SEL light discussion (what's causing it?)

usmcav8or · September 28, 2021

On 8/25/2021 at 9:20 PM, Mitchy21 said:

I feel like I'm going crazy when I drive mine. 2021 5.3 Trail Boss, build date 7/21, 1,700 miles, bought just over a month ago. I swear I feel constant misfires when holding speed on the highway or going up a long slight grade. It's not pronounced at all, I don't think a passenger would even notice, almost just feels like tiny constant bumps in the road. Maybe all in my head from reading this forum too much? RPMs between 1100 and 1400. I drive the same roads every day, and I swear I didn't feel this for the first 1,500 miles. Not sure if it's misfires, or if the truck is going into 10th gear when it really shouldn't be and bogging down?

I completely understand what you are describing, ditto here as well, it's just that I have no experience with any other GM product, so I don't know if it's the tranny hunting, or if the motor is just a little loaded down at low rpm so the manner which it lumbers along is kind of normal? I also suspect I'm "feeling" the DFM system doing it's thing, which in my opinion would make the engine run a smidge rough as the cylinders are cycled off, so perhaps that's just "normal" DFM operation as opposed to misfires. It seems to run a little smoother in L9 (which purportedly shuts off DFM, but it's subtle, so hard to say for sure). It further proves what a dumb decision GM made in going down the AFM/DFM road, I would rather they have gone the Ford road (forced induction), you get way more efficiency and power out of it, and modern turbos are pretty darn reliable (especially relative to this stupid DFM system).

What really should be happening is that GM engineering should be seeing these forums and respond!

Edited September 28, 2021 by usmcav8or
typo

tootall4289 · September 28, 2021

45 minutes ago, usmcav8or said:

I took mine to dealer this a.m., mechanic pulled code P0300 (again), couldn't find anything else wrong, he asked me to drive and monitor for a couple weeks and he'll keep the service ticket open. I'm willing to let the dealer give this an honest try, but bottom line is they don't know what's wrong with it, let alone how to fix it, and really it's a design flaw from the factory. It's very concerning how many 5.3's have had this problem, I found a similar thread on another site, seems there are a slew of Trail Boss owners reporting same situation. Lemon Law's vary by state, I've already looked at how it works in mine (MD), I would like to believe that this issue can be resolved because I really do love the truck otherwise, it rides great, quiet cabin, nice radio, the 5.3 is actually a really nice motor, the 10 speed tranny does a great job, literally have nothing but praise for the truck, but obviously this situation with the SEL is absolutely 100% unacceptable. It totally baffles me what thought process led GM to conclude that the AFM/DFM was worth the hit to reliability and their brand reputation, the customer aggravation, etc. All that to get a fleet increase of 1 mpg?! Tundra's get 14-15 mpg and people love them because they are a bulletproof rock-solid reliable powerplant. What customer would chose 1 mpg if it meant introducing the complexity of DFM, nobody would be dumb enough to do that (except a GM engineer).

I will certainly report back with updates, hope others will post their experiences as well.

It would be interesting to know manufacturing dates of the troublesome trucks?

My build date is May 15, 2021

usmcav8or · September 28, 2021

mine was made in Silao plant, Guanajuato, MX, 06/2021

Mitchy21 · October 6, 2021

On 9/28/2021 at 4:17 PM, usmcav8or said:

I completely understand what you are describing, ditto here as well, it's just that I have no experience with any other GM product, so I don't know if it's the tranny hunting, or if the motor is just a little loaded down at low rpm so the manner which it lumbers along is kind of normal? I also suspect I'm "feeling" the DFM system doing it's thing, which in my opinion would make the engine run a smidge rough as the cylinders are cycled off, so perhaps that's just "normal" DFM operation as opposed to misfires. It seems to run a little smoother in L9 (which purportedly shuts off DFM, but it's subtle, so hard to say for sure). It further proves what a dumb decision GM made in going down the AFM/DFM road, I would rather they have gone the Ford road (forced induction), you get way more efficiency and power out of it, and modern turbos are pretty darn reliable (especially relative to this stupid DFM system).

What really should be happening is that GM engineering should be seeing these forums and respond!

So after I wrote this, I went on a 600 mile road trip. Filled it with premium just to see what would happen and didn't feel a thing. Haven't ran premium since and still don't feel anything. Doesn't really make sense that premium would help the situation, but I have about 1200 miles on it since getting back from that trip and I haven't noticed that it does it at all anymore.

usmcav8or · October 6, 2021

It's been a little over a week since I got mine back from the dealer and still no SEL light, but I haven't driven it very much. I'm hoping what may have happened is that when the tech updated the ecu software and did the crank relearn procedure on the first visit, that perhaps the relearn procedure was not done correctly or didn't take, I know those kinds of procedures can be glitchy and the instructions for doing them are often confusing. When I took the truck back the second time he kept it in the bay for about 45 minutes, my guess is he did the crank relearn again, (at least that's what I'm hoping), time will tell. I'll give premium a shot and see if I notice any difference, but I have to say that may be just you getting used to the truck. Speaking for myself, (now that I have 2500+ miles) mine seems to be running smoother overall as well, I don't know if that's the tranny smoothing out as it breaks-in and learns driver behavior, or if it's just me getting accustomed to the feel of the vehicle, I also noticed that after the software update it seemed to run smoother overall. I'm skeptical that premium would make a big difference in a NA V-8 motor, by design they just shouldn't be very sensitive to that kind of thing (as opposed to forced induction engines), not to mention the fact that where I live premium is about $1 more per gallon, and that's totally not acceptable to me to pay that as a huge fuel surcharge over the lifetime of the truck, it needs to be able to run on regular grade fuel.

kmeleon · October 24, 2021

So it looks like my saga with the truck will come to an end. And yesterday I took the truck to the local Toyota dealer for an appraisal and they're going to give me 50K for it. So I put $500 down on a new 22 Toyota Tundra! The best thing is since the Tundras aren't out yet I get to keep driving my truck and that number is good until my new one gets ordered and delivered.

It really is a shame, I've been a GM guy pretty much all my life but I refuse to keep this ticking time bomb any longer. Knowing that my truck falls into the lifter failure time frame, the valve spring failure time frame, the flashing Cel light that they can't fix, the shuttering on low speed slow down that's occurring,etc... I just decided enough was enough. And I'm sure they'll be people who'll say V6 twin-turbo haha, good luck. But I'll put my money that it's much more reliable then this new DFM V8 crap GM is building. I really did love my truck but all these issues have just ruined the fun that is having a new vehicle.

Yotaman · October 24, 2021

Don't think the new Toyota cannot have problems but I agree that your chances are much greater to not have issues with the Toyota. I do think Toyota is making a mistake not offering the current V-8 as a option in the 22 model but not because I think the V6 TT is not enough, Just cause in America almost everyone seems to think that bigger is always better. Best of luck with the new Toyota.

usmcav8or · October 24, 2021

Update on mine: Put about 3,000 miles on it since the second dealer visit, I called them to let them know they can close the ticket and service advisor said "I guess the second re-learn procedure did the trick", so my only advice if you have the nuisance CEL light is to make sure the mechanic does the crankshaft re-learn procedure correctly (and don't be surprised if they have to do it twice), in any case mine is now fixed. I actually really, really like the 5.3 motor, I'm getting 20 mpg in mixed driving and it has plenty of grunt when I need it, I think it's the right balance of power and mpg in a 1/2 ton for most people. The 10 speed tranny is great, trucks rides great, comfortable cabin, so I'm happy with it (for now LoL).

tootall4289 · October 29, 2021

On 10/24/2021 at 7:26 AM, kmeleon said:

So it looks like my saga with the truck will come to an end. And yesterday I took the truck to the local Toyota dealer for an appraisal and they're going to give me 50K for it. So I put $500 down on a new 22 Toyota Tundra! The best thing is since the Tundras aren't out yet I get to keep driving my truck and that number is good until my new one gets ordered and delivered.

It really is a shame, I've been a GM guy pretty much all my life but I refuse to keep this ticking time bomb any longer. Knowing that my truck falls into the lifter failure time frame, the valve spring failure time frame, the flashing Cel light that they can't fix, the shuttering on low speed slow down that's occurring,etc... I just decided enough was enough. And I'm sure they'll be people who'll say V6 twin-turbo haha, good luck. But I'll put my money that it's much more reliable then this new DFM V8 crap GM is building. I really did love my truck but all these issues have just ruined the fun that is having a new vehicle.

Best of luck Kmeleon

kmeleon · October 29, 2021

15 hours ago, tootall4289 said:

Best of luck Kmeleon

I appreciate it. I'll be around for awhile, it's going to be the end of the year at best before the Tundra shows up.

kmeleon · November 3, 2021

Update: GMC dealer did another update to the PCM today. This update they tell me should fix the remaining 10% of the CEL issue (after the last update its been significantly better) as well as the shudder issue around 13mph upon decel. This included the crankshaft sensor relearn. I'm going to pick it up tomorrow, we shall see.

Edited November 3, 2021 by kmeleon

Skeeterhawk01 · November 4, 2021

Dude, your truck is in the buyback window. Demand a buyback and be done with GM. They are building junk right now and they know it.

I'm currently dealing with a problem on my 2017 and waiting to get the truck back soon from the stealership.

Truck has just over 30K miles and this crap started 5 months ago at 28K miles. They replaced all the injectors, in which it didn't fix the problem. Then they said they found a bad lifter on ##3. Don't ask me why they didn't find this in the first place.So they replaced all the lifters on that side. Problem went away. Until this last Sunday. Threw code P0303. They say bad injector on #3 and replaced it. Suppose to get the truck back tomorrow. I will not be buying another GM product.

kmeleon · November 6, 2021

Update: I'm thinking they fixed the truck. The latest program and crankshaft sensor relearn has definitely fixed the shudder problem when slowing down. I haven't seen a Cel light yet but it's only been 2 days.

As far as a buy back goes, it actually makes more sense to trade it in as I'm getting what I paid for it and I get the tax credit for the trade in. The only question now is whether or not I can order the exact Tundra I want because I guess Toyota is being funny about these allocations to the dealers. It also seems like the third gen Tundras are a bit more expensive than I thought. We shall see in the coming days

Edited November 6, 2021 by kmeleon

usmcav8or · November 6, 2021

I would give the GM truck a little while, see how it goes, mine hasn't given me a lick of trouble ever since they re-did the crankshaft re-learn procedure, maybe that will be the case with yours as well? I think Toyotas are great, but I also really don't like buying the first year (or two) of any new model vehicle, seems like they always have some issues that require design modifications. I'm hoping to own this truck for 4-5 years, put 100k on it, by that time the Tundras will be a known quantity and there will be other new stuff on the market to choose from. I personally love turbos, you get a huge increase in power for a small risk of having to eventually replace the turbo, which isn't even a big deal nowadays as the turbos are becoming super reliable, so although I really like the power delivery of this 5.3L, my guess is my next truck will be forced induction, I really don't see NA engines hanging around that much longer anyway, seems like every manufacturer will soon be forced induction as the mainstay offering. I really love this AT4, as long as I don't have any more issues, I'll enjoy it for a few years.

kmeleon · November 6, 2021

56 minutes ago, usmcav8or said:

I would give the GM truck a little while, see how it goes, mine hasn't given me a lick of trouble ever since they re-did the crankshaft re-learn procedure, maybe that will be the case with yours as well? I think Toyotas are great, but I also really don't like buying the first year (or two) of any new model vehicle, seems like they always have some issues that require design modifications. I'm hoping to own this truck for 4-5 years, put 100k on it, by that time the Tundras will be a known quantity and there will be other new stuff on the market to choose from. I personally love turbos, you get a huge increase in power for a small risk of having to eventually replace the turbo, which isn't even a big deal nowadays as the turbos are becoming super reliable, so although I really like the power delivery of this 5.3L, my guess is my next truck will be forced induction, I really don't see NA engines hanging around that much longer anyway, seems like every manufacturer will soon be forced induction as the mainstay offering. I really love this AT4, as long as I don't have any more issues, I'll enjoy it for a few years.

It really will depend on a couple things. Did the shop really fix it? Will the Toyota dealer order me exactly what I want?

I'm not set in trading it, but these issues (along with the valve spring and lifter batch issues that my truck does fall in the window of) really have turned me off...its ruined my first year with the truck and left a bad taste in my mouth. But the stars will have to align with Toyota for me to trade it in. They're more expensive than I thought they would be but when you look at the tech I'd be getting vs my 21 gmc you can understand paying a bit more. The camera package is amazing on the new tundra which would be great for pulling my new car trailer next year.

We shall see.