C2122 – Transmitter ID 2 not received (main) (Toyota)

Toyota-specific code — factory diagnostic data

C2122 means the car stopped receiving one of the expected wireless transmitter IDs, so a safety system may not work correctly. On a 2015 Toyota Auris, you will usually notice a tire pressure warning and missing tire data before you notice any drivability change. According to Toyota factory diagnostic data, this code indicates “Transmitter ID 2 not received (main).” That wording matters because it points to a missing identification signal, not a confirmed bad sensor. Your job is to prove whether the transmitter stopped sending, the receiver cannot hear it, or the ECU lost power, ground, or network stability.

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C2122 Quick Answer

C2122 on Toyota means the main receiver/ECU did not receive “Transmitter ID 2.” Confirm which transmitter ID the ECU expects, then verify RF reception, power/grounds, and registration before replacing parts.

What Does C2122 Mean?

Official definition: “Transmitter ID 2 not received (main).” In plain terms, the Toyota chassis system expected to hear from transmitter ID 2 and did not. In practice, the system cannot update that transmitter’s data, so it may flag a warning and disable related monitoring for that position.

What the module actually checks: the ECU compares the list of registered transmitter IDs to incoming RF messages. It expects each registered ID to report within normal operating conditions and timing. When “ID 2” stays absent long enough, the ECU sets C2122. Why that matters: the code identifies a missing message condition, not a failed component. Diagnosis must confirm whether the transmitter stopped broadcasting, the receiver path failed, or the ID registration does not match what the ECU has stored.

Theory of Operation

On Toyota systems that use registered transmitters, the ECU stores multiple unique transmitter IDs. Each transmitter periodically broadcasts its ID and sensor data by radio frequency. The receiver, ECU, or integrated module validates the ID, then updates live data and warning logic.

C2122 sets when the ECU cannot validate messages from the specific stored entry labeled “Transmitter ID 2.” A dead transmitter, incorrect ID registration, or weak reception can cause that loss. Power, ground, or internal faults in the receiver path can also block message decoding. Intermittent faults often show up after tire service, wheel swaps, or low vehicle battery events.

Symptoms

C2122 usually shows up as a warning and missing data for one registered transmitter.

• Scan tool behavior Live data shows no updates for one transmitter ID, or that ID shows “not received” or “no signal.”
• TPMS warning The tire pressure warning light stays on, or flashes then stays on, depending on Toyota logic.
• Missing reading One tire position may show dashes or no pressure display if the vehicle supports individual display.
• Intermittent warning The warning may come and go, especially with temperature changes or longer drives.
• After service The concern appears right after tire rotation, wheel replacement, or sensor registration work.
• Delayed setting The warning may not trigger until several minutes of driving because the ECU waits for expected messages.
• No drivability change The engine and transmission usually operate normally while the chassis warning stays active.

Common Causes

• Transmitter ID 2 not programmed or not registered: The main receiver expects a specific ID, so an unregistered transmitter never matches and the receiver logs “not received.”
• Transmitter battery weak or unstable output: Low battery voltage reduces transmit strength and can prevent the main receiver from decoding ID 2 consistently.
• RF interference or shielding near the vehicle: Aftermarket electronics, window tint metallization, or nearby RF sources can block or distort the signal so the receiver misses ID 2.
• Receiver (main) power or ground voltage drop: A high-resistance feed or ground can let the receiver wake up but fail to process RF messages reliably.
• Open or high resistance in receiver-related wiring/connector pins: Poor terminal tension or corrosion can interrupt receiver operation or its internal communication path.
• Data network issue between the receiver and other chassis modules: If the receiver cannot report or share received IDs due to a network fault, the system may flag the ID as not received.
• Transmitter damaged or incorrect part type for the platform: A wrong-frequency or wrong-spec transmitter can transmit, yet the Toyota receiver cannot decode it as a valid ID 2.
• Receiver (main) internal fault: Internal RF stage or logic faults can prevent decoding one ID, even when other IDs sometimes appear normal.

Diagnosis Steps

Use a scan tool that supports Toyota chassis systems and data list functions. Have a DVOM for voltage-drop testing and a back-probe kit. Keep basic hand tools ready for trim access and connector checks. If available, use a known-good transmitter or an RF test tool. Use service information for connector views and registration procedures.

1. Confirm C2122 with a full vehicle health scan. Record stored, pending, and history codes. Save freeze frame data, especially ignition state, vehicle speed, and battery voltage. Note any related chassis, immobilizer, or network DTCs that share timing with C2122.
2. Before any ECU pin testing, check fuses and power distribution that feed the receiver (main) and any related chassis control modules. Perform a network scan on the scan tool and verify the receiver-related module appears and communicates. If the module does not appear, treat it as a power/ground/network problem first.
3. Verify receiver power and ground under load using voltage-drop testing, not continuity alone. Command any available active test that wakes the receiver, or cycle the ignition to keep it awake. Measure ground drop while the circuit operates and keep it under 0.1V. Measure power-side drop from the fuse output to the module feed while loaded.
4. Inspect the receiver (main) connector and harness routing. Look for water tracks, green corrosion, loose terminals, and pin push-out. Focus on areas that see moisture or interior leaks. Perform a gentle tug test on suspect wires and verify terminal tension with the correct probe size.
5. Check for obvious RF blockers and recent changes. Ask about tint film, dash cams, remote starters, trackers, or audio equipment installs. Temporarily unplug suspicious aftermarket devices and retest. Move the vehicle away from strong RF environments and recheck to rule out localized interference.
6. Use the scan tool data list for transmitter reception status. Look for IDs received, last reception time, or “ID registration” status if available on this Toyota platform. Compare transmitter ID 2 behavior to other transmitter IDs. If the tool supports it, run the ID check utility and watch for intermittent dropouts.
7. Differentiate freeze frame from a technician snapshot. Freeze frame shows conditions when C2122 set. Create a manual snapshot or data recording during a drive or a stationary key-on test. Try to trigger the fault while monitoring reception status, battery voltage, and any module reset indicators.
8. If C2122 remains current, attempt the correct Toyota transmitter ID registration procedure for the Auris platform using service information. Confirm the procedure completes without errors and verify the system stores ID 2. If registration fails, do not replace parts yet. Re-check power/ground drops and connector integrity, then repeat registration.
9. If ID 2 still shows “not received,” isolate the transmitter side. Replace only the transmitter battery if applicable and verify correct orientation and clean contacts. If you have a known-good compatible transmitter, test reception without registering first, if the system supports “signal check.” Then perform registration and confirm the receiver now detects ID 2.
10. When network DTCs exist, diagnose them before replacing transmitters or receivers. Check CAN/LIN integrity using service info for the specific network used. Take any communication-line voltage measurements with ignition ON, because bias voltage only appears when powered. Repair shorts, opens, or termination issues, then recheck C2122.
11. Clear DTCs and confirm the repair. Cycle ignition and re-run the same conditions from freeze frame when possible. Verify the code does not return as pending or confirmed. If Toyota logic treats this as a two-trip fault, complete two similar drive cycles to ensure the module does not re-log C2122.

Professional tip: If the receiver appears on the scan tool but ID 2 never shows in the data list, focus on registration status and transmitter validity first. If the receiver drops off the network or resets during the event, treat it as a power/ground voltage-drop or module feed issue. Snapshot recordings catch intermittent receiver resets that freeze frame will not show.

Possible Fixes

• Correct the transmitter ID registration procedure and confirm the system stores and reports Transmitter ID 2.
• Repair power or ground voltage-drop issues to the receiver (main), including fuse contacts, splices, and ground points.
• Clean, repair, or replace damaged terminals and wiring at the receiver connector after confirming poor tension or corrosion.
• Remove or reroute aftermarket electronics or wiring that creates RF interference, then confirm stable reception.
• Replace the transmitter battery or correct an incorrect transmitter part type after verifying compatibility and poor output.
• Repair network wiring faults that prevent the receiver from communicating reception status to other chassis modules.
• Replace the receiver (main) only after you verify proper power/ground, intact wiring, correct registration, and a known-good transmitter still fails.

Can I Still Drive With C2122?

You can usually drive a 2015 Toyota Auris with C2122, but you should treat it as a chassis safety-system warning. This Toyota manufacturer-specific code means the control module did not receive Transmitter ID 2 (main). On Toyota platforms, that condition often points toward a TPMS transmitter signal or an ID registration issue, not a confirmed failed sensor. Your tires still hold air, but you may lose accurate low-pressure warnings. Adjust driving for conditions and check pressures manually with a gauge. If the TPMS light flashes, stays on, or you suspect an actual leak, stop and inspect the tires and valve stems. Do not ignore a tire issue while you chase an electronic code.

How Serious Is This Code?

C2122 ranges from an inconvenience to a real safety concern, depending on the reason the module stopped receiving the transmitter ID. If the only issue involves an unregistered ID after a tire service, the vehicle drives normally and you only lose the automated warning function. The risk rises when a wheel truly loses pressure and the system cannot alert you. Cold weather, long trips, and high speeds amplify that risk. Treat any TPMS warning as a prompt to verify inflation and tire condition. Also note that Toyota chassis codes can pair with other faults. If you see additional ABS/VSC warnings, diagnose those first because they can change braking stability behavior.

Common Misdiagnoses

Technicians often replace a “bad TPMS sensor” as soon as they read “transmitter not received.” That wastes time and money. C2122 does not prove the transmitter failed. It only tells you the receiver logic did not see ID 2 (main). Common errors include skipping ID registration checks after wheel swaps, ignoring a wrong wheel set frequency, and overlooking a weak sensor battery that drops out only when cold. Many miss simple RF problems, like a damaged valve stem, corrosion at the sensor base, or a wheel installed with an incompatible transmitter type. Avoid guesswork by confirming which IDs the ECU expects, then verify reception with scan data and a proper TPMS trigger tool.

Most Likely Fix

The most frequently confirmed repair direction involves correcting ID management, not replacing parts. After tire rotation, wheel replacement, or seasonal wheel changes, verify the ECU contains the correct transmitter IDs and that the system sits in the correct “main” set. Perform Toyota-approved ID registration and then drive the vehicle under conditions that allow the ECU to relearn and confirm reception. If scan data still shows no reception for ID 2, move to circuit-level checks for the TPMS receiver path and power/ground integrity. Only then consider replacing the specific transmitter that fails to respond to an RF trigger test.

Repair Costs

Repair cost depends on whether the confirmed root cause is wiring, connector condition, a sensor, a module, or the labor needed to diagnose the fault correctly.

Last updated: April 3, 2026

Definition source: Toyota factory description · Autel MaxiSys Ultra & EV. Diagnostic guidance is based on factory-defined fault logic for this code.