Vacuum Switching Valve Symptoms – How To Detect A Faulty VSV?

To ensure a vehicle’s engine performance, all components need to function smoothly, from small ones, such as the heater control valve and engine management light, to the main parts of a car, like the hot coolant or the battery. 

Among them, although a vacuum switching valve is a minor part, it plays an important role in securing a workable automobile.

This article is for you if you don’t know what a vacuum switching valve is and its function. We will provide basic information about this component and some faulty vacuum switching valve symptoms

Without further ado, let’s get started.

What Does The Vacuum Switch Valve Do?

The vacuum switching valve (VSV) regulates the vacuum supply to the actuator. It is usually closed and only opens when the electronic control unit energizes it. 

By turning on the VSV and shutting the air control valve, the vacuum is directed to the actuator. This essentially lengthens the air intake manifold. 

In contrast, de-energizing the VSV blocks the vacuum to the actuator, draining the trapped vacuum off the diaphragm.

The VSV determines when the fuel vapor is allowed to escape from the charcoal canister and go into the vacuum. 

When the valve works properly, it will create an audible cracking sound when it opens and shuts. These valves can be controlled by hand, pneumatically, or electrically.

Also, a coolant VSV acts as the heater control valve for many automobiles. It is a basic electrical switch that is opened and closed by a diaphragm vacuum. 

This switch, when triggered, allows antifreeze into the inside of the heater core. This makes the heater work and reduces air temperature.

Since the coolant vacuum switch effectively works as a heater control valve, it can disable the heater core if it malfunctions or has any faults. 

In the long run, the worst-case scenario is that driving with a vacuum leak and elevated temperatures caused by operating a lean air-fuel ratio might lead to broken engines.

That said, the vacuum leaks might stem from a bad valve cover gasket, so check every related part carefully.

What Are Bad Vacuum Switching Valve Symptoms? 

Car engine part
Car engine part

There are some symptoms inside the VSV valve and heater core, such as the heater releasing warm air or not blowing any warm air at all and coolant leaks.

Beside, other signs of a faulty EGR valve you can observe with your eyes are:

  • Your car has a rough idle.
  • The car has increased fuel consumption and decreased fuel efficiency.
  • You can smell fuel.
  • The engine management light stays on.
  • There are more vehicle emissions.
  • There are engine noises when driving, like knocking or tapping.
  • Low engine speeds

A faulty vacuum switch valve can result in many mechanical problems for your car. Thus, knowing the symptoms of a failing VSV could help you notice the issues soon and take actions to deal with them. 

So, scroll down to get more details.

The Heater Blowing Warm Air

The Heater Blowing Warm Air

The very first sign of a failing VSV is a heater that only blasts tepid air as the valve only opens halfway. The flow of hot antifreeze to the heater core will be restricted, reducing the heater’s efficacy.

The Heater Not Blowing Warm Air

One more severe sign to pay attention to is the car heater does not produce any heated air. 

If the VSV malfunctions entirely, no coolant will be able to enter the heater core and create warm air. To this end, the only option to get the heater working again is to change the valve.

Coolant/ Antifreeze Leak

A coolant/antifreeze leak can occur due to a number of factors, including a blown radiator hose, a faulty hose on the intake, a warped head gasket, or, most commonly, EGR valve failure. 

Because the VSV also acts as a heater control valve, it comes into close touch with coolant and is, therefore, vulnerable to leaks. 

The coolant vacuum valve switch is important since it controls the heater and is linked to the car’s cooling system as well.

As a result, if you believe that your VSV is malfunctioning, get the car evaluated by a qualified technician.

How Do You Tell If the Toyota Vacuum Switch Valve Is Bad? 

Vacuum Switching Valve Symptoms

The Toyota vacuum switching valve is a part of the exhaust gas recirculation (EGR) system. If you own a Toyota, this part will be useful as we’ll show you how to test the Toyota VSV valve.

Step 1

The first thing you need to do is to find the location of VSV Toyota. It is equipped with three vacuum hoses and a two-wire electrical hookup. 

The VSV is positioned below the intake gasket at the back of a four-cylinder engine. On six-cylinder engines, you can find the VSV behind the V-Bank cover. 

Step 2

Next, you examine the resistance. You can disconnect the electrical connector and use an ohmmeter to measure the resistance between the terminals. 

The result should be between 33 and 39 ohms under normal conditions. The VSV is having some trouble if the reading is out of this range.

Step 3

The following step is a continuity check. You can use an ohmmeter, ensuring no continuity between the VSV connection and the engine’s electrical ground. Any continuity at either terminal suggests a faulty VSV.

Step 4

We continue with a blowing check. Take the vacuum hoses out of ports E and G. Put air into port E and ensure it exits at port G. If this doesn’t occur, the VSV is defective.

Step 5

Finally, you apply voltage while blowing air. You can use cables from the battery terminals to transmit battery voltage throughout the VSV terminals. 

Pump air to port E and observe what happens in port F. If it fails to do so, the VSV valve Toyota is malfunctioning.

VSV valve Toyota


So we have finished understanding vacuum switching valve symptoms. After reading this post, we hope you have a good grasp of the VSV, its functions, and some signs of a problematic one. 

Our detailed guidelines on testing the VSV for those owing a Toyota could also help you detect the issues sooner.

As this component plays an important role in your car’s engine performance and fuel economy, you should check and maintain it regularly to ensure safety and lasting performance. Thanks for reading.

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