Code
U1004
HYUNDAI
U — Network/User
Temperature Sensor Signal Error in Tunner and Amplifier | Lost Communication with Hybrid Powertrain Control Module (H-CAN)
Views:
UK: 11
EN: 43
RU: 16
AI status
Completed
Completed
100%
Causes
- Poor or corroded connector at tuner/amplifier or hybrid powertrain control module (HPCM)
- Damaged or chafed wiring harness (short to voltage or ground, open circuit)
- Failed temperature sensor (NTC/thermistor) inside tuner/amplifier
- Faulty tuner or amplifier module electronics
- H‑CAN bus fault (open, short, incorrect termination, high resistance)
- Blown fuse or lost power/ground to module
Symptoms
- MIL (malfunction indicator lamp) or warning lights illuminated
- Radio/tuner or amplifier may show errors or disable certain features
- Hybrid system messages or degraded hybrid operation if HPCM communication lost
- Multiple U‑codes or communication errors present on network scan
- Intermittent functionality or no communication with HPCM from scan tool
What to check
- Read freeze frame and full module list with a capable scan tool; note related U codes
- Inspect connectors at tuner/amplifier, HPCM and along H‑CAN for corrosion, damage or loose pins
- Check main fuses and power/ground circuits for the audio module and HPCM
- Measure battery voltage and verify stable supply while testing
- Verify CAN bus idle voltages and termination resistance
- Wiggle harness and connectors while monitoring communication for intermittent faults
Signal parameters
- CAN bus idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (both); dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V
- Typical CAN termination: ≈ 60 Ω measured across CAN_H and CAN_L (two 120 Ω in parallel)
- Temperature sensor (thermistor) behaves as NTC: resistance decreases as temperature rises (verify exact values with manufacturer spec)
- Module supply voltage: battery voltage (approx. 12 V nominal) present at module power pin
- Expect stable bus traffic with regular CAN frames when communication is healthy
Diagnostic algorithm
- Use a scan tool to record all active and stored codes and any freeze‑frame data. Note if multiple modules report U codes.
- Verify vehicle battery voltage is healthy and stable. Poor battery can cause network issues.
- Visually inspect connectors and wiring to the tuner/amplifier and HPCM; repair any corrosion, bent pins or damage.
- Check fuses and module power/ground circuits for continuity and correct voltage.
- With key on (engine off), measure CAN_H and CAN_L at the tuner/amplifier and HPCM connectors. Compare to expected idle and dominant voltages.
- Measure termination resistance across CAN_H and CAN_L (engine off). Expect ~60 Ω. If open or very low, address termination or short.
- If CAN voltages or termination are abnormal, trace and repair wiring (short to Vb/ground or open).
- Test the temperature sensor circuit at the tuner/amplifier: measure sensor resistance or voltage signal and compare to spec. If out of range, replace sensor/module.
- Perform a wiggle test of harnesses while monitoring live data/communication to find intermittent faults.
- If wiring and sensor check good, update module software if available and clear codes. Re-scan and road test to confirm repair.
- If communication cannot be restored after electrical checks, consider replacing the failed module (tuner/amplifier or HPCM) following manufacturer procedures.
Likely causes
- Intermittent or corroded connector at the tuner/amplifier or HPCM
- CAN bus wiring fault (open or short between CAN_H and CAN_L or to battery/ground)
- Failed tuner/amplifier temperature sensor or amplifier module
- Loss of power or ground to the HPCM or audio module
Fault status
Status
Temperature sensor signal error reported by tuner/amplifier and/or lost communication with Hybrid Powertrain Control Module on H‑CAN. Indicates a sensor, module, power/ground, or CAN network fault requiring electrical and communication checks.
Repair difficulty: Medium
Diagnostic time: 1.0 - 3.0 hours
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Code
U1004
Other
U — Network/User
SCP (J1850) Invalid or Missing Data for EEC Programming
Views:
UK: 12
EN: 54
RU: 25
AI status
Completed
Completed
100%
Causes
- Poor or corroded connector at tuner/amplifier or hybrid powertrain control module (HPCM)
- Damaged or chafed wiring harness (short to voltage or ground, open circuit)
- Failed temperature sensor (NTC/thermistor) inside tuner/amplifier
- Faulty tuner or amplifier module electronics
- H‑CAN bus fault (open, short, incorrect termination, high resistance)
- Blown fuse or lost power/ground to module
Symptoms
- MIL (malfunction indicator lamp) or warning lights illuminated
- Radio/tuner or amplifier may show errors or disable certain features
- Hybrid system messages or degraded hybrid operation if HPCM communication lost
- Multiple U‑codes or communication errors present on network scan
- Intermittent functionality or no communication with HPCM from scan tool
What to check
- Read freeze frame and full module list with a capable scan tool; note related U codes
- Inspect connectors at tuner/amplifier, HPCM and along H‑CAN for corrosion, damage or loose pins
- Check main fuses and power/ground circuits for the audio module and HPCM
- Measure battery voltage and verify stable supply while testing
- Verify CAN bus idle voltages and termination resistance
- Wiggle harness and connectors while monitoring communication for intermittent faults
Signal parameters
- CAN bus idle (recessive): CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (both); dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V
- Typical CAN termination: ≈ 60 Ω measured across CAN_H and CAN_L (two 120 Ω in parallel)
- Temperature sensor (thermistor) behaves as NTC: resistance decreases as temperature rises (verify exact values with manufacturer spec)
- Module supply voltage: battery voltage (approx. 12 V nominal) present at module power pin
- Expect stable bus traffic with regular CAN frames when communication is healthy
Diagnostic algorithm
- Use a scan tool to record all active and stored codes and any freeze‑frame data. Note if multiple modules report U codes.
- Verify vehicle battery voltage is healthy and stable. Poor battery can cause network issues.
- Visually inspect connectors and wiring to the tuner/amplifier and HPCM; repair any corrosion, bent pins or damage.
- Check fuses and module power/ground circuits for continuity and correct voltage.
- With key on (engine off), measure CAN_H and CAN_L at the tuner/amplifier and HPCM connectors. Compare to expected idle and dominant voltages.
- Measure termination resistance across CAN_H and CAN_L (engine off). Expect ~60 Ω. If open or very low, address termination or short.
- If CAN voltages or termination are abnormal, trace and repair wiring (short to Vb/ground or open).
- Test the temperature sensor circuit at the tuner/amplifier: measure sensor resistance or voltage signal and compare to spec. If out of range, replace sensor/module.
- Perform a wiggle test of harnesses while monitoring live data/communication to find intermittent faults.
- If wiring and sensor check good, update module software if available and clear codes. Re-scan and road test to confirm repair.
- If communication cannot be restored after electrical checks, consider replacing the failed module (tuner/amplifier or HPCM) following manufacturer procedures.
Likely causes
- Intermittent or corroded connector at the tuner/amplifier or HPCM
- CAN bus wiring fault (open or short between CAN_H and CAN_L or to battery/ground)
- Failed tuner/amplifier temperature sensor or amplifier module
- Loss of power or ground to the HPCM or audio module
Fault status
Status
Temperature sensor signal error reported by tuner/amplifier and/or lost communication with Hybrid Powertrain Control Module on H‑CAN. Indicates a sensor, module, power/ground, or CAN network fault requiring electrical and communication checks.
Repair difficulty: Medium
Diagnostic time: 1.0 - 3.0 hours
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