6.2 intake and TB on 2020 silverado 5.3. P0171 and P0174

Firehawk99 · October 18, 2020

So I installed a 6.2 intake and TB on my 2020 silverado trail boss 5.3. I took it for a ride and the transmission was shifting wonky so I shut it off for a few minutes and then restarted it. It shifted much better and noticed a big seat of the pants difference in power, especially off the line. Thought all was well. So I took it on a long ride on the interstate and she ran great. When I got off and was back to some stop and go the CEL came on and threw 2 codes. P0171 and P0174. Looks like the engine is running lean. I have a corsa cold air intake and an AFE muffler. I put the old 5.3 intake back and cleared the codes and all well again, except for the missing power. Looks like I'll be stuck with the stock intake untill someone can come out with a reasonably priced tuner. If you guys have any other ideas on what else I could try please let me know. Thanks.

CamGTP · October 18, 2020

Without a tune you are out of luck. Doubtful anybody is going to come out with a tuner that is plug and play. The encrypted factory computers won't allow for that. That's why a whole new computer from HP Tuners is the only way.

Firehawk99 · October 18, 2020

Yeah, this really stinks. This was one mod that I could really feel an increase in power! Much better throttle response.

Gangly · October 19, 2020

If you leave it on there the S-Trims and L-Trims will eventually compensate for the lean readings. A tuned computer is great because there is no real need for adjustment, but you can still do minor bolt-ons without a tune. You just need to give the computer time to adjust, which might take several cycles, but the S-Trims will correct the L-Trims and the computer will gradually adjust the fuel ratios over time to compensate.

Firehawk99 · October 19, 2020

5 hours ago, Gangly said:

If you leave it on there the S-Trims and L-Trims will eventually compensate for the lean readings. A tuned computer is great because there is no real need for adjustment, but you can still do minor bolt-ons without a tune. You just need to give the computer time to adjust, which might take several cycles, but the S-Trims will correct the L-Trims and the computer will gradually adjust the fuel ratios over time to compensate.

Thanks. I'll give it a shot again and see if it works. I saw something about a TB relearn procedure where you start up the truck and let it idle for 3 min. shut it off and do it again. Clear any codes that show up and you should be good. I dont know if this applies to the 2019-2020's but its worth an shot.

lapoolboy · October 20, 2020

10 hours ago, Gangly said:

If you leave it on there the S-Trims and L-Trims will eventually compensate for the lean readings. A tuned computer is great because there is no real need for adjustment, but you can still do minor bolt-ons without a tune. You just need to give the computer time to adjust, which might take several cycles, but the S-Trims will correct the L-Trims and the computer will gradually adjust the fuel ratios over time to compensate.

Yep, and as it gradually adjusts the tables and adds more fuel to richen, that "seat of the pants" feel fades.

Firehawk99 · October 20, 2020

41 minutes ago, lapoolboy said:

Yep, and as it gradually adjusts the tables and adds more fuel to richen, that "seat of the pants" feel fades.

Lean is mean!

Firehawk99 · October 20, 2020

Well I figured out the problem. There was a hairline crack in the intake which caused a vacuum leak. So I ordered a new one from GM Parts Direct. $150.00 shipped. I'll keep ya updated when i install the new one.

18 hours ago, lapoolboy said:

Yep, and as it gradually adjusts the tables and adds more fuel to richen, that "seat of the pants" feel fades.

Lean is mean!

CamGTP · October 21, 2020

On 10/19/2020 at 9:14 AM, Gangly said:

If you leave it on there the S-Trims and L-Trims will eventually compensate for the lean readings. A tuned computer is great because there is no real need for adjustment, but you can still do minor bolt-ons without a tune. You just need to give the computer time to adjust, which might take several cycles, but the S-Trims will correct the L-Trims and the computer will gradually adjust the fuel ratios over time to compensate.

Not exactly. The base calibration is still the same and it will always report that it's lean no matter what. The fuel trims will compensate for the fueling error but because there is still that huge error in fueling the codes will always be tripped. It's not going to say "Hey guys, the word on the street is that the new normal is 15-20% lean all the time and we are going to work with it". It can't just modify it's own fueling tables to give itself that amount of fuel. It's going to use the trims and the trims being the ones adding in all the fuel is what trips the codes.

You are also forgetting that fuel trims do not function in open loop and that is where full throttle is. It can be lean there and the computer can do nothing to compensate for that. Even if the long term fuel trim has a carry over into power enrichment it will still be wrong.

I've dealt with far too many tunes be wrong because the airflow model was completely incorrect. The airflow model and torque model must be accurate for all things to function smoothly.

Edited October 21, 2020 by CamGTP

Gangly · October 22, 2020

Your are correct, but a cold air intake is not a 15-20 percent change in air flow and shouldn't create a situation that the computer couldn't adjust to without throwing a code. A cracked CAI, like he stated, definitely would if the crack was behind the MAF, but I bet once he gets his new intake the code disappears

Firehawk99 · October 23, 2020

4 hours ago, Gangly said:

Your are correct, but a cold air intake is not a 15-20 percent change in air flow and shouldn't create a situation that the computer couldn't adjust to without throwing a code. A cracked CAI, like he stated, definitely would if the crack was behind the MAF, but I bet once he gets his new intake the code disappears

To clarify the crack was in the 6.2 intake manifold. Which is obviously after the MAF. I agree I think the codes will go away with the new intake.

Firehawk99 · October 30, 2020

So I recieved the new 6.2 intake this morning and installed it right away. I did a manual throttle body relearn and took her for a ride. No vacuum leaks this time, and she runs awesome! The transmission shifted perfectly and the throttle response was much improved. I drove it all afternoon with mulitiple shutdowns and restarts. Zero codes were thrown and I am very pleased with the results.

Jake Hammond · November 1, 2020

I did the same thing and now have the exact same problem... I changed my 5.3 out for a ported 6.2 intake and TB. Everything was great I had the set of the pants feel too...I went on a 50 mile trip and the CEL came on with code P0171... Fuel economy is terrible now and there's some funny shifts in the trans and it's slipped a few times. I have a tune to begin with but put parts on after like a AFE CAI and Corsa CAT back... the CEL came on 60 miles after intake and TB were installed... How did you find the crack in your intake?

Firehawk99 · November 1, 2020

Come to find out I also had a vacuum leak in my cold air intake which was after the MAF. Put the truck in park and let it idle for a few minutes. If it doesn't have a steady idle you have a small leak. Buy some starting fluid and spray it on all the hoses and fittings one at a time. If you notice a change in the idle when you spray it on a particular fitting you have found your leak. If you dont notice anything move on to the intake and do the same thing. If you are able to scan real time data with a scanner or torque app you can watch your LTFT's at idle they should be very close to 0. With the leak in my cold air intake they would be all over the place, and start at 0 and go up to 20 and back down. When they would hit 20 the engine would seem like it was going to stall.

The leak in the intake manifold was really loud and you could easily hear it when the engine was at idle.

Unknown_eyes · November 21, 2020

On 11/1/2020 at 8:26 AM, Firehawk T/A said:

Come to find out I also had a vacuum leak in my cold air intake which was after the MAF. Put the truck in park and let it idle for a few minutes. If it doesn't have a steady idle you have a small leak.

I'm just curious if you've experienced and more CEL's or other issues. I'm thinking of doing this swap on my 2020 Sierra 5.3 and adding the Pulsar lt. I already have a gm cai and Borla S-type installed.

The part numbers I've found are 12639087 for the l86 intake manifold and 12678223 for the throttle body. Are these the parts you used?