Code
U0549
Generic
U — Network/User
Invalid Data Received From Remote Accessory Module
AI status
Completed
Completed
100%
Causes
- Corrupt or out-of-spec CAN/FlexRay/LIN messages from the Remote Accessory Module
- Faulty Remote Accessory Module (software or hardware failure)
- Intermittent or open/shorted wiring or poor connector connection between module and vehicle data bus
- Bus termination or grounding issues (incorrect resistance or missing ground)
- Low battery or unstable supply voltage affecting module operation
- Aftermarket accessory or device interfering with the network
Symptoms
- MIL (malfunction indicator lamp) or communication warning lamp illuminated
- Certain accessory functions (remote controls, keyless entry, interior lighting, etc.) do not work or behave erratically
- Other network modules report related U-codes or loss-of-communication codes
- Stored freeze frame or event data showing network anomalies
- Possible network-wide intermittent faults or sporadic message errors
What to check
- Read all stored and pending DTCs and freeze frame data from all modules; note any other U-codes
- Check vehicle battery state-of-charge and charging system voltage (12.0–14.7 V nominal while running)
- Inspect connectors, wiring harness and pins at the Remote Accessory Module and gateway for corrosion, damage or loose terminals
- Use a scan tool to view live network messages, module presence, and any invalid/garbled payloads
- Measure CAN bus termination resistance (two 120 ohm resistors in parallel ≈ 60 ohms between CAN_H and CAN_L) with ignition off
- Probe CAN_H and CAN_L with an oscilloscope or lab scope to check idle voltages and signal integrity
Signal parameters
- CAN idle voltages: CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 1.5–2.5 V; differential recessive ≈ 0 V, dominant ≈ 2 V
- Expected bus termination: total ≈ 60 ohms between CAN_H and CAN_L
- Common CAN bit rates: 125 kbps, 250 kbps, 500 kbps — confirm vehicle's network speed
- Message periodicity: check expected message intervals (e.g., 10–1000 ms depending on message)
- Data length/code fields: verify that received payload length and checksum/CRC match expected values
- Message ID presence: verify ID of RAM messages appears and does not conflict with other nodes
Diagnostic algorithm
- Record all codes, freeze frame, and current module status using a capable scan tool. Note related U-codes.
- Verify battery voltage and health. Recharge or connect a stable supply if low before testing communications.
- Perform a visual inspection of wiring/connectors to the Remote Accessory Module and gateway. Repair any damage or corrosion.
- Clear the codes, then attempt to reproduce. If U0549 returns immediately or intermittently, capture live bus traffic.
- Using a scan tool, confirm the RAM is present on the network and compare its message IDs/payloads against expected values or another known-good vehicle if available.
- Measure termination resistance between CAN_H and CAN_L (≈60 ohms). If out of range, locate missing/extra termination or damaged wiring.
- Probe CAN lines with an oscilloscope while exercising the affected accessories to spot noise, missing edges, dominant shorts, or voltage offsets.
- Disconnect suspected aftermarket devices and retest. If removal cures the issue, inspect or replace the aftermarket device.
- If wiring and bus integrity are good, verify module software/calibration levels. Reflash or reprogram the RAM with correct OEM software if required.
- If the module continues to send invalid data after reprogramming and wiring checks, replace the Remote Accessory Module and retest.
- After repairs, clear codes and road-test to confirm no reoccurrence and check for related stored codes in other modules.
Likely causes
- Damaged connector pins or corroded terminals at the RAM or gateway
- CAN high/low wiring shorted to each other or to battery/ground near the RAM
- Poor battery voltage or weak charge during module communication
- Module firmware mismatch after recent software update or replacement
- Intermittent ground or power feed to the RAM causing sporadic bad packets
Fault status
Status
Invalid data received from Remote Accessory Module — network message payload, timing, or checksum is outside expected parameters; may indicate corrupted messages, wiring fault, module software mismatch, or failed accessory module.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Repair manuals
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Code
U0549
HYUNDAI
U — Network/User
Invalid Data Received From Remote Accessory Module
AI status
Completed
Completed
100%
Causes
- Corrupt or out-of-spec CAN/FlexRay/LIN messages from the Remote Accessory Module
- Faulty Remote Accessory Module (software or hardware failure)
- Intermittent or open/shorted wiring or poor connector connection between module and vehicle data bus
- Bus termination or grounding issues (incorrect resistance or missing ground)
- Low battery or unstable supply voltage affecting module operation
- Aftermarket accessory or device interfering with the network
Symptoms
- MIL (malfunction indicator lamp) or communication warning lamp illuminated
- Certain accessory functions (remote controls, keyless entry, interior lighting, etc.) do not work or behave erratically
- Other network modules report related U-codes or loss-of-communication codes
- Stored freeze frame or event data showing network anomalies
- Possible network-wide intermittent faults or sporadic message errors
What to check
- Read all stored and pending DTCs and freeze frame data from all modules; note any other U-codes
- Check vehicle battery state-of-charge and charging system voltage (12.0–14.7 V nominal while running)
- Inspect connectors, wiring harness and pins at the Remote Accessory Module and gateway for corrosion, damage or loose terminals
- Use a scan tool to view live network messages, module presence, and any invalid/garbled payloads
- Measure CAN bus termination resistance (two 120 ohm resistors in parallel ≈ 60 ohms between CAN_H and CAN_L) with ignition off
- Probe CAN_H and CAN_L with an oscilloscope or lab scope to check idle voltages and signal integrity
Signal parameters
- CAN idle voltages: CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 1.5–2.5 V; differential recessive ≈ 0 V, dominant ≈ 2 V
- Expected bus termination: total ≈ 60 ohms between CAN_H and CAN_L
- Common CAN bit rates: 125 kbps, 250 kbps, 500 kbps — confirm vehicle's network speed
- Message periodicity: check expected message intervals (e.g., 10–1000 ms depending on message)
- Data length/code fields: verify that received payload length and checksum/CRC match expected values
- Message ID presence: verify ID of RAM messages appears and does not conflict with other nodes
Diagnostic algorithm
- Record all codes, freeze frame, and current module status using a capable scan tool. Note related U-codes.
- Verify battery voltage and health. Recharge or connect a stable supply if low before testing communications.
- Perform a visual inspection of wiring/connectors to the Remote Accessory Module and gateway. Repair any damage or corrosion.
- Clear the codes, then attempt to reproduce. If U0549 returns immediately or intermittently, capture live bus traffic.
- Using a scan tool, confirm the RAM is present on the network and compare its message IDs/payloads against expected values or another known-good vehicle if available.
- Measure termination resistance between CAN_H and CAN_L (≈60 ohms). If out of range, locate missing/extra termination or damaged wiring.
- Probe CAN lines with an oscilloscope while exercising the affected accessories to spot noise, missing edges, dominant shorts, or voltage offsets.
- Disconnect suspected aftermarket devices and retest. If removal cures the issue, inspect or replace the aftermarket device.
- If wiring and bus integrity are good, verify module software/calibration levels. Reflash or reprogram the RAM with correct OEM software if required.
- If the module continues to send invalid data after reprogramming and wiring checks, replace the Remote Accessory Module and retest.
- After repairs, clear codes and road-test to confirm no reoccurrence and check for related stored codes in other modules.
Likely causes
- Damaged connector pins or corroded terminals at the RAM or gateway
- CAN high/low wiring shorted to each other or to battery/ground near the RAM
- Poor battery voltage or weak charge during module communication
- Module firmware mismatch after recent software update or replacement
- Intermittent ground or power feed to the RAM causing sporadic bad packets
Fault status
Status
Invalid data received from Remote Accessory Module — network message payload, timing, or checksum is outside expected parameters; may indicate corrupted messages, wiring fault, module software mismatch, or failed accessory module.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Repair manuals
Manual library for HYUNDAI
371
Browse 371 HYUNDAI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
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