What To Do When High Exhaust Temp Light Comes On (DEF Temp)

The vehicles that have a diesel engine under the hood have lots of devices to be worried about. These devices all come with their own sensors and warning lights. The key is not to get confused or you may apply a solution that is for another warning light

The source could be due to the fouling of the turbine, which translates into a bad turbocharger performance, which then creates low airflow & charge air pressure which results in high exhaust gas temperatures. The solution for some is to have the DPF cleaned but that does not always work for everyone.

To learn more about this situation, just continue to read our article. It has the information you want to know about so you can handle the problem quickly when it happens to you. You may have to go through a regen to clear the light.

What Does It Mean When The Exhaust Temperature Light Comes On?


This is a little warning that the exhaust temperature is hotter than normal. Then it is telling you to not park anywhere near flammable items. This light can be triggered after an after-treatment regeneration.

What is important to note is this is not a malfunction light. It is an advisory light that reminds you to not park on dry grass or near other combustible items like gas, etc.

The word to handle this situation is that you should keep driving so the regen can go full cycle and clear the lamp for you. The regen usually does not work when you are idling at a light or parked on the side of the road.

If that is not possible, you should take the DOC and the DPF parts to the shop that can clean them for you. Just make sure they clean them as some shops say they do but they may not do a great job at it.

The cost of cleaning is under $500 for both.

Why is My Exhaust Temperature High?

One of the common causes of this problem is a fouled turbocharger. This usually takes place on the turbine side of the turbocharger. So if the turbine is fouled, then the turbocharger can’t perform up to specs.

When that happens you get lower airflow and problems with the charge air pressure. This situation creates a high exhaust gas temperature (EGT). However, there is no set standard for excessive or maximum, or safe EGT range. This boundary is still under debate.

The rule of thumb is for any vehicle not to exceed 1250 degrees F. Nor should you operate any vehicle when the temperature is in the 1200 to 1250 degree F range for extended periods of time.

The average temperature for this aspect of your engine is between 600 to 930 degrees F. It is possible to push this temperature level up to 1600 to 1800 degrees F if you drive for long periods of time. Yet, no one seems to know what is the end of a safe temperature range.

If you have this system in a gas engine, then the cause would be a rich fuel to air mixture. To cure the problem, you have to dial back the turbocharger somewhat to even out that fuel to air mixture somewhat. With diesels, everyone else just points to the turbine side of the turbocharger.

What Happens If The Exhaust Temperature is Too High?


This is an advisory warning light. It does not indicate that there is a malfunction anywhere in your engine systems. What that means is that you can expect your vehicle to stay at full power and not derate.

When the light comes on, you are supposed to park in a safe spot and wait for the regen to complete its cycle. This may or may not be possible as not all regen systems work the same.

Some will have you keep driving as they will not work at idle. Or you can stop and do a forced regen to get the temperature levels down to normal levels. There is nothing catastrophic that will happen that we know of.

Everyone talking about this just says to wait for the regen to be completed and you will be fine. A long with the fact that no one knows where the line is between risky or dangerous EGT levels and safe EGT levels are.

What can happen is if you park in the wrong spot, you could start a fire, cause an explosion, or worse. But now that we have your attention, all that means is not to park over or near anything flammable.

So you avoid parking next to the propane delivery truck. Or stay off grass in the middle of a drought. We have not come across any horror stories or horrific warnings concerning this issue.

You should be 100% safe if you take the right precautions.

What To do When High Exhaust Temp Light Comes On

This is not going to be a situation where you park your truck and then run for your life. This is not like the movies and you are not going to be in a dangerous situation where one wrong move destroys everything within a 500-foot radius.

All you have to do is watch for the regen cycle and after it kicks in keep driving till it is finished. When the cycle is over, the light should go off on its own. Or you can park and do a forced regen to accomplish the same thing.

The key to this situation is to park in a relatively safe spot. By safe we do not mean by the river’s edge or in a completely vacant area. You just have to watch out for flammable objects including trees, brushes, dry brush, and so on.

Also, stay away from gas tanks, propane tanks, and similar flammable items. The EGT is very hot and the heat could cause something to catch on fire or explode.

Again, we have come across zero horror stories where this system has created a fire or caused anything to explode. You are not working with propane or nitro glycerine here. You are working with overly hot exhaust gas that needs to be cooled down.

If you keep things in perspective, then you should be just fine. Find a good spot to park in while you wait. The shadier the better so you do not get too hot either.

High Exhaust Temperature Light John Deere


Normally, the EGT light will only come on when the system is doing a self-regen. It will stay on until the cycle is over and then it will shut the light off. This seems to be the process for all of the EGT lights.

When it comes to John Deer tractors, the regen will come on for about 30 to 45 minutes but it does not interfere with operations. You can do the task you are doing while the regen takes place.

You may hear a weird noise or you may not. It just depends. Some people have frequent EGT lights turning on and off after only a few minutes at a time. This seems to be normal as well as the regen seems to work at around 1500 rpm and not at 2500 rpm.

Some regens only take 30 minutes, others take 45 depending if you are stopped or moving or not. That is the word we got from John Deer tractor owners.

What we want to point out is that nothing out of the ordinary took place. They were able to do their thing while the regen took place. This could be either sitting still or mowing the lawn.

If the light stays off, you may be fine and running at normal EGT levels. According to one manual, do not stop the regen process until it has completed its cycle.

Cummins High Exhaust Temp Light

According to the Cummins engine light identification guide, this is just an advisory light that tells you that exhaust temperatures are higher than normal due to a regen process taking place.

In the driver action side of this document, all it says is to make sure the exhaust pipe is not directed at anything flammable. To be more specific, any combustible surface or material.

It also says that if you smell a foul odor or see a white powder residue, then take the vehicle to the shop and have it inspected for leaks. You can read this guide by clicking this link.

If you are not sure how to do a parked regen, then this guide provides those instructions at the bottom of the guide. Or just read the following instructions:

If the vehicle has a DPF Switch and the DPF Lamp is flashing:

1. Park the vehicle, and set up a safe exhaust area. Confirm that there is nothing on or near the exhaust system surfaces.

2. Set the parking brake, and place the transmission in Park or Neutral.

3. Make sure that your fast-idle and Power Take-Off (PTO) switches are off.

4. Push the DPF Switch into the ON position to start the parked regeneration.

5. Engine speed will increase throughout the duration of regeneration, and exhaust gas and exhaust surface temperatures

will remain higher than normal for three to five minutes after regeneration is complete.

6. Allow up to one hour for the regeneration, and monitor the vehicle and the area around it during the process

That is all there is to do a forced parked regen.

DEF Temperature Light


When you are in an EGT situation, it is the DPF light you should be concerned about. When it is flashing, you need to stop and perform a regen to clear the system.

The first warning will be a solid amber light and you are getting plenty of warning. You may have several hours to go before you need to do the regen. To do a passive or automatic regen, just keep driving at an uninterrupted speed. In other words, do not get off the freeway until it is over.

The second warning will be when this light starts to flash. It is telling you to park your vehicle and start a parked regen asap. Then if you get a check engine light while the DPF light is flashing, it means stop right now and do the parked regen.

We have given you the instructions for the parked in the previous section. Follow those instructions to be successful. This should take between 20 and 40 minutes to do. You may hear a change n the RPM levels during the regen.

The HEST light should come on during this process but it will shut off once the process is done.

What Happens If You do Not do The Parked Regen

You get one last warning before you could cause damage to your engine. There is a third warning light that says stop engine that will come on. If you ignore it you will clog your DPF and cause the aforementioned damage.

After clogging, the DPF will need to be cleaned. This is where you have to be careful as some shops say they have cleaned it but may not have done a great job. You have to be careful as cleaning can cost a lot of money.

You can avoid cleaning if you follow the instructions concerning the forced parked regen. These filters are designed to last 300,000 miles so if you take care of them, it should be a long time before you have to replace them.

Some Final Words

Modern technology has added a lot of responsibilities to the driver of modern engines. There is so much to keep an eye on when you are driving. If you see one of the lights light up, make sure you know what the light is referring to.

You do not want to apply the wrong solution as that can damage your engine. Do not be afraid to ask for help with the meanings. Many discussion forums are very helpful and informative.

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