Affected Component: Immobilizer System / Engine Immobilizer ECU
System: Anti-Theft / Engine Authorization / Security
Severity: High – May prevent engine start entirely
🔍 What Does Toyota Error Code B2799 Mean?
B2799 – Immobilizer System Malfunction indicates that the Engine Control Module (ECM) and the Immobilizer ECU failed to properly communicate or authenticate the key’s identity. This security-related fault typically disables the vehicle’s ability to start until the issue is resolved. It’s one of the most common reasons for “no-start” conditions in Toyota vehicles.
📍 When and Why It Appears
- When a key with a non-programmed transponder chip is used
- After battery replacement or electrical reset (ECU loses sync)
- When the immobilizer antenna or transceiver is faulty
- During or after attempts to reprogram the key or ECM
⚠️ Common Symptoms of B2799
- Engine cranks but does not start
- Security light blinking continuously on dashboard
- No response when turning the key or pressing start (in push-button models)
- Check Engine Light ON (sometimes together with P-code)
🔎 Common Causes
- Unregistered key or defective key transponder
- Faulty Immobilizer ECU or ECM
- Open or short circuit in the transponder coil wiring
- ECU and immobilizer not synchronized (after ECM replacement)
🧰 How to Diagnose Toyota Code B2799
- Use a Toyota Techstream or equivalent scanner to read immobilizer data
- Check key registration status in the immobilizer system menu
- Test the transponder coil for resistance (typically 5–10 ohms)
- Inspect immobilizer antenna ring for cracks or damage
- Verify there’s no moisture or corrosion near the ECU connectors
🔧 How to Fix Toyota Error Code B2799
- Reprogram or register the key using Techstream or dealer service
- Resynchronize the ECM and Immobilizer using immobilizer utility
- Replace faulty transponder coil, antenna, or Immobilizer ECU if needed
- Replace ECM if no communication or sync is possible after diagnostics
💰 Estimated Repair Costs
- Key Programming: ₱800 – ₱2,000
- Transponder/Antenna Coil: ₱1,000 – ₱3,000
- Immobilizer ECU: ₱4,000 – ₱8,000
- ECM Replacement (rare): ₱12,000 – ₱25,000
- Labor: ₱1,000 – ₱2,000
🧠 Expert Tips
- If you recently changed the battery or ECM, re-initialize the immobilizer system immediately
- Have at least two registered keys on hand—Toyota systems often require them for reprogramming
- If your key was cloned or duplicated at a third-party shop, ensure it’s properly coded to your VIN