Toyota Rav4 Check Engine Light Vsc and 4wd On

Many of the warning lights on the instrument panel light up and then go off every time you start your RAV4. This is part of a self-check to ensure that certain essential lights are working correctly.

But what if some of these lights fail to turn off? What should you do if some of these lights illuminate while you’re on the road? Of course, if the oil pressure or A/T Temp lights come on, you should pull over immediately to avoid any more damage.

However, in the scenario of Toyota Rav4 Check Engine Light Vsc and 4wd ON so why do all these lights come on at the same time and what do they mean? Let’s take a look.

Possible Reason For Toyota Rav4 Check Engine Light Vsc and 4wd ON

Many of these features depend on the engine running at peak performance. The VSC for example uses not only the braking system but also controls the throttle to help get the RAV out of tricky situations. If the engine is not running right, the ECM shuts down those systems that would be affected.

It could be any of a hundred different things such as:

  • A bad spark plug
  • Coil causing a misfire to a bad oxygen (O2) sensor
  • A loose gas cap.

Most of the time Toyota Rav4 Check Engine Light Vsc and 4wd ON Due To:

Loose vacuum hose:


  • Rough Idle: This is mainly because the throttle body is trying to hold a stable idle by opening and closing the throttle valve. If you have a major vacuum leak, the throttle body will have a problem trying to control it, resulting in strange idle symptoms.
  • High Idle RPM: If you have a vacuum leak, it will allow more air to enter the engine – allowing it to rev up.
  • Rough/Slow Acceleration: A vacuum leak will often result in rough or slow acceleration because the engine will get the wrong air/fuel ratio when uncalculated air is entering or leaving the engine.
  • Check Engine Light: Check Engine Light of Vsc and 4wd on.
  • Misfires & Backfires: It will also often result in misfire trouble codes, like the P0300 trouble code. When your car is misfiring on one specific engine, it is usually caused by a vacuum leak around the intake manifold gasket.
  • High pitch noise from the engine: Broken vacuum hoses can often result in a high pitch noises because the engine is sucking air all the time through the leak, which will create noises.

Cause of a Vacuum Leak?

  • Broken Vacuum Hose
  • Intake Manifold Gasket
  • Throttle body gasket
  • Faulty throttle body
  • Cracked intake manifold
  • Leaking solenoids or sensors
  • Cracked or damaged Brake booster
  • Faulty PCV Valve

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2nd The Most Reason For Vsc and 4wd Check Light ON.

Faulty Mass Airflow Sensor


A faulty mass airflow sensor will cause problems similar to low compression or low vacuum, and will also show symptoms similar to when your vehicle has low fuel pressure from a faulty fuel pump. Here are some of the most common symptoms of a faulty mass airflow sensor:

  • The engine is very hard to start or turn over
  • The engine stalls shortly after starting
  • The engine hesitates or drags while under load or idle
  • Hesitation and jerking during acceleration
  • The engine hiccups
  • Excessively rich or lean idling

How To Fix Faulty Mass Airflow Sensor?

If you suspect your vehicle has a malfunctioning mass airflow sensor, take it to a skilled mechanic for a full computer diagnostic. A defective mass flow sensor will generally output a specific code during computer diagnostics, and this code is usually straightforward to detect using computer testing equipment.

About The Author

Avatar for Ibrar Ayyub

Ibrar Ayyub

I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.

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