Need help getting rid of reduce engine power!

[Optimus Prime]

I have a 2001 Sierra c3,its very similar to the silverada ss with all wheel drive and a 6.0 motor except mine is the lQ4 and not the lQ9.It has a built 408 strocker motor in it with a victor jr. mani and a ls2 90mm throttle body and 75lbs inj..It also has a stage 3 flt trans and a vigi 3000 stall.I had a tuner by me change it to speed density and tune it.but it still didn't work,when i drove it home it was fine but when i drove again it went on again and seems to be turning on more and more,can't go more than 10 min without it turning on.It had a kenne belle on it but took it off to see if that would help fix prob,plus i want to turbo it in future,but still the same outcome.Me and a good friend with more tuning expierance than me hooked up the efilive and it threw the po102 and the po405 while idling,and when i took it for a drive it threw the p1516 code.we did a test and set the p0102 and p0405 to not report and no mil to see if the codes were making the reduce engine come on but it still came on.The base tune it shows right now is from a 5.3,so we even tried a base lQ4 tune and change what it told me to for speed density,and changed the injectors to my old tune that was for the bigger inj.And with that tune it threw p0122,p0405,p0102,and p0443 with the lQ4 tune, and it wouldn't let me give it any throttle,and idled crazy.Thinking about buying a maf and starting over from there.Any help would be gratefully appreciated,havn't got to enjoy the truck for almost a year. thanx RON

[ScarabEpic22]

Hey man, sorry to hear that. I would first check and make sure you have the cylinder volume set properly, it will be completely different for a stock 5.3 vs a 408 stroker and should help you out. I would also recommend starting with a stock LQ4 or LQ9 VE and Spark tables to use as a starting point just so you can get it running and do AutoVE (get a WBO2 if you dont already).

[dfe1]

Does your truck have a cable-driven throttle body or is it electronically controlled? (Both were available in 2002, but I'm not sure about 01s.) From your description, it sounds like it's ETC-- if so, it's a simple fix.

[Optimus Prime]

Thanks for the post Scarab, I will try that.And dfe1 it is etc.I would like to hear more about the simple fix. Thanx again, Ron

[ScarabEpic22]

I think what he means is that you need to full flash a tune with ETC parameters so you dont get the REP light.

[1bar]

Hey Guys, I am optimus primes friend and I am helping him set the truck up.

We first took the truck to a reputable tuner here in Valencia and he tried, but was not able to fix it.

So I told Ron we would start over again and flash it with an LQ4 tune and we did.

Once we did that we got all of the codes Ron listed. The EVAP, and EGR, and Low MAF freq is easy to fix, but the P0122 is confusing me!!!!!

I have a feeling the stock TB has different peramiters or voltages than the stock LS2 and it is throwing it off. Which is causing the REP light.

Is there something in the tune we need to change for running the LS2 TB.

Thanks,
Glenn

[dfe1]

Based on some of the codes you're getting, if the tune is at all close, it may be that some of the problems you're experiencing are related to the engine, not the tune. Regarding the Reduced power issue, I'd guess that the C6101 table-- "ETC Predicted Airflow"-- hasn't been modified appropriately. If you run speed density, and don't modify this table, you'll almost always have reduced power issues. However, it usually sets a P1514 code. Of course if you have 1514 disabled, that code obviously won't set.
Before you do anything else, modify C6101 as shown in the link below--
http://efiforum.iqd.co.nz/showthread.php?t=5029

Then, make sure the value in B0104-- Cylinder Volume-- is accurate. Remember, the value is equal to the volume of a single cylinder and must be consistent with the Data Units you've selected (cc or ci).

If the suggested changes don't get you up and running, post your tun file so we can take a look.

[1bar]

I have spent time adjusting the C6101 table and have even maxed it out as an attempt to keep the truck out of REP. But the REP light just wants to stay on.

I can even reset the code while the truck is running and the REP light goes away, than it will set a P0102 code and than about 20+ seconds later, it will throw the REP light.

I will read that post you have and see what it has to say.

Thanks for all the help,
Glenn

[1bar]

I will try your values for the C6101 table and see what happens.

1. I have P1514 set to 1 trip, emission related. If I set this to non emissions, will it still go into REP?

2. could you give me an example of how to figure cyl volume for the B0104 table.

thanks,
Glenn

[dfe1]

I will try your values for the C6101 table and see what happens.

1. I have P1514 set to 1 trip, emission related. If I set this to non emissions, will it still go into REP?

2. could you give me an example of how to figure cyl volume for the B0104 table.

thanks,
Glenn REP is a safety consideration, it just sets the Check Engine light to notify the driver that something is wrong. The whole reason for reducing power is to prevent the engine from "running away" in the event of an electronic throttle control failure. That's why it's best NOT to take the whole table to maximum values. The key to eliminating REP problems is to simply have all the table values higher than actual air flows. Typically, the most work is needed at lower throttle openings and lower rpm because the stock values in the middle and upper end of the table are somewhat reasonable for mildly modified engines. I had REP issues when I converter to speed density on one vehicle, and after I installed a modified throttle body on another. In both cases, problems were completely eliminated by reworking the 6101 table as shown in the referenced post.

Figure cylinder volume by dividing total displacement by the number of cylinders-- just make sure the units are consistent. If you have a 6-liter V8, multiply by 1000 to convert to ccs, then divide by 8. 6000/8= 750cc per cylinder. If you're working in cubic inches. Just make sure you're working in the same units as is specified in Data Units.

The LS2 throttle body has a 90mm opening, the oroginal truck throttle body has a 78mm opening. You need to let the PCM know about the change.

[1bar]

This is good information. I will try and get to the truck within the next few days and make a few changes.

Here is my other dilema, should I keep working with the old tune or start with the new LQ4 tune. This is what I want to start working with.

What do you think?

Glenn

[dfe1]

Here is my other dilema, should I keep working with the old tune or start with the new LQ4 tune. This is what I want to start working with.
Glenn
Hard to say without looking at the files, but it's probably as long as it is wide. I'd start with whichever file you think will need the least amount of work to get right. Just keep in mind that the file that currently delivers the "best" performance, isn't necessarily the best file to work with. If you've done a lot of rework trying to make something "right" out of something wrong, you may have more to undo.

[Optimus Prime]

Thanks again for all the help,we will be messing with it again soon. we'll let you guys know how it goes. Ron