Brand new Sierra 5.3 CEL flashing

kmeleon · February 27, 2021

10 hours ago, Z71TrailBoss said:

My 2021 Trail Boss with a 5.3L 10 speed auto with 3,500 miles is at the local dealer for the second time with this problem. Which code reader are you going with?

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https://www.amazon.com/dp/B005NLQAHS/ref=cm_sw_r_cp_apa_fabc_TBAKR9CP8Q5R1YB2QKFC

Please update what they find with your truck. Very interested. Good luck!

1997SierraSLT · February 27, 2021

With as many times you’re going to see that CEL flashing over the lifetime of ownership, GM should just include a scan tool with every new vehicle purchase.

redwngr · February 27, 2021

Maybe??

https://gm-techlink.com/?p=14363

Misfire Due to Collapsed Lifter

February 10, 2021

Some 2019-2021 Silverado, Sierra; 2021 Tahoe, Suburban, Yukon and Escalade models equipped with the 5.3L V8 engine (RPO L84) or 6.2L V8 engine (RPO L87) may have a misfire condition with a bent pushrod that leads to a collapsed lifter or the lifter comes apart. Misfire DTCs P0300 – P0308 may be set.

If Service Information diagnostics lead to a collapsed lifter and/or a lifter that has come apart, it is recommended to replace the valve lifter guide and the four lifters. (Fig. 23) It is not necessary to replace the oil control solenoid valve.

Fig. 23

Note the installed position of the valve lifter guide. The notched area of the lifter guide aligns with the locating tab on the engine block. (Fig. 24) Install the new valve lifter guide and the lifters as an assembly.

Fig. 24

The part will be requested back by GM engineering. Be sure to mark the guide to show the location of the cylinder for inspection. Do not cover the date code.

For more information, refer to #PIP5776.

Stephen Gaze · March 16, 2021

Just found this topic. Picked up my brand new 1500 LT Trail Boss yesterday. On way home from dealer, got an flashing CEL for ~10 to 15 secs sitting at a stop light. Did not make it to dealer today. Running errands this afternoon, got another 10-15 sec flashing CEL when accelerating moderately at ~3k rpm. Truck has a total of 96 miles on it. Swung by a local mechanic to read codes and there was nothing (had been started/stopped 3 times since CEL). Heading to dealer tomorrow to be there when they open at 7AM.

Truck was a special order (crew cab/standard bed). Hoping it is something simple or at worst coil packs. Collapsed lifter/bent push rod would not make me happy.

kmeleon · March 17, 2021

2 hours ago, Stephen Gaze said:

Just found this topic. Picked up my brand new 1500 LT Trail Boss yesterday. On way home from dealer, got an flashing CEL for ~10 to 15 secs sitting at a stop light. Did not make it to dealer today. Running errands this afternoon, got another 10-15 sec flashing CEL when accelerating moderately at ~3k rpm. Truck has a total of 96 miles on it. Swung by a local mechanic to read codes and there was nothing (had been started/stopped 3 times since CEL). Heading to dealer tomorrow to be there when they open at 7AM.

Truck was a special order (crew cab/standard bed). Hoping it is something simple or at worst coil packs. Collapsed lifter/bent push rod would not make me happy.

Please make sure you post here once you have the truck looked at.

Stephen Gaze · March 17, 2021

13 hours ago, kmeleon said:

Please make sure you post here once you have the truck looked at.

Well, here is the update.

Like we used to say in Navy aircraft maintenance. A799. Could not duplicate.

No codes. They pulled the plugs and all looked good. Seemed to run a little smoother on way home so maybe just a slightly loose wire.

Anyway, issue is documented. Did have an interesting conversation with my sales person and the manager afterwards. Service rep comes out and tells me I have an aftermarket CAI installed and that can cause codes. I correct him and tell him that, "No. that is the factory performance package that was installed by GM." He keeps babbling about aftermarket CAI. How can you be called a service advisor if you don't know what is stock and what isn't?

Stephen Gaze · April 10, 2021

And an update. Driving today with 305 miles on truck. Flashing CEL for about 15 sec. Went away. Drove another 60+ miles with no issues (and best gas mileage I have recorded so far).

Swung by O’Reilly and they didn’t see any codes. Have a dealer appointment for 4/19 since truck was scheduled to get ceramic coated next week.

May try to swing by dealer service tomorrow. Not sure how they would diagnose a pushrod or lifter issue without pulling the valve covers. No apparent lifter noise that I can hear.

I also read something about oil level. As in too much oil. Any info on that? I checked my oil and it is above the cross hatch on the dipstick. Basically filling the notch above the hatched area but not onto the solid upper part of the dipstick.

Edited April 10, 2021 by Stephen Gaze

Stephen Gaze · April 10, 2021

Update. Decided to swing by service department today. They found codes for intermittent misfire on cylinder #1. No appointments available till Tuesday but the service advisor said bring it in Monday AM. Less than 400 miles on truck so this is going to take priority over the ceramic coating.

SteveG · April 15, 2021

On 4/10/2021 at 4:15 PM, Stephen Gaze said:

Update. Decided to swing by service department today. They found codes for intermittent misfire on cylinder #1. No appointments available till Tuesday but the service advisor said bring it in Monday AM. Less than 400 miles on truck so this is going to take priority over the ceramic coating.

So, they could not duplicate. Had generic P0300 codes. Cleared now. Done 200 miles since with no issues. Fingers crossed.

Stephen Gaze · April 18, 2021

And at 666 miles, flashing CEL is back. This is getting ridiculous. Back to dealership tomorrow.

SteveG · April 19, 2021

Well, this time, the tech found three loose manifold bolts. Vacuum leak could have been the issue causing a screwed up air/fuel ratio. Tended to happen when engine was in a high vacuum condition. Fingers crossed.

lebag335 · April 19, 2021

2 hours ago, SteveG said:

Well, this time, the tech found three loose manifold bolts. Vacuum leak could have been the issue causing a screwed up air/fuel ratio. Tended to happen when engine was in a high vacuum condition. Fingers crossed.

Tech have any idea as to why they became lose?

Stephen Gaze · April 19, 2021

3 minutes ago, lebag335 said:

Tech have any idea as to why they became lose?

Not that they told me. I now have three documented visits for the same issue. Looking closely at FL Lemon Law.

kmeleon · April 19, 2021

When would a high vacuum condition occur? First few minutes after sitting? Because both times mine has done it, it was within a 1/2 mile of leaving my house after sitting for an hour.

Edited April 19, 2021 by kmeleon

SteveG · April 20, 2021

7 hours ago, kmeleon said:

When would a high vacuum condition occur? First few minutes after sitting? Because both times mine has done it, it was within a 1/2 mile of leaving my house after sitting for an hour.

High vacuum can occur when you are at light throttle or when throttle closes after accelerating.