B2799

Engine Immobiliser System Malfunction

Car Fault Codes Toyota Body

Can you still drive? No, stop right away

Who can fix it? Needs a specialist or dealer

Typical repair time 30 minutes – 4 hours

Typical cost SAR 150 to 5,000

What it means

This is a Toyota-specific code; the same number may mean something else on other makes. The immobiliser checks the transponder chip in the key and then allows the engine computer to run the engine; this code sets because communication between the immobiliser unit and the engine computer is faulty or the ID codes do not match. The result is usually a no-start or an engine that starts and dies after a few seconds.

Models covered: Toyota models with a transponder-key immobiliser (most models since about 1998).

Symptoms4

Engine cranks but will not start, or starts and dies within seconds.
Security light (lock or key symbol) on the dash flashes or stays on.
Sometimes the problem occurs with one key but not another.
The check engine light may come on.

Possible causes6

Damaged key transponder or a key not registered to the car.
Interference from another chip key or electronic cards on the same key ring.
Faulty antenna coil around the ignition switch or its amplifier.
Loose or corroded connectors or broken wiring between the immobiliser unit and the engine computer.
Engine computer or immobiliser unit replaced without registering them together.
Low battery voltage during cranking.

How to diagnose5

Try the spare key, and keep other keys and cards away from the ignition key.
Check the battery and terminals and confirm enough voltage while cranking.
Read immobiliser and engine computer codes with a Toyota-capable scan tool.
Check connectors and wiring between the antenna, immobiliser unit and engine computer.
If the computer or immobiliser unit was replaced recently, confirm the registration procedure was done.

How to fix5

Use a working key and remove sources of interference.
Charge or replace the battery and clean the terminals.
Repair faulty connectors or wiring.
Replace the antenna coil or amplifier if proven faulty.
Register keys or the engine computer at a dealer or qualified programmer, then clear codes and confirm starting with every key.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

Fixing interference, the battery or a connector is simple; key programming or engine computer registration needs dealer-level tools and can exceed the general price table.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions

Why does the engine start and then die after a few seconds?

That is how the immobiliser behaves when it cannot verify the key: it allows a brief start, then cuts fuel or ignition. Try the spare key before anything else.

Can any key shop copy a new key?

Cutting the blade is easy, but the chip must be registered to the car with the right tool. An unregistered key opens the doors but will not run the engine.

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This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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