!#@%* Emissions System

[426ted]

Hey everyone, back in May the check engine light came on and I got the warning in the DIC (pictures attached are from today but it read the same). Took it to the dealer. Tech could not find anything wrong though he did pull 2 codes. All summer it was fine until last week. The check engine light and notice came on for a bit but went out before I could get to the dealer. I have a big road trip planned tomorrow and guess what, it's back. I have noted that this truck pushes blue smoke occasionally when accelerating. Dealer was told last year and they indicated no oil loss between changes. Anyways, I am curious if other members have experienced this. Truck is a 2024 3500 Duramax. Cheers.

[Dunn]

did you miss a cpl of regens?

do you have a guage to tell you when?

 

mine had this first week I had it, since then I bought an I dash and have completed regens when they came up and no issues since......

[EXSlider400]

4 hours ago, Dunn said:

did you miss a cpl of regens?

do you have a guage to tell you when?

 

mine had this first week I had it, since then I bought an I dash and have completed regens when they came up and no issues since......

This would also be my suggestion. I had the previous generation L5P and if I was making a lot of short trips, taking a good long road trip always seemed to help the regen do its thing. Also make sure you’re using good DEF….(not old stock as it degrades quickly) If you’re getting it out of a box/container, check the date (there’s a way to decipher the printed code on the box …just google it.). If you’re just pumping it in, make sure it’s a good high-use busy station.

Edited October 3, 2025 by EXSlider400

[426ted]

I take it on quite a few long trips, plus highway speeds in the lower mainland, so I didn't think it was a regen problem. I got it back today. Error code P122D. They replaced the throttle plate as there were numerous chips on the backside along the sealing edge. Like, WTF, chipped throttle blade? Anyways, glad to have the truck back, but I don't trust it yet.

[PBNB]

It might be a good time to grab a Banks monitor. I saw them on sale recently.

 

I have one and it tells me what is going on with regens and other info. I have it set to track trans and oil temps mostly and regens. Could the message on your dash just be telling you that the DEF is low? 

[426ted]

I think I should update this thread. Got it back from the dealer a few weeks ago. Here is the breakdown from the worksheet I got from the dealership:

 

P122D Current code. Followed P122D-00 diagnostic steps, clear code, repeat.

Inspect throttle plate assembly for damage/obstruction/coking. Found carbon build-up by nothing restricting the throttle plate.

Remove for more thorough inspection. Backside of throttle plate is chipped in multiple spots along the sealing edge.

Clean area and install replacement throttle plate.

 

WTF is carbon building up on the throttle plate? Do these trucks need a catch can? Mileage is 53000km.

 

 

 

[customboss]

6 minutes ago, 426ted said:

I think I should update this thread. Got it back from the dealer a few weeks ago. Here is the breakdown from the worksheet I got from the dealership:

 

P122D Current code. Followed P122D-00 diagnostic steps, clear code, repeat.

Inspect throttle plate assembly for damage/obstruction/coking. Found carbon build-up by nothing restricting the throttle plate.

Remove for more thorough inspection. Backside of throttle plate is chipped in multiple spots along the sealing edge.

Clean area and install replacement throttle plate.

 

WTF is carbon building up on the throttle plate? Do these trucks need a catch can? Mileage is 53000km.

 

 

 

Use better fuel. Can you access Canadian CO-OP diesel? 

[426ted]

I'd say I fill up at Chevron 95% of the time. We do have a Co-op locally. Better Diesel you think? I've started adding Hot Shot diesel treatment since I got the truck back.

[customboss]

11 hours ago, 426ted said:

I'd say I fill up at Chevron 95% of the time. We do have a Co-op locally. Better Diesel you think? I've started adding Hot Shot diesel treatment since I got the truck back.

The CO-OP fuel is better in refining and additives that are hot blended. Use it. Change fuel filters more often if needed. 
What region of Canuck land are you located? 

[426ted]

Located in Ladner. Paying $1.74/liter last fill. Bloody crooks. Where abouts are you?

[customboss]

On 10/22/2025 at 8:09 AM, 426ted said:

Located in Ladner. Paying $1.74/liter last fill. Bloody crooks. Where abouts are you?

Southern Colorado USA, 40 miles east of Alamosa up mountain. 

[customboss]

On 10/22/2025 at 8:09 AM, 426ted said:

Located in Ladner. Paying $1.74/liter last fill. Bloody crooks. Where abouts are you?

Vancouver BC. 

[customboss]

On 10/22/2025 at 8:09 AM, 426ted said:

Located in Ladner. Paying $1.74/liter last fill. Bloody crooks. Where abouts are you?

Each Province in canuckland is different on accessibility of high quality locally refined fuels so do some footwork.