C1121

Code

HYUNDAI C — Chassis

Front Left Sensor Battery Voltage Low | Sensor 1 Battery Voltage Low

Brand: HYUNDAI

Type: C — Chassis

Views: UK: 11 EN: 23 RU: 11

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Page language: EN

TPMS (wheel) sensor battery depleted or near end-of-life
Damaged or corroded valve stem/sensor assembly
Sensor body or internal electronics failure
Incorrect sensor mounted (wrong frequency/part) or not programmed
Intermittent RF transmission due to wheel/tire interference or wheel weight location
Receiver/antenna/module fault or poor wiring/connectors

Read codes and freeze/frame data with a capable scan tool; confirm code and occurrence count
Use a TPMS/TPMS-activated tool to interrogate the front-left sensor ID and report battery voltage and signal strength
Inspect the front-left wheel valve stem and sensor for physical damage, corrosion or missing cap
Check for recent tire service history (sensor removed/reinstalled) and confirm proper sensor part number
Verify vehicle TPMS frequency (region dependent) and ensure sensor matches
Check receiver/antenna module connections and related wiring for corrosion or damage if other sensors also fail

Typical TPMS sensor supply: single-use coin cell ~3.0 V nominal; low threshold commonly ~2.6–2.8 V (varies by sensor manufacturer)
Common TPMS transmit frequencies: 315 MHz (NA) or 433 MHz (EU/Asia) — vehicle must match sensor frequency
Transmission interval: periodic (during drive) and on valve wake events — scan tool can usually force a wake
Receiver receives tire pressure and temperature CAN or LIN messages at periodic intervals; scan tool may show RSSI/response strength

Connect a diagnostic scan tool and read TPMS/ABS/BCM codes; confirm C1121 and note any other TPMS codes.
Use a TPMS activation tool to read the front-left sensor ID, battery voltage (if available) and RSSI. Attempt to awaken the sensor with the tool and by rotating the wheel slowly.
If the sensor responds and voltage is low, replace the front-left TPMS sensor (recommended to replace at or below manufacturer low-voltage threshold).
If the sensor does not respond, remove tire and inspect sensor and valve stem for damage or corrosion. Replace sensor if physically damaged.
If a new/repaired sensor is fitted, program/learn the sensor ID to the vehicle per Hyundai procedure (manual or automatic relearn).
If replacing sensor does not restore function, inspect TPMS receiver/antenna wiring and connectors; check for related communication DTCs (U0xxx, C11xx).
Clear codes and perform a road test or use an activation tool to confirm normal sensor reporting and that C1121 does not return.
Safety: use proper tire changing equipment and follow safety procedures for handling wheel-mounted sensors and pressurized tires.

End-of-life battery in front-left TPMS sensor (most common)
Damaged/corroded sensor or valve stem from tire service
Sensor not responding because it is the wrong frequency or not learned to the vehicle
Receiver/antenna issue if multiple sensors are affected

⚠️ Status

Front Left (Sensor 1) TPMS transmitter battery voltage low or insufficient transmitter voltage detected.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-1.5 hours

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C1121 — Front Left Sensor Battery Voltage Low | Sensor 1 Battery Voltage Low