C1921 – Tire ID Reception Failed – Tire 2

The Mitsubishi fault code C1921 – Tyre ID Reception Failed (Tyre 2) is a manufacturer-specific diagnostic trouble code stored by the TPMS (Tyre Pressure Monitoring System) ECU — also referred to on some Mitsubishi platforms as the W/C (Wheel Control) ECU. It indicates that the TPMS ECU has lost communication with the radio frequency pressure sensor assigned to the Tyre 2 position and has failed to receive a valid sensor ID transmission within the expected interval. On the standard Mitsubishi four-wheel TPMS numbering layout, Tyre 2 corresponds to the front right wheel. C1921 is a sensor communication fault — the TPMS ECU cannot confirm the pressure status of the front right tyre at all while this code is active — and the TPMS warning light will be continuously illuminated.

What Does C1921 Mean on a Mitsubishi?

Each wheel on a Mitsubishi vehicle equipped with a direct TPMS system carries a battery-powered radio frequency sensor mounted inside the rim on the valve stem. Each sensor periodically broadcasts a data packet containing its unique ID, current tyre pressure, temperature, and battery status to the TPMS ECU. The ECU cross-references every received sensor ID against the four IDs stored in its memory for each wheel position. C1921 is stored when the TPMS ECU fails to receive a valid transmission from the sensor registered to the Tyre 2 (front right) position for a defined timeout period — typically after several consecutive missed transmission intervals. This can result from a dead or dying sensor battery, a physically damaged or failed sensor, a sensor that is unregistered or incorrectly registered to the ECU following a wheel rotation or swap, RF signal interference, or a fault in the TPMS receiving antenna or its wiring circuit serving the front right wheel position.

Symptoms of C1921

C1921 presents with the following indicators:

• TPMS warning light continuously illuminated on the instrument cluster
• C1921 stored in the TPMS ECU when scanned with MUT-III or a compatible scanner
• No live pressure data displayed for Tyre 2 (front right) in the TPMS live data screen — position shown as absent, unknown, or dashes
• Front right tyre pressure status unknown — the TPMS system cannot monitor or alert for low pressure on this wheel while C1921 is active
• No driveability symptoms in most cases — C1921 is a TPMS communication fault only
• Other TPMS positions continue to report normally if only C1921 is stored
• Potential roadworthiness failure in markets where a permanently illuminated TPMS warning light is a testable item at inspection

Common Causes of C1921

• Dead or end-of-life TPMS sensor battery — the most common cause of C1921; most OEM TPMS sensor batteries last 7–10 years and are not separately replaceable — the full sensor must be replaced when the battery is exhausted
• Failed TPMS sensor — internal electronics fault — the sensor circuit board has failed due to age, impact damage, or corrosion, preventing any RF transmission even with sufficient battery voltage
• Sensor not registered to the TPMS ECU following a wheel rotation or swap — the most common non-hardware cause of C1921; a tyre rotation or wheel change without TPMS relearn leaves the ECU holding a stale sensor ID that no longer matches the sensor physically in the Tyre 2 position
• Physical sensor damage from a kerb strike, pothole, or tyre fitting machine contact — impact to the valve stem or sensor body can fracture the internal antenna or circuit board, stopping transmission
• Corroded TPMS metal valve stem compromising the sensor body — severe electrochemical corrosion between the aluminium sensor body and the steel or alloy rim, or corrosion of the valve stem itself, can damage the sensor’s internal components over time
• Wheel fitted without a TPMS sensor — a spare wheel, winter wheel, or aftermarket wheel installed in the front right position without a compatible TPMS sensor will generate C1921 immediately
• TPMS antenna or receiver circuit fault — damage to the TPMS receiving antenna serving the front right position, or a wiring fault between that antenna and the TPMS ECU, prevents reception of any sensor transmission from this wheel regardless of sensor condition
• Temporary RF signal interference — a rare cause; strong nearby RF sources can intermittently suppress sensor reception, though persistent C1921 is unlikely to be caused by interference alone

Common Misdiagnoses

• Replacement sensor fitted without TPMS relearn — C1921 returns immediately: A new TPMS sensor carries a unique ID the TPMS ECU has never seen. Fitting the sensor alone does not resolve C1921 — the new sensor ID must be registered to the Tyre 2 position using a TPMS relearn tool or MUT-III before the fault will clear.
• Sensor condemned without attempting to wake it first: Some TPMS sensors enter a deep sleep or storage mode during prolonged inactivity or very cold conditions. A TPMS activation tool held at the front right valve stem may successfully wake and read the sensor, confirming it is alive before any replacement is ordered.
• TPMS ECU replaced without testing the antenna circuit: If C1921 is caused by a faulty antenna or wiring fault between the antenna and the ECU, replacing the TPMS ECU will not resolve the fault. Antenna circuit testing must precede any ECU replacement decision.
• C1921 assumed to mean the front right tyre pressure is acceptable: C1921 means the pressure is unknown, not satisfactory. The front right tyre pressure must always be physically verified with a calibrated gauge when C1921 is active — a failing sensor may have stopped transmitting while the tyre was simultaneously losing pressure.
• Wheel rotation performed without relearn attributed to sensor failure: After a tyre rotation without relearn, the sensor now in the front right position transmits an ID the ECU does not recognise for Tyre 2, generating C1921. This is resolved by relearn alone — no parts replacement is necessary.

Affected Mitsubishi Vehicles

Model	Generation	Notes	Years
Outlander PHEV	GG/GF (1st Gen)	Direct TPMS standard; Tyre 2 = front right; sensor battery life 7–10 years	2013–2021
Outlander PHEV	GN (2nd Gen)	Revised TPMS architecture; same C1921 definition and wheel numbering	2022–present
Outlander (non-PHEV)	GF/GG/ZJ/ZK/ZL	Direct TPMS market-dependent — verify fitment before diagnosing	2007–present
Eclipse Cross	GK/GL	Direct TPMS standard on most market variants	2017–present
ASX / RVR	GA/XD	Direct TPMS on later variants; confirm system type before diagnosing C1921	2010–present
Galant Fortis / Lancer	CY/CZ	Market-specific TPMS fitment — verify direct vs indirect before diagnosing	2007–2017

Tools & Equipment Required

Tool	Purpose	Notes
Mitsubishi MUT-III / MUT-IV	TPMS ECU scan, live sensor data, sensor relearn, code clear	Required to confirm C1921, view registered sensor IDs, perform relearn, and clear after repair
TPMS activation / relearn tool	Wake and read sensor ID at each wheel; trigger relearn procedure	Required to confirm whether the front right sensor is transmitting and to register a replacement sensor
Calibrated tyre pressure gauge	Physically verify front right tyre pressure while C1921 is active	Always the first step — TPMS cannot monitor pressure on Tyre 2 while C1921 is present
Digital multimeter (DMM)	TPMS antenna circuit continuity and voltage testing	For antenna wiring diagnosis if sensor and relearn are confirmed good
Wiring diagram (OEM)	TPMS antenna circuit routing and ECU connector pinout	Mitchell1 DIY or Mitsubishi FAST-II
Tyre fitting machine	Tyre removal for sensor access and replacement	Required for sensor replacement — TPMS sensors are mounted inside the rim on the valve stem

Step-by-Step Diagnosis

• 1
  Physically Check the Front Right Tyre PressureBefore scanning or testing any component, check the front right tyre pressure with a calibrated gauge and compare it against the vehicle placard pressure on the driver’s door jamb or fuel filler flap. C1921 means the TPMS system is not monitoring this tyre — never assume the pressure is acceptable. Inflate to the correct placard pressure if required before proceeding with TPMS diagnosis.
• 2
  Confirm C1921 and Review Live TPMS Data with MUT-IIIConnect MUT-III or equivalent and read all TPMS codes. Confirm C1921 is current and note whether any other TPMS reception failure codes are stored simultaneously. View the TPMS live data screen and confirm the Tyre 2 position shows no data — pressure and temperature fields absent or dashes. Note the sensor IDs currently registered to all four positions for cross-referencing.
• 3
  Attempt to Wake and Read the Front Right Sensor with a TPMS ToolHold a TPMS activation tool at the front right wheel, positioned close to the valve stem. Activate the tool to send the low-frequency wake signal. If the sensor responds, the tool will display its ID, pressure, temperature, and battery status. A successful read confirms the sensor is alive — the fault may be a registration mismatch or an intermittent battery condition rather than a fully failed sensor.
• 4
  Compare the Sensor ID Against the TPMS ECU Registration for Tyre 2If the TPMS tool reads a sensor ID at the front right wheel, compare it against the ID the TPMS ECU has registered for the Tyre 2 position. A mismatch confirms a registration fault — most commonly caused by a wheel rotation or swap without relearn. A matching ID with the ECU still not receiving the sensor’s transmission in normal driving indicates a failing sensor, a weak battery near end of life, or a vehicle-side antenna fault.
• 5
  Check TPMS Sensor Battery StatusIf the TPMS tool successfully reads the front right sensor and the ID matches the ECU registration, note the battery status reported by the tool. A low battery warning indicates the sensor is near the end of its service life and will soon fail to transmit reliably. A sensor with a critically low battery should be replaced proactively — intermittent transmission from a dying battery often precedes a permanent C1921.
• 6
  Test the TPMS Antenna Circuit if the Sensor is Confirmed GoodIf the TPMS tool reads the front right sensor correctly, the battery is adequate, and the sensor ID matches the ECU registration, but C1921 persists, the fault lies in the vehicle’s receiving circuit. Using a DMM and the OEM wiring diagram, check continuity and supply voltage at the TPMS antenna connector for the front right position and between the antenna and the TPMS ECU connector. A damaged antenna cable, corroded connector, or open circuit will prevent the ECU from receiving the sensor’s RF transmission regardless of sensor condition.

Scanner Readout Explained

====================================================
  MITSUBISHI MUT-III SE — DIAGNOSTIC REPORT
====================================================
  Vehicle:     2017 Outlander PHEV (GG3W)
  Date:        2025-03-27  13:22:41
====================================================
MODULE: TPMS / W-C ECU
----------------------------------------------------
  C1921  Tyre ID Reception Failed — Tyre 2 (Front Right)
         Status:       Confirmed / Current
         Freeze Frame:
           Tyre 2 Sensor ID (Registered):  0x3C8E1A2F
           Tyre 2 Last Received Signal:    >60 min ago
           Tyre 2 Pressure Status:         UNKNOWN
           TPMS Warning Lamp:             ON
====================================================
  LIVE DATA (TPMS Sensor Status — All Wheels)
====================================================
  Tyre 1 (Front Left):    2.4 bar  |  21°C   |  Sensor OK
  Tyre 2 (Front Right):   --- bar  |  ---°C  |  NO SIGNAL — C1921 ACTIVE
  Tyre 3 (Rear Left):     2.4 bar  |  21°C   |  Sensor OK
  Tyre 4 (Rear Right):    2.4 bar  |  22°C   |  Sensor OK
====================================================
  NOTE: Registered ID for Tyre 2 not
  responding. Pressure status unknown.
  Physical pressure check required.
====================================================

Step-by-Step Repair Guide

Repair Path A: TPMS Sensor Relearn After Wheel Rotation or Swap

• 1
  Read All Four Sensor IDs at Their Current Physical Wheel PositionsUsing a TPMS activation tool, read the sensor ID at each wheel in sequence — front left, front right, rear left, rear right. Record all four sensor IDs alongside their current physical wheel positions. This provides the correct registration map that must be programmed into the TPMS ECU to match the post-rotation layout.
• 2
  Perform TPMS Sensor Relearn via MUT-III or Relearn ToolUsing MUT-III or a compatible TPMS relearn tool, initiate the TPMS sensor registration procedure. Register each sensor ID to its correct wheel position — Tyre 1 (front left), Tyre 2 (front right), Tyre 3 (rear left), Tyre 4 (rear right) — using the IDs read at each physical position in the previous step. Confirm all four positions are accepted by the ECU before exiting the procedure.
• 3
  Clear C1921 and VerifyClear C1921 with MUT-III and drive the vehicle above 25 km/h for a short distance to allow all sensors to transmit updated data to the ECU at their newly registered positions. Confirm the TPMS warning light extinguishes and that live data shows valid pressure readings for all four tyre positions including Tyre 2.

Repair Path B: TPMS Sensor Replacement

• 1
  Remove the Front Right Wheel and TyreRemove the front right wheel and bring it to a tyre fitting machine. Break the tyre bead carefully on the valve stem side — the TPMS sensor is mounted on the valve stem inside the rim and must not be contacted by tyre levers or the bead breaker arm. Always inform the tyre fitter that a TPMS sensor is fitted before any tyre machine work begins.
• 2
  Remove the Failed Sensor and Fit the OEM ReplacementFully deflate the tyre. Unscrew the TPMS sensor valve stem nut from outside the rim and withdraw the old sensor from inside the rim. Fit the new OEM or OEM-compatible sensor — insert from inside the rim, fit a new grommet and nut, and torque the nut to the workshop manual specification. Do not overtighten — the sensor body can crack if the nut is over-torqued against the rim seat.
• 3
  Refit the Tyre and Inflate to Placard PressureRefit the tyre to the rim using correct bead lubricant. Inflate to seat both bead lips fully, then adjust to the vehicle placard pressure. Refit the wheel to the vehicle and torque the wheel bolts to the workshop manual specification.
• 4
  Register the New Sensor ID to the Tyre 2 PositionUse a TPMS activation tool to read the new sensor ID at the front right wheel. Using MUT-III or a TPMS relearn tool, register the new sensor ID to the Tyre 2 position in the TPMS ECU. This step is mandatory — without relearn, the ECU will not recognise the new sensor and C1921 will return immediately after fitting.
• 5
  Clear C1921 and Verify All Four Sensor PositionsClear C1921 with MUT-III and drive above 25 km/h to allow the new sensor to transmit to the ECU. Confirm the TPMS warning light extinguishes and that live data shows valid pressure and sensor data for all four tyre positions. Verify the new sensor ID is correctly associated with the Tyre 2 position in the TPMS live data screen.

Repair Path C: TPMS Antenna Circuit Repair

• 1
  Locate the TPMS Antenna for the Front Right PositionUsing the OEM wiring diagram, identify the location of the TPMS receiving antenna serving the front right wheel position. On most Mitsubishi models this antenna is routed in the front wheel arch area or along the front subframe. Inspect the antenna body, its connector, and the full wiring run back to the TPMS ECU for physical damage, chafing, or corrosion.
• 2
  Test Antenna Circuit Continuity and Supply VoltageUsing a DMM and the OEM wiring diagram, check continuity of all antenna feed wires between the antenna connector and the TPMS ECU connector. Verify supply voltage at the antenna is within specification with the ignition on. An open circuit, ground short, or absent supply voltage in the antenna wiring will prevent the ECU from receiving any sensor transmission from the front right wheel position regardless of sensor condition or registration status.
• 3
  Repair or Replace the Antenna and Clear C1921Repair any identified wiring fault using standard automotive harness repair techniques, or replace the antenna assembly if the antenna element itself is confirmed damaged. Clear C1921 with MUT-III, drive above 25 km/h, and confirm live data shows valid pressure and sensor data for Tyre 2 with the TPMS warning light extinguished.

Repair Cost Estimates

Repair	Parts Cost (est.)	Labour (est.)	Total (est.)	DIY Difficulty
TPMS sensor relearn only — no new parts	€0	0.25–0.5 hr	€0–€50	Easy — requires TPMS relearn tool or MUT-III
TPMS sensor replacement (OEM)	€40–€120	0.5–1 hr	€70–€200	Medium — tyre removal and relearn required
TPMS sensor replacement (aftermarket compatible)	€20–€60	0.5–1 hr	€50–€140	Medium — confirm compatibility before fitting
TPMS antenna wiring repair	€5–€30	0.5–2 hr	€30–€180	Medium — requires DMM and OEM wiring diagram
TPMS antenna replacement	€20–€80	0.5–1 hr	€50–€150	Medium
TPMS ECU replacement (if confirmed faulty)	€150–€400	1–2 hr	€200–€500	Hard — relearn of all four sensors required after replacement

Prevention & Maintenance Tips

• Always perform a TPMS sensor relearn after every wheel rotation, tyre change, or wheel swap — the single most preventable cause of C1921 is omitting the relearn step after moving wheels to new positions
• Replace all four TPMS sensors proactively when any one sensor reaches end of battery life — if one sensor battery has failed after 7–10 years, the remaining three are approaching the same point; replacing all four at the same tyre change avoids repeat reception failure codes across different positions in quick succession
• Always replace TPMS valve stem grommets and nuts when sensors are removed for any reason — reused grommets are a leading cause of valve stem air leaks following sensor reinstallation
• Inform tyre fitting technicians that TPMS sensors are fitted before any bead breaker or tyre lever work begins — physical contact from tyre machine equipment is a common cause of sensor damage during routine tyre changes
• Check all four tyre pressures monthly with a calibrated gauge even when the TPMS is functioning correctly — TPMS only alerts at approximately 25% below the recommended pressure; a tyre can be meaningfully under-inflated for weeks before a pressure code appears
• Use only OEM or verified-compatible aftermarket TPMS sensors — sensors with incorrect RF frequencies or incompatible communication protocols will not be recognised by the Mitsubishi TPMS ECU regardless of physical fitment

Frequently Asked Questions

Can I drive my Mitsubishi with C1921 stored?

The vehicle is driveable, but the TPMS cannot monitor or alert for low pressure on the front right tyre while C1921 is active. Before driving, always physically check the front right tyre pressure with a calibrated gauge. If the pressure is correct the vehicle can be driven normally while the fault is investigated — but any subsequent pressure loss in the front right tyre will go completely undetected by the TPMS until the fault is resolved.

C1921 appeared immediately after my tyres were rotated — is the sensor broken?

Almost certainly not. A tyre rotation moves each sensor to a new wheel position, but the TPMS ECU retains the old position assignments until a relearn is performed. The sensor now physically in the front right position transmits an ID the ECU does not recognise for Tyre 2, generating C1921. The repair is a TPMS sensor relearn to update all four position assignments — no parts are required and the existing sensors are not faulty.

Will C1921 clear itself after driving?

Not if the sensor is genuinely failed, dead, or unregistered. A sensor in temporary sleep mode may resume transmitting after the vehicle has been driven for some time, in which case the TPMS warning light may extinguish spontaneously. However, C1921 will remain stored in TPMS ECU memory regardless of whether the warning light clears on its own, and requires active clearing with MUT-III or a compatible scanner.

How do I distinguish between a dead sensor battery and a fully failed sensor?

A TPMS activation tool sends a low-frequency magnetic wake signal to the sensor. A sensor with any remaining charge will respond to this wake signal and transmit its ID and battery status. If the tool receives no response after multiple close-range attempts at the valve stem, the battery is exhausted or the sensor electronics have failed internally — either way, sensor replacement is required. A sensor that responds to the activation tool but reports a low or critical battery status should be replaced proactively.

Do I need to replace all four sensors if only the front right has failed?

Only the failed Tyre 2 sensor is required to be replaced to resolve C1921. However, if the vehicle is 8–10 years old and the sensors are all original, the remaining three are at a similar stage of battery life. Replacing all four at the same time avoids the cost and inconvenience of returning for individual sensor replacements within a short period as the others fail in succession. The decision is pragmatic and depends on vehicle age and remaining expected ownership.

Can I use tyre sealant foam as a temporary fix while waiting to replace the TPMS sensor?

No. Foam tyre sealant should never be used on TPMS-equipped vehicles. The sealant enters and blocks the pressure sensing port of the TPMS sensor, causing permanent sensor damage — meaning a sensor replacement will be required in addition to any tyre repair. If the front right tyre needs a temporary roadside fix, use a tyre plug rather than foam sealant, and have the tyre properly repaired or replaced as soon as possible.

What happens if I fit a new sensor but forget to do the relearn?

C1921 returns immediately. The new sensor has a unique ID the TPMS ECU has not seen before — it is not automatically accepted as the Tyre 2 sensor. The ECU continues looking for the old registered Tyre 2 sensor ID and finds nothing, storing C1921 again. The relearn procedure is always mandatory after any sensor replacement, wheel rotation, or wheel swap — without exception.

Could a winter wheel set cause C1921 if the winter wheels have their own sensors?

Yes, if the winter wheel sensors have not been registered to the TPMS ECU. A second set of wheels with their own TPMS sensors requires a full relearn each time the wheels are swapped between summer and winter fitment. Many tyre retailers offer seasonal TPMS relearn as part of a wheel swap service. Storing the sensor IDs for both sets in the TPMS ECU memory — if the system supports this — simplifies the seasonal changeover significantly.

Conclusion

Mitsubishi C1921 – Tyre ID Reception Failed (Tyre 2 / Front Right) is a TPMS communication fault indicating the ECU has lost contact with the sensor registered to the front right wheel position. The most common causes are a dead sensor battery, a physically failed sensor, or a missing TPMS relearn following a wheel rotation or swap. Always physically check the front right tyre pressure first, attempt to wake the sensor with a TPMS tool, identify whether the fault is a registration mismatch, a failed sensor, or an antenna wiring issue, and always perform a full TPMS relearn after any sensor replacement or wheel position change before clearing C1921 with MUT-III.