Wednesday, February 8, 2023


EPA speaks out on failed DEF heads, promises relief – but when?

By Russ and Tiña De Maris
This morning (September 1, 2021), the U.S. Environmental Agency released a formal statement on DEF sensor issues. As we mentioned last weekend, our gut feeling is that the cries of complaint made to both industry and the EPA have pushed the matter over the edge. The EPA speaks out in this statement.

“EPA and the California Air Resources Board (CARB) have been working with the manufacturers of diesel vehicles and engines to address an issue related to the ongoing shortage of computer chips and the impact that has had on the availability of certain replacement parts. One part in particular, a sensor that monitors the quality of diesel emissions fluid (DEF), has been of concern because the failure of the part can lead to the vehicle being unable to operate. The Engine Manufacturers Association (EMA) on behalf of its member companies has proposed an industry wide approach that would provide a software solution for vehicles with failed parts to enable them to operate temporarily while the industry works to produce more replacement parts and that, long term, would provide replacement parts through a recall program. EPA and CARB have reviewed the proposed approach and believe it is appropriate for the companies to implement the proposed solution going forward as quickly as possible.

“The manufacturers must still develop new software code and test it to ensure the software can be installed on vehicles in the field. The companies expect that they will be able to begin fixing some vehicles with failed sensors as soon as this week. The companies will also make available a similar software update for vehicles whose sensors have not failed but are among a group of vehicles where such a failure could be expected to occur to prevent a sensor failure from disabling the vehicle. This updated software is likewise expected to be available to service centers in the coming weeks.

“For more information, please contact your dealer or service center.”

How soon relief?

Of interest, of course, is timing. Just how soon will relief come from this quarter? “The companies expect that they will be able to begin fixing some vehicles with failed sensors as soon as this week.”

We reached out to a couple of West Coast centers about this. One, Freightliner Northwest, in Medford, Oregon, said they hadn’t heard a thing about this. The other, a Cummins dealership in Sumner, Washington, told us the same thing. They suggested we should “Call us back in a week or so.” The EPA speaks out but, sadly, the folks in the industry trenches haven’t heard the message.

Long groan

Prototype DEF sensor emulator in test.

Did we just hear a long groan? Yes, the EPA speaks out with positive words. We’re hopeful that even though service facilities haven’t heard anything about this, it will be far less than “a week or so” before they do. Meantime, you may want to pick up the phone and start dialing the shop nearest wherever your rig is located. Be sure to have the rig’s VIN code at hand. That will help the center locate anything new on the subject.

Meantime, the group working on the development of the DEF sensor emulator tells us that they’re hopeful they’ll have some useful information for you on building your own emulator.  No matter how long industry takes to get this “fix” in place, be it later this week or weeks down the road, those who can use this emulator will be literal miles ahead.



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1 year ago

Great that this is going to be improved, but I am still waiting on some statistics on actual numbers. If it has happened to you, it’s a big deal, but if it is 1 in 1000000 units – well

Kenneth Fuller
1 year ago

If the EPA and CARB folks had these problems with all of their vehicles, you can bet they would have an fix NOW!

George Sitek
1 year ago

After reading many articles on the DEF sensor problems, I have yet to read anything listing which diesel engines or RV manufacturers are experiencing these problems. Is there a list of which products owners should monitor closely, or which products are NOT affected?

1 year ago

Awe. Medford, Oregon’ Freightliner shop. They replaced our DEF head in 2019, long before supply and quality problems. Let’s hope I got one out of the good barrel of parts. Nice folks.

1 year ago

I’m from the
government, and I’m here to help.

Jesse Crouse
1 year ago
Reply to  tom

The only way govt. hacks can help is to “GET OUT OF MY WAY,I AM COMING THRU”. A phrase from WWII.

1 year ago

Diesel engines were supposed to be so simple, and were designed that they could run off off many different fuels (Rudolf Diesel’s original patent was for a vegetable-oil fueled engine).

Of course, government gets involved and screws everything up. Just look at the gas can.

We have two adult sons who LOVE their diesel engine pickup trucks, and every time they get together they compare stories of all the problems, electronics failures, breakdowns, expensive exhaust kits, engine tuners, and other workarounds to make the engines run as they should, and how much they spent to keep them going. I have a 1960’s Case tractor with a diesel engine that has zero electronics, and it still runs just fine with zero repairs outside of normal maintenance. No way I’d own a modern diesel engine.

Last edited 1 year ago by CLeeNick
Jesse James
1 year ago
Reply to  CLeeNick

Love your second sentence. So true.

The Lazy Q
1 year ago
Reply to  CLeeNick

So true.

Tommy Molnar
1 year ago
Reply to  CLeeNick

Everything the government touches seems to turn to ‘poo’.

Mark O.
1 year ago
Reply to  Tommy Molnar

I long for my old steel gas can from the 70’s every time I fill my lawn mower!

1 year ago
Reply to  Mark O.

They still have the old steel gas cans out there for sale you just have to look for them.

1 year ago
Reply to  Mark O.

Agree! Sometimes simple IS good! I have a couple 2-2 1/2 gallon steel gas cans that I’ve found at yard sales/thrift stores and I treasure them!
One place I have seen steel gas cans for sale is at local military surplus stores, though they seem to usually be in the 5 gallon, or roughly equivalent metric, size.

Last edited 1 year ago by CLeeNick
Stephen Malochleb
1 year ago
Reply to  CLeeNick

And sadly overpriced.

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