New bulletin/Campaign 6.2 L87

eppieguy · September 2, 2025

Had mine inspected and passed, they change the oil to 0W-40, changed the cap and sent me on my way. I really wonder if anyone fails this test that they've come up with?

2023 Sierra Denali Ultimate, 24k

newdude · September 2, 2025

49 minutes ago, eppieguy said:

Had mine inspected and passed, they change the oil to 0W-40, changed the cap and sent me on my way. I really wonder if anyone fails this test that they've come up with?

2023 Sierra Denali Ultimate, 24k

Yes. Our sister store got its first test fail.

MrLeadFoot · September 2, 2025

1 hour ago, newdude said:

Yes. Our sister store got its first test fail.

Do you happen to know if the failure was based purely on the pico test only, or if it had already shown symptoms and/or thrown a code?

newdude · September 2, 2025

3 hours ago, MrLeadFoot said:

Do you happen to know if the failure was based purely on the pico test only, or if it had already shown symptoms and/or thrown a code?

I gotta find out for sure but from what I heard so far, no codes when it came in. Was in for an oil change, this recall and the reprogram recall to add more software for detecting P0016 "sooner". During the recall test, the Pico data was analyzed by the software and it came back as "FAIL".

GETGONE · September 2, 2025

I guess that's hopeful news that it did detect something before failure since I haven't heard that anywhere else yet.

SierraStorm21 · September 2, 2025

Yeah after hearing the email story that DonsLife read on his channel last week where the owner was having performance issues and no one could track it down, then coming in for the test, it passes, but then the tech heard something that didn't sound right. Dug a little further and found it was on the verge of imploding, and is getting a new engine, didn't inspire any confidence about the test and it's validity

carkhz316 · September 2, 2025

2 hours ago, newdude said:

I gotta find out for sure but from what I heard so far, no codes when it came in. Was in for an oil change, this recall and the reprogram recall to add more software for detecting P0016 "sooner". During the recall test, the Pico data was analyzed by the software and it came back as "FAIL".

Sorry, I gotta chuckle a little bit if they're using software to 'analyze' a scope waveform; especially for a simple cam/ crank correlation. I use a 4425a almost daily (Indy shop) and you can see chain elongation ("stretch") down to the degree if you have a known good to compare to, or just know the pattern for the reluctor(s). The image below is from one I diagnosed earlier this year that WAS setting a P0016 but without any other symptoms (starts and runs fine). This one had actually jumped time (was off by a tooth) and measured in at about 11 degrees retarded; which is the minimum of the code-set criteria. The measured waveform is actually post-repair, but the red and green highlights point to where the blue trace rising edge (cam tooth) was on the truck before the repair. This is a quick and easy test to perform in a shop with even a basic 2-channel scope. I do wonder how they're using this information to determine engine integrity since I thought the result was spinning bearings and ejecting connecting rods.

Edited September 2, 2025 by carkhz316

MrLeadFoot · September 2, 2025

1 hour ago, GETGONE said:

I guess that's hopeful news that it did detect something before failure since I haven't heard that anywhere else yet.

Yes, that would be good news, but @newdude doesn't know for sure, yet. Let's hope he finds out for sure that it went down like he suspects it did.

Edited September 2, 2025 by MrLeadFoot

MrLeadFoot · September 2, 2025

17 minutes ago, carkhz316 said:

Sorry, I gotta chuckle a little bit if they're using software to 'analyze' a scope waveform; especially for a simple cam/ crank correlation. I use a 4425a almost daily (Indy shop) and you can see chain elongation ("stretch") down to the degree if you have a known good to compare to, or just know the pattern for the reluctor(s). The image below is from one I diagnosed earlier this year that WAS setting a P0016 but without any other symptoms (starts and runs fine). This one had actually jumped time (was off by a tooth) and measured in at about 11 degrees retarded; which is the minimum of the code-set criteria. The measured waveform is actually post-repair, but the red and green highlights point to where the blue trace rising edge (cam tooth) was on the truck before the repair. This is a quick and easy test to perform in a shop with even a basic 2-channel scope. I do wonder how they're using this information to determine engine integrity since I thought the result was spinning bearings and ejecting connecting rods.

You are bringing up something I've been wondering about ever since this "test" came out. I can't help but wonder if this recall "resolution" is smoke and mirrors to placate the NHTSA, and that the picoscope really can't tell them anything until something has already gone wrong. I would think that there are variations in every motor, which would create quite a wide range from which to try and detect something "abnormal", and by the time something abnormal was detected, it would already have developed other symptoms, or soon would, anyway. But, this way, GM can at least they can show they made an "honest" attempt to help detect and pre-empt failures.

Edited September 2, 2025 by MrLeadFoot

newdude · September 3, 2025

15 hours ago, carkhz316 said:

Sorry, I gotta chuckle a little bit if they're using software to 'analyze' a scope waveform; especially for a simple cam/ crank correlation. I use a 4425a almost daily (Indy shop) and you can see chain elongation ("stretch") down to the degree if you have a known good to compare to, or just know the pattern for the reluctor(s). The image below is from one I diagnosed earlier this year that WAS setting a P0016 but without any other symptoms (starts and runs fine). This one had actually jumped time (was off by a tooth) and measured in at about 11 degrees retarded; which is the minimum of the code-set criteria. The measured waveform is actually post-repair, but the red and green highlights point to where the blue trace rising edge (cam tooth) was on the truck before the repair. This is a quick and easy test to perform in a shop with even a basic 2-channel scope. I do wonder how they're using this information to determine engine integrity since I thought the result was spinning bearings and ejecting connecting rods.

EDIT: Linking an earlier version of the recall here that's from this very thread: https://www.gm-trucks.com/forums/applications/core/interface/file/attachment.php?id=182274&key=25bd8ff5fd2a227a83b28b5554b53c6d

They aren't using the Picoscope test to analyze for P0016 nor is it to analyze cam/crank correlation. If one of these recalled 6.2s comes in with P0016 set, it gets an engine, full stop.

This test is done with a special tool they sent to dealers. The tool is a harness with a knock sensor on it. The knock sensor gets installed to an open M8 threaded boss on the left side of the block, and the Pico side of the harness gets attached to Channel B on the Pico.

Dealers do NOT use the Pico branded software for this test; they use the GM NVH software for this (both software are installed on shop computers, the GM NVH and the Pico one). The GM NVH software then gets set up to use the supplied sensor/harness as a microphone and then a 30 second or more clip gets recorded. That clip then gets analyzed by a special test that is in GM SPS2 (service programming) and will pass or fail the data.

So far engines that I've seen pass pull in the realm of 50-65dB sound range at the 2000rpm the data is recorded at.

Edited September 3, 2025 by newdude

MrLeadFoot · September 4, 2025

On 9/3/2025 at 6:52 AM, newdude said:

So far engines that I've seen pass pull in the realm of 50-65dB sound range at the 2000rpm the data is recorded at.

Nice to hear this tidbit of info. Thanks, newdude, for also keeping us updated on your findings.

carkhz316 · September 5, 2025

On 9/3/2025 at 8:52 AM, newdude said:

EDIT: Linking an earlier version of the recall here that's from this very thread: https://www.gm-trucks.com/forums/applications/core/interface/file/attachment.php?id=182274&key=25bd8ff5fd2a227a83b28b5554b53c6d

They aren't using the Picoscope test to analyze for P0016 nor is it to analyze cam/crank correlation. If one of these recalled 6.2s comes in with P0016 set, it gets an engine, full stop.

This test is done with a special tool they sent to dealers. The tool is a harness with a knock sensor on it. The knock sensor gets installed to an open M8 threaded boss on the left side of the block, and the Pico side of the harness gets attached to Channel B on the Pico.

Dealers do NOT use the Pico branded software for this test; they use the GM NVH software for this (both software are installed on shop computers, the GM NVH and the Pico one). The GM NVH software then gets set up to use the supplied sensor/harness as a microphone and then a 30 second or more clip gets recorded. That clip then gets analyzed by a special test that is in GM SPS2 (service programming) and will pass or fail the data.

So far engines that I've seen pass pull in the realm of 50-65dB sound range at the 2000rpm the data is recorded at.

I hadn't seen your linked file yet, so I wasn't aware of the scope of their testing parameters. Like I mentioned, I just work in an independent repair facility, so the majority of items I'm working on aren't typically warranty or recall items. Anyway, the P0016 is literally 'cam/ crank correlation fault', so you could understand how it could be interpreted in certain instances.

But I see what you're getting at. They're just using the Pico NVH interface to perform an isolated vibration/ knock test basically, and if it falls outside of the passing criteria, then the engine is about to let loose, and P0016 just means its way past well done in this context. I'll have to try it out and measure my brothers rig ('23 Suburban HC) to see if his is about to grenade.

WeGone · September 9, 2025

So went to my GM dealer today to sell my 6.2 and buy a 2500, This was the response I got!!

Dealer: So the VIN# tells alot...I can't buy your truck anyway. There is an open recall with no remedy and has been put on the stop sale list...Manufacturer dealers cannot sell them. It would sit on the lot until there is a remedy and there is no expected date of remedy.

Me: So all it needs to to have the test done and it gets a 10year 150k warranty. You as a dealer should know this and can have it done. I as a GM customer have to wait in line. I have addressed this with GM many times.

Dealer: I understand what you are saying. I am simply passing on what my GM is saying...we have several already parked on the back line with this issue waiting for the remedy on the stop sale. He informed me that until it is lifted or corrected we cannot purchase it.

MrLeadFoot · September 9, 2025

7 minutes ago, WeGone said:

So went to my GM dealer today to sell my 6.2 and buy a 2500, This was the response I got!!

Dealer: So the VIN# tells alot...I can't buy your truck anyway. There is an open recall with no remedy and has been put on the stop sale list...Manufacturer dealers cannot sell them. It would sit on the lot until there is a remedy and there is no expected date of remedy.

Me: So all it needs to to have the test done and it gets a 10year 150k warranty. You as a dealer should know this and can have it done. I as a GM customer have to wait in line. I have addressed this with GM many times.

Dealer: I understand what you are saying. I am simply passing on what my GM is saying...we have several already parked on the back line with this issue waiting for the remedy on the stop sale. He informed me that until it is lifted or corrected we cannot purchase it.

Are you serious?! So, we have loss of value due to the recall. Lawsuits should be coming out the ying-yang right now. How do we sign up? No wonder Mary Barra just sold 40% of her stock holdings in her own company!

Edited September 9, 2025 by MrLeadFoot