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Home / DTC / C164681 — CAN Message Failure - TCU

C164681 — CAN Message Failure - TCU

Detailed page for trouble code C164681.

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Code

C164681

HYUNDAI C — Chassis

CAN Message Failure - TCU

Brand: HYUNDAI
Type: C — Chassis
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Page language: EN

Causes

  • Faulty TCU (internal failure or corrupted software)
  • Open, short, or high-resistance in CAN High/Low wiring or connectors
  • Poor or missing ground or supply voltage to the TCU
  • Damage or corrosion at multi-pin connectors (water intrusion, bent pins)
  • Bus termination fault (missing or incorrect termination resistors)
  • A different module on the CAN bus causing bus-off or flooding the bus

Symptoms

  • Transmission-related faults: limp-home mode, harsh or no shifting
  • Transmission warning lamp or MIL illuminated
  • Scan tool cannot communicate with TCU or shows intermittent response
  • Diagnostic trouble codes present for lost communication
  • Erratic vehicle behavior related to shift logic or inability to engage gears
  • Other modules may report related communication errors

What to check

  • Use a capable scan tool to read freeze frame data and confirm C164681 and any related codes
  • Check battery voltage (should be stable ~12.6 V at rest; >13 V when charging) and inspect charging system
  • Visually inspect TCU connector and wiring harness for damage, corrosion, or bent pins
  • Backprobe TCU power and ground pins to confirm proper supply and good ground
  • Measure CAN High and CAN Low voltages with key ON engine OFF and during communication
  • Measure bus termination resistance between CAN High and CAN Low (~60Ω typically)

Signal parameters

  • CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (key ON, no activity)
  • Dominant state during message: CAN_H ~3.5 V, CAN_L ~1.5 V (differential ~2.0 V)
  • Differential voltage for valid frames: typically up to ~2.0–3.0 V during dominant bits
  • Bus termination resistance: approximately 60 Ω measured between CAN_H and CAN_L (two 120 Ω terminators in parallel)

Diagnostic algorithm

  1. Connect a scan tool and record all communication and transmission-related codes. Note if TCU responds to requests or is missing.
  2. Check battery and charging voltages. Repair charging/battery faults before further diagnosis.
  3. Visually inspect and massage the TCU connector; look for corrosion, water ingress, damaged seals, or bent pins. Repair or replace damaged connectors.
  4. Backprobe the TCU: verify constant and switched power pins, and good ground continuity to chassis. Repair any power/ground issues.
  5. With key ON, measure CAN_H and CAN_L at the TCU connector with a multimeter. Compare to expected idle voltages. If readings are abnormal, proceed to oscilloscope testing.
  6. Measure resistance between CAN_H and CAN_L at two points on the bus to verify termination (~60 Ω). If open or very low, isolate and inspect terminators and wiring.
  7. Use an oscilloscope to view CAN_H and CAN_L waveforms while trying to communicate. Look for missing frames, clipped signals, excessive noise, or a constant dominant state (bus-off condition).
  8. If a module appears to be driving the bus incorrectly, disconnect modules one at a time (starting with the TCU or last-known-changed module) and observe if communication is restored. Replace or repair the faulty module/wiring found.
  9. If wiring and connectors are good and the TCU still fails to communicate, check for available TCU software updates or reprogramming procedures. Follow manufacturer reflash/pairing steps if module is replaced.
  10. After repairs, clear codes, perform a functional test and a test drive while monitoring live CAN/TCU data for stability.

Likely causes

  • Intermittent or failed communication link due to wiring/connectors at TCU
  • TCU lost power or ground causing message absence
  • Another module driving the CAN bus into bus-off or overload
  • Corroded/loose connector pins at the TCU
  • TCU firmware error requiring reprogramming

Fault status

⚠️ Status
CAN message failure detected for Transmission Control Unit — communication lost, intermittent, or invalid messages on the CAN bus involving the TCU.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5 - 4.0 hours

Similar codes

U0100 U0101 U0073 U0105 C1600
371

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