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Take it to the dealer if it's under warranty. There is freeze frame data the dealer can access and use to aid diagnosis. Also, a flashing check engine light means that the PCM has detected a misfire severe enough to potentially damage the catalysts. If the misfire continues, it could lead to an expensive catalyst repair down the road. The more documentation you have that the root cause began under warranty, the better off you will be.

Nice build! Following for additional updates.

Subscribed. Sounds like a badass swap.

If the system is vacuum actuated, check all the lines for cracks or other abnormalities. A leak can prevent 4x4 engagement.

I'm betting it has to do with the pickup's spring package and/or payload rating. Wouldn't surprise me if all half tons came with that disclaimer. A 3/4 ton is much better suited for having 2,000+ pounds in the bed.

Nice work! Coming together quickly.

There ya go! Glad to hear you got the problem at least diagnosed. May not be fun work, but it will be rewarding once its back together and running well. Keep up the good work.

The AFM lifters are controlled by oil pressure I believe, but I'm no expert. I don't want to guide you down the wrong path. I'm happy to give you my opinion, but don't want my opinion to cost you a bunch of money. I'm just throwing the AFM lifter out as a possibility. Without tearing it down again and inspecting the valvetrain and valvetrain control circuits (AFM lifter namely), I'm out of ideas.

Quick engine stats: VORTEC 6.0L Gen IV V-8 (LFA) HYBRID TRUCK ENGINE 2009 Model Year Summary · New Engine for 2009 Chevrolet Silverado Hybrid and GMC Sierra Hybrid. Continues from 2008 model year as carryover model for Chevrolet Tahoe Hybrid, GMC Yukon Hybrid, Cadillac Escalade. Hybrid. · Variable Valve Timing · Active Fuel Management · Variable Displacement Oil Pump · Returnless Fuel Injection with Stainless Steel Fuel Rail · Advanced Electronic Throttle Control · E67A Engine Control Module · 58X Ignition System · Enhanced Noise, Vibration and Harshness Control · Late Intake Valve Closing

Thanks for the video. That is a dead miss...absolutely no contribution from that cylinder. Did some research and confirmed that the hybrid rigs did indeed get Atkinson cycle engines. They also have AFM. If that cylinder is one that the AFM deactivates, I'd inspect #4's lifters to ensure they aren't permanently collapsed. The AFM lifters are designed to collapse under normal operation, but they may fail to where that cylinder is essentially permanently deactivated.

After this work, you have: -Eliminated spark concerns (spark plug testing good = plug, wire, and coil are ok. -Eliminated fueling concerns (confirmed injector pulse signal = PCM knows when to fire cylinder #4, replaced #4 injector) The fact that the misfire is concentrated on a single cylinder means timing isn't the issue, so we can rule that out. Short of some freak electrical problem, this diagnostic path seems to be leading us down the mechanical path. What is the compression like on #4 compared to the other cylinders? A flat cam lobe can prevent the valves from opening or sealing properly. Did you inspect the cam lobes when you had everything apart? A cracked valve spring may not have the amount of spring pressure required to properly shut the valves and seal the cylinder. Did you inspect the valve springs on #4 when you had the head off? Also, just out of curiosity, is this engine a fixed Atkinson cycle design or variable? (can switch between Otto and Atkinson)

FM radio won't be affected, but I'm willing to bet AM reception will be effectively useless after the antenna modification. AM requires the antenna to be a certain length and height in the air. 32" is ringing a bell, but don't quote me on that. I relocated my antenna under my hood and lost 100% of my AM radio reception FWIW.

+1 on the Corvette servo's effectiveness. However, to be fair, 170k is a decently long life for the 4L60E trans. As mentioned, its a solid upgrade for the price and may prolong the inevitable. But don't expect it to cure your problems permanently.

You can't simply say the compressor is/isn't bad or the system is/isn't empty with the amount of information contained in the original post. OP, is the clutch actually kicking on? A clutch that doesn't engage could be a system low charge or any number of failed sensors. If the compressor isn't running, your high and low side pressures would be equal. If you have access to an A/C machine, pull all the refrigerant out of the system and compare the charge removed to the charge specification. If the charge is low enough, the pressures won't be high enough for the PCM to decide to operate the compressor relay. The Duramax should run a fixed displacement, cycling compressor. Forgive me if that statement is erroneous as I haven't done GM A/C work in a while. Luckily, the compressor on a Duramax is in an extremely accessible spot...

Interested to hear the verdict. My parents had a Suburban with the 4L60E that had identical symptoms to the ones you're experiencing. It ended up being traded in before it was diagnosed.

Still hanging out with 325k here. Original 4.8, rebuilt 4L60E, original rear end. Interior looks awesome after the swap, A/C blows in the high 30's / low 40's on a 100℉ day. The truck still runs and drives awesome, and looks decent for what it is, too. Sadly, it doesn't get driven but once or twice a month now. The fuel mileage didn't cut it when my commute went from 12 miles round trip to 36. I bought a little beater so the truck sits now.

Check the pressure in the spare tire. It could have gotten low enough to trip the light and the timing was just a coincidence.

Good to hear you got it figured out!

A bad socket can cause a bad ground (poor connection). Or your ground could still be loose and / or dirty. Try putting the fuse back in and pull each bulb that is powered by that fuse. Start with the dual filament bulbs (as said above, they are generally the problem). After pulling each one, check to see if the lights function properly and get back to us.

I agree with the loose / dirty ground. My computer isn't loading the diagram (or anything else for that matter...) so I can't tell you where it's grounded at.

Yeah, as long as you remove the headlights from the circuit. Unplug them, remove the bulb, whatever works.

See if you can get a helper to keep a foot on the brake (or rig up a broomstick or something similar). Turn the headlights on. Then remove one headlight bulb and see if the brake lights act normally. If there're still acting up, try the other bulb. That's all assuming you didn't put new headlights in it. Let me know if that doesn't fix it and I'll look at the diagram when I can and see what else could be going on.

A bad bulb can actually cause problems like this. The third brake light has it's own circuit, which explains why it still functions. And since the third brake light works, that eliminates the fuse and brake switch as the trouble maker. That means your problem is occurring from the brake light switch to the bulb. You could try swapping out each brake light / tail light bulb with a new one and see if the problem persists. For the price, ya can't compain.