C1107

Code

HYUNDAI C — Chassis

Alternator ‘L’ Over Voltage. | TCS1 message timeout

Brand: HYUNDAI

Type: C — Chassis

Views: UK: 18 EN: 20 RU: 18

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Page language: EN

Faulty alternator voltage regulator (internal overcharging)
Short or high-resistance wiring to/from the alternator L terminal
Faulty battery or battery being charged externally (e.g., improper jump/charger)
Poor ground or battery negative connection
Blown or corroded fuses/ Fusible link related to charging or CAN power
CAN bus wiring fault, loose connector, or module not responding (TCS1)

Battery/charging voltage above normal (bulb-bright headlights, battery swelling)
Battery warning lamp, ABS, TCS or traction control warning lights illuminated
Intermittent or permanent loss of traction/stability control functions
Erratic instrument cluster behavior or communication-related faults
Possible blown electronic components or fuses if over-voltage is severe
Diminished vehicle performance due to disabled stability systems

Read and record all stored DTCs and freeze-frame data with a scan tool
Check key‑on engine-off (KOEO) and engine‑running system voltage with a digital multimeter
Inspect battery terminals, cable condition, and engine/chassis grounds
Inspect alternator connectors (L terminal) and wiring harness for damage/corrosion
Verify fuses and fusible links for charging and CAN/ABS power circuits
Use an oscilloscope to monitor alternator L terminal waveform if available

Key-on, engine-off battery voltage: ~12.4–12.8 V normal
Charging voltage with engine running: ~13.5–14.8 V normal; >15.5–16.0 V is suspicious/over-voltage
Alternator L terminal: should follow regulator control pulse/voltage; steady high voltage indicates fault
TCS1 message frequency: modules commonly transmit 5–20 Hz (check factory spec); missing messages > 0.5–1.0 s may set timeout
CAN bus voltages: CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 1.5–1.8 V idle (verify against service data)

Connect diagnostic scan tool, record DTCs and freeze-frame/graph live data for charging voltage and TCS status.
Visually inspect battery, cables, ground straps, alternator connector and L terminal for looseness, corrosion, or damage.
With a good multimeter, measure battery voltage KOEO and with engine running at idle and at ~2000 rpm; note any voltage above ~15 V.
If over-voltage is present, isolate alternator: disconnect alternator output (per service manual) or remove regulator control and re-measure to confirm alternator source.
If alternator suspected, bench-test alternator or swap with known-good unit to confirm regulator failure before replacement.
Inspect/replace any blown fuses or fusible links found during inspection. Repair wiring shorts between L terminal and B+ if present.
For TCS1 timeout: use scan tool to monitor CAN messages, check continuity and resistance of CAN_H and CAN_L between ECM, ABS/TCS, and other modules; repair any damaged wiring or connectors.
If CAN communications are restored but code persists, reflash or update module software per Hyundai service instructions, or replace faulty control module if necessary.
After repairs, clear codes, perform battery/charging system re-check and road test to confirm no reoccurrence of C1107 and verify TCS/ABS operation.

Internal regulator in alternator failing and allowing excessive voltage at L terminal
L terminal shorted to B+ or another high-voltage circuit
High system voltage measured intermittently due to loose battery ground
Intermittent CAN high/low line interruption causing TCS1 message timeout
Connector corrosion at alternator or ABS/TCS module causing intermittent signals

⚠️ Status

Alternator L terminal over-voltage detected and/or TCS1 communication timeout (loss of TCS1 messages).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

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