Fault code B2799 – engine immobiliser system malfunction

Fault code B2799 may apply to Toyota brand vehicles as well as vehicles manufactured under the GM brand. Depending on your vehicle brand, this fault will have completely different definitions.

The B2799 fault for Toyota brand vehicles sounds like “Engine Immobiliser System Malfunction”. For GM vehicles, the error sounds like “Suspension control select switch circuit open”.

Technical description and explained code B2799

Because this code has completely different definitions, and they refer to different problems in GM and Toyota vehicles. To avoid confusion, each description will be separated by the appropriate headings to provide more understandable information.

Description for Toyota vehicles

The OBD-II trouble code B2799 is defined by the Toyota automaker as “engine immobilizer system malfunction”. It is set when the transmission control module detects a fault or communication error between itself and the transponder key.

This code can also be set when one or more of the control modules involved detect that incorrect security codes are being transmitted from the key to the control module or immobilizer.

Modern anti-theft security systems are very complex, which depend on the transmission and reception of large security code streams. In practice, the key, immobilizer control module and PCM contain the same codes in the same configuration.

In some Toyota vehicles, the same codes are programmed into the central locking system. This means that only the correct key can remotely lock/unlock the vehicle with the key fob.

If all preprogrammed security codes and other information identifying the vehicle. contained in the key, the RCM and the immobilizer control module do not match exactly, the immobilizer will not allow the engine to start.

However, in some cases the engine may start but will be stopped by the immobilizer after about two seconds.

Decoding for GM cars

The General Motors manufacturer’s B2799 error is defined as a “suspension control selection switch circuit failure.” It is set when the body control module detects a fault or defect in the suspension control switch. It may also affect the wiring associated with the suspension control system.

In systems that use manual suspension control, the driver can choose between two levels of damping. Selecting a particular level involves a switch that energizes the solenoids inside the shock absorbers.

Conventional shock absorbers work on the principle of fluid resistance, which involves passing oil through a small hole in the piston of the shock absorber as it moves. If the movement is slow, the oil flows easily through the hole. But at higher speeds, the oil can only pass through the bore at a rate dictated by the viscosity of the oil.

If the car has a suspension control selection, the diameter of the bore in the shock absorber piston can be adjusted by means of an electromagnet. Therefore, the oil flow rate through the piston can be adjusted according to the current driving conditions.

When the PCM detects a B2799 fault in the suspension control system, it sets this code, which causes the warning lamp to illuminate.

Symptoms of vehicle malfunctions Toyota

The main symptom of error B2799 for the driver is the MIL (malfunction indicator) light. It is also called Check engine or simply “check engine light”.

They can also manifest as:

1. The check engine light on the control panel will come on (the code will be written in the PCM memory as a malfunction).
2. The engine may crank but not start.
3. There will almost certainly be no fuel pressure because the immobilizer has disabled the fuel system.
4. The engine may start, but will almost immediately stall again.

Symptoms of a General Motors malfunction

The main symptom of error B2799 for the driver is the MIL (malfunction indicator light). It is also called Check engine or simply “check engine light”.

They can also manifest as:

1. Check engine light on the control panel (the code will be written in the PCM memory as a malfunction).
2. Unable to select the damper damping level.
3. Ride quality may not match the current driving conditions, depending on which mode the system is stuck in.

Causes of the error on Toyota vehicles

Code B2799 may indicate that one or more of the following problems have occurred:

• Damaged or faulty transponder key.
• Damaged or faulty transponder key amplifier.
• Damaged, burned, shorted, disconnected or corroded wiring or connectors anywhere on the alarm/anti-theft system.
• Low system voltage caused by a faulty or discharged battery.
• Malfunction or failure of PCM, or immobilizer control module. (Please note that failure of immobilizer module is more common than failure of PCM).
• Causes of the error on GM vehicles

Causes of the error on GM vehicles

Code B2799 may indicate that one or more of the following problems have occurred:

• Damaged, burned, shorted, disconnected or corroded wiring or connectors anywhere in the suspension control system.
• Blown fuses or fusible links.
• Defective control solenoid.
• Defective shock absorber.
• Problem with control switch.
• Failure of PCM or BCM, failure of which occurs more frequently.

How to fix or reset OBD-2 code B2799

Some suggested steps for troubleshooting and fix the error code B2799 on Toyota:

1. Check the transponder key as well as its amplifier for malfunction.
2. Visually inspect the electrical wires and connectors pertaining to the alarm/ anti-theft system.
3. If necessary, repair or replace any shorted, broken, damaged or corroded components.
4. Check the battery charge.
5. If the problem persists, check and, if necessary, replace the engine control module or immobilizer control module.

Some suggested steps for troubleshooting and fix the error code B2799 on GM:

1. Visually inspect the electrical wiring and connectors pertaining to the alarm/ anti-theft system.
2. If necessary, repair or replace any components that are shorted, broken, damaged or corroded.
3. Do the same with fuses or fusible links.
4. Check that the shock absorber, control solenoid and switch are in good working order.
5. If problem persists, check and replace PCM or BCM if necessary.

Diagnose and repair of problems

The first step in the B2799 troubleshooting process is to review the Technical Service Bulletins (TSB). For known problems with a particular vehicle.

The advanced diagnostic steps are very vehicle specific. It may require, special equipment and knowledge to accurately perform the steps.

On Toyota vehicles, of the simple ones, you can check the battery charge and visually check for breaks or other damage to the wiring. As for checking the transponder key, as well as control modules, it is better to entrust them to professionals. This may require the necessary knowledge and special equipment.

As for General Motors cars, we can also check the wiring and fuses. The rest is better entrusted to professionals, who will quickly figure out if there is a problem with the control module or with the shock absorber.

On which vehicles does this problem occur most frequently

Fault code B2799 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

• Lexus (IS250, RX330)
• Peugeot (107)
• Toyota (Avensis, Camry, Corolla, Crown, Highlander, RAV4, Tundra)

Fault code B2799 can sometimes be found with other errors. The most common are the following: B1703, B2796.

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