicate directly with Headlamp Control Module A. If it responds intermittently or not at all, proceed.
- Check vehicle battery voltage and ensure stable supply (repair/charge if low).
- Inspect fuses/relays for headlamp/module circuits; replace any blown fuses and re-test communication.
- Visually inspect the HCM connector and harness for corrosion, bent pins, water ingress, insulation damage, or recent repair splices.
- Backprobe the module connector: verify constant battery/power feed and switched/IGN feed (where present) and a solid ground reference with key ON.
- Measure CANH/CANL voltages with key ON at the module connector. Expect ~2.5 V on each with an idle bus. If voltages are abnormal, trace wiring for short to battery/ground or open circuit.
- With a scope (preferred) or multimeter, check for CAN bus activity while cranking/accessory on. Verify proper dominant/recessive transitions and differential voltage. If the bus is silent, isolate which module is missing.
- Check CAN termination resistance (~60 Ω). Remove modules as required to isolate a shorted/faulty device that may be pulling the bus down.
- Wiggle test harness and connectors while monitoring communication to reproduce intermittent faults—do not wiggle near moving parts or hot components.
- If wiring, connectors, or power/ground faults are found, repair or replace damaged wiring or connectors and retest.
- If wiring and power/ground check OK but module will not respond, verify module part number and software level; reprogram or replace module per manufacturer procedure if required.
Likely causes
- Loose/corroded connector or poor ground at the headlamp control module
- Blown fuse or lost power feed to the module
- Intermittent CANH/CANL connection (open/short) due to damaged wiring
- Faulty headlamp control module
- Another module causing the CAN bus to be off or flooding the bus
Fault status
Status
Lost Communication With Headlamp Control Module A — module not responding on vehicle network (CAN/LIN).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop Manual199,00 UAH
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Workshop Manual199,00 UAH
Land Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)
Workshop Manual199,00 UAH
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
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Send to email