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Home / DTC / B2803 — No Response NM Message (AMP)

B2803 — No Response NM Message (AMP)

Detailed page for trouble code B2803.

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B2803

HYUNDAI B — Body

No Response NM Message (AMP)

Brand: HYUNDAI
Type: B — Body
AI status
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Page language: EN

Causes

  • AMP module not powered (blown fuse, relay, or wiring fault)
  • Poor or missing ground at the AMP
  • Damaged or disconnected connector(s) to the AMP
  • Open, short, or high resistance in the network (CAN/LIN) wiring between AMP and main bus
  • Corroded pins or water intrusion in connectors
  • AMP module internal failure

Symptoms

  • Audio amplifier (AMP) inoperative or no sound from speakers
  • Other modules show communication-related warnings or errors
  • AM/FM, navigation, or infotainment features missing or intermittent
  • Battery drain (if AMP stuck awake) or vehicle not entering sleep
  • DTCs for lost communication present in other modules

What to check

  • Inspect relevant fuses and relays for the AMP; verify fuse continuity and proper relay operation
  • Visually inspect AMP connectors for corrosion, dirt, bent pins, or water intrusion
  • Verify AMP power and ground voltages at the connector with key ON and engine OFF
  • Scan the vehicle network to see whether the AMP is present on the bus and check for NM / keep-alive messages
  • Measure CAN/LIN bus voltages (idle voltages for CAN high/low ~2.5 V) and look for excessive resistance or shorts to battery/ground
  • Check for Diagnostic Trouble Codes in other modules (BCM, head unit, gateway) that indicate bus issues

Signal parameters

  • Expected NM message periodicity (typically once per second or specified by manufacturer)
  • CAN bus idle voltages: CAN_H ~2.5 V, CAN_L ~2.5 V (differential ~0 V idle); active differential ~2.5 V
  • LIN bus voltage levels and expected header/wake pattern (if AMP on LIN)
  • Bus termination resistance (typically ~60 ohms for CAN between high/low)
  • Number of error frames on bus and frequency of lost frames
  • Module VIN/address presence on network (seen by scan tool)

Diagnostic algorithm

  1. Retrieve freeze frame and full DTC list from all modules with a capable scan tool; note any related U- or B- codes.
  2. Verify vehicle battery voltage is within specification to rule out low-voltage related communication failures.
  3. Inspect AMP connector and wiring for obvious damage, corrosion, or loose terminals. Repair if found.
  4. Check AMP supply fuse(s) and relay; verify battery +12V at the AMP power pin with key ON/ACC. Replace faulty fuses/relays.
  5. Verify good ground(s) at the AMP (measure
  6. With scan tool, attempt to communicate with AMP. If module not present, monitor CAN/LIN traffic to see if the AMP transmits NM messages. Note message IDs and frequency.
  7. Measure CAN_H and CAN_L (or LIN) at the AMP connector while operating the network. Look for missing activity or short to supply/ground.
  8. If suspect wiring fault between AMP and gateway/BCM, perform continuity and short-to-power/ground tests on network and power wires with connectors disconnected and battery removed if required by procedure.
  9. If wiring and power/ground are good but no messages are transmitted, consider AMP internal fault. Reprogramming may be required after replacement; check TSBs/UPDATES before replacement.
  10. If AMP is replaced, clear DTCs and verify on-road/electrical operation and that NM messages are present and stable. Confirm related modules no longer report communication faults.

Likely causes

  • Blown fuse or removed power connector to the AMP
  • Loose or corroded ground at the AMP
  • Broken or shorted network wire (CAN high/low or LIN) to the AMP
  • Internal AMP hardware failure preventing transmission
  • Gateway or BCM not forwarding NM messages

Fault status

⚠️ Status
No response from AMP: expected Network Management (NM) message not received — communication timeout or missing module messages on vehicle network.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

U0100 U0140 U0121 B2800 B2801
371

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