Chevy Sonic Code 84 – What Does It Mean? And What to Do?

Chevrolet Sonic is a really legendary vehicle. This is one of the cars that you may not expect a lot from but then you get surprised how good they are on a road and how comfortable they may be. But the model doesn't come without a pinch of salt. It may throw several common codes and make you think a lot about how to diagnose and repair the vehicle.

Code 84 message highlights

• Common reasons:any other code in control units
• How to fix:read the codes and see what triggers the message
• Possible consequences:depends on what initially triggers the message
• Priority level:Medium
• Can you drive?Carefully
• DIY repair:Possible
• Repair price range:$150-$500

Symptoms you should register with Code 84 in the Sonic

The Code 84 is not actually the DTC that you can get out of the ECU. So, it's not possible to tell you right now that it's about, let's say, a crankshaft position sensor failure. No, you can't understand the problem that easily.

And because of this, you will need to pay attention to possible symptoms that accompany Code 84. First of all, the number 84 will illuminate in the bottom right corner of the dash screen in the big box named Code.

Also, your Sonic may experience all kinds of different problems you need to spot:

• check engine soon light illuminating or flashing - this means there is a code in the ECU that needs to be read;
• poor stability control, no ABS, or other braking problems - obviously, the Code 84 comes from braking issues, in this case;
• engine power may or may not be limited depending on the initial reason why you see the Code 84 on the dash of your Sonic;
• engine sensors are giving crazy readings - some sensors may not be working or it may happen because of timing issues;
• there is a problem with misfiring in one or several cylinders and the ECU decided to put the engine in limp mode.

Well, it's not the entire list of things that can trigger the Code 84 problem in your Chevy Sonic. Locating the problem and fixing it sometimes may be pretty complicated. So, if you can't locate any immediate symptoms that accompany the Code 84 on your dash, you should go to a specialist and have the car inspected.

The worst thing you can do is to ignore the issue. Even the smallest problem that now doesn't disturb you from driving the car, may grow into a fatal issue in several hundred miles without you noticing any changes.

What exactly does Code 84 mean?

It's important to understand that this is not the DTC. This is the way for the Sonic to tell you that the engine power is reduced. But it doesn't tell you why. Simultaneously, there may be a DTC in the engine control unit and you should know it by plugging in the scanner. In most cases, this helps you better understand what's happening with your vehicle now.

So, the Code 84 on your dash means the following:

• there is a problem in your vehicle that has something to do with the engine operation;
• the engine power has been reduced to avoid engine damage;
• you can still drive but remember that the engine power is not full now;
• the problem may or may not disappear after you turn the engine off and then on again.

There is a lot of misunderstanding when Code 84 pops up on the dash of the Sonic. A lot of drivers take it for the error code that tells about some actual problem. And you can even find on forums some explanations of what it actually means like a broken sensor in the engine or a faulty ECU, a glitch in software, etc.

But no, it's not a classic error code. This is a warning message telling you that the engine power is reduced but it doesn't explain to you why this happened.

How can you try and solve the problem immediately?

If you are driving on a highway and suddenly see the Code 84 on your dash, you may start panicking. The nearest Chevrolet dealership is hundreds of miles away and you start losing power in your Sonic. There are several things you may try doing.

Here is the most obvious option:

• stop the vehicle in a safe place;
• open the hood and let the engine cool down a little;
• locate the battery of your Sonic;
• disconnect the negative terminal, then disconnect the positive one;
• keep the car disconnected for 5-7 minutes;
• you may press the honk to use all the stored power;
• after that, connect the battery and check if you can start the car;
• start driving and see if the Code 84 error pops up again.

If it doesn't pop up, you just solved the problem temporarily by resetting the ECU and clearing all the codes. But the code may get back to you and you will have Code 84 again, anyway, so, keep watching and drive carefully.

If this doesn't help you solve the issue, you will need to find what exactly triggers the code. If you are in the middle of nowhere and just can't use any equipment or professional help, keep driving slowly and carefully. But plan a visit to the dealership as soon as possible.

What can trigger the Code 84 in your Chevy Sonic?

Actually, anything can trigger this code and I will not dig too deep into this question. I will just give you several examples of what can be the reason for this annoying code illuminating on the dash of your Sonic.

Here they are:

1) Engine problem

If engine sensors detect that the engine has a lot of misfires or the emissions are not OK, you will get the Code 84 and the limp mode.

2) ABS issues

In this case, the ABS light will also be flashing. It very often happens when you drive on a big puddle and the brakes are wet. In this case, just keep driving and the code will disappear after you restart the engine.

3) Oxygen sensor readings

Your emission system is important and if it registers that something is wrong with the rate of harmful emissions, it will trigger the limp mode and Code 84.

4) Software problem

Although the Sonic is not the most up-to-date vehicle in the world, it has several electronic control modules that are packed with software. As you probably know, car software tends to fail sometimes, and resetting with the battery disconnection should help, in this case.

5) Wiring problems

It's not uncommon for a Chevy Sonic to develop some problems with wires and connections, especially if your vehicle is pretty old and has a lot of miles on it.

When should you go for professional help?

If you are not a car mechanic, everything you can do is reset the ECU by disconnecting the battery. But you should understand that this is not a long-lasting solution. It's likely that the Code 84 will come back later and will torture you with slow speed and poor acceleration of the vehicle.

So, it's always recommended to go to the dealership or to a trusted repair shop. These guys will use a good scanner to read the codes from the ECU and will look at the most common problems with the Sonic to locate the initial issue. This will help them find and solve the problem and let you drive the car without having any problems with it.

Can you drive your Sonic with the Code 84 in it?

Actually, yes, you can keep driving. But remember that your Sonic now has much lower power than earlier and it may be the problem for you. One of the most important things is that sometimes the problems may be with the ABS and brakes. And this is the case when you should drive extremely carefully.

When you see the Code 84 in your Sonic, you should know that you may keep driving but there are several things to consider:

• your acceleration will be extremely sluggish and, on the highway, this may be a safety issue;
• the speed of the car will be limited;
• you may lack some functions like the AC or music;
• some other important functions may not work well.

So, it's important to keep driving extremely carefully. It's much better to try disconnecting the battery first to try and solve the issue there and then. Even if you managed to get rid of Code 84, you should plan your visit to the dealership and discuss this with the mechanic.

Final thoughts

Be careful with any error messages or warnings that you don't understand. Code 84 in your Chevy Sonic means that the car lost power due to limp mode and now you need to figure out what exactly happened with the Chevrolet. Otherwise, you will not be able to drive the car because of poor acceleration and codes flashing.

In this article, I've explained what Code 84 means and how you can deal with it. But if you still have questions, just ask them in the comments below.