L99 / LS3 Fuse Mod. Why Not Try it?

[Gen5SSRS]

After reading the fuse mod threads on resetting the ECM's for the L99, and seeing the improvement. I wondered if the same affect may apply to the LS3? I just completed my pain staking 1500 mile break-in and was working the ECM out of granny mode. After reading the threads I decided to try removing the #5 and #20 fuses for about an hour. I got in and HOLY $#@& here we go!!! We're wide awake now! The car probably would have come around on its own, but no waiting now. I am not suggesting anyone try this, but it worked for me. I'm not saying, I'm just saying. If you're coming out of a break-in period, might be worth a shot.

[Van]

Are you sure it wasn't a sort of placebo effect?

[patriotpa]

I don't see how it could possibly hurt anything, so why not?

[EAkrish]

I wonder if I would benefit from this when I already have a custom tune.....

[Gen5SSRS]

Are you sure it wasn't a sort of placebo effect?

Yep, I didn't time the car, but I know my cars. It definately woke it up. Other threads have reported their cars "waking up", I just shortened the process. Note: I may have gotten the same result by horse beating it a few runs like my 4th gen SS, but I didn't have to on this one. I have rolled on the accelerating a few time over the last 100 miles or so with some what dis-appointing results. I rolled on the accelerator after the reset, and the car threw me right back in the seat like it should. Anyway, like I said. It may not work for anyone elses LS3. But it worked for me. I wouldn't have even tried it if I felt my car was running up to par.

[broncosman]

I'm at 900 miles now... should be ok for me to do it right? (auto 2SS) and start getting on her a LOT more?

[Gen5SSRS]

I would only try this if you're finished with your break-in and unhappy with the power output. The same result could probably be acheived by running the car hard for a few passes. I was more curious to see if resetting the ECM would result in the ability to "quick learn" the driver learning portion of the ECM. That appears to be the Result, soooo, I am happy.

[PQ]

I was hoping mine would wake up after my break in period. Like yourself I went by the book. Literally. Wasn't easy. With every passing Mustang and Bonnies big mouth, it was really hard. When I made it to 1500 I was sorely disapponted. Then after almost 6000 miles, I was at the end of my rope. Good thing I tried this. Again. The evidence speaks for it's self.

Interesting yours is an LS3. There hasn't really been a cry about an LS3 with 'the slows'.

I wonder if it would work in conjunction with a tune?

[DDustiNN]

Originally Posted by Gen5SSRS

After reading the fuse mod threads on resetting the ECM's for the L99, and seeing the improvement. I wondered if the same affect may apply to the LS3? I just completed my pain staking 1500 mile break-in and was working the ECM out of granny mode. After reading the threads I decided to try removing the #5 and #20 fuses for about an hour. I got in and HOLY $#@& here we go!!! We're wide awake now! The car probably would have come around on its own, but no waiting now. I am not suggesting anyone try this, but it worked for me. I'm not saying, I'm just saying. If you're coming out of a break-in period, might be worth a shot.

Hmm, interesting...

[JTinFL]

What exactly do the fuses control? We should dyno it!!

[LS 1st gen]

I don't know that pulling a couple of fuses really qualifies as a "mod" but it could be a worth a shot. As far as I have read here, the only reason this is working is that for some reason the PCM's are not properly switching between the low an high octane tables, so really we're just compensating for that.

All that being said, I think I'll pull some fuses overnight

[EAkrish]

I am wondering if it will work with a tune also pq. I guess I can try it and let everyone know.....

[PQ]

Originally Posted by EAkrish

I am wondering if it will work with a tune also pq. I guess I can try it and let everyone know.....

How was yours running before you got it tuned? If it was running good you may not notice it anyway. If not, it would be cool to see you get an even bigger boost.

[EAkrish]

Mine was running real good b4 the tune and amazing after the tune. I also did my tb porting b4 I got the tune. Just amazing! I might not even mess with it. I don't want to lose the tune, if that's even possible?

[gtbaldini]

If you have a custom tune and are happy I wouldn't try this. It may reset the computer and your out a custom tune.

[radz28]

Originally Posted by EAkrish

I am wondering if it will work with a tune also pq. I guess I can try it and let everyone know.....

It'd seem to me that the tune might already compansate for this I'm sure it wouldn't hurt to try though.

Originally Posted by EAkrish

Mine was running real good b4 the tune and amazing after the tune. I also did my tb porting b4 I got the tune. Just amazing! I might not even mess with it. I don't want to lose the tune, if that's even possible?

I can't speak for the new PCMs, but the ones that were used with the LS1 cars wouldn't simply default to the OEM tune, because it's my understanding one is actually writing over the OEM tune and the PCM doesn't know the otherwise. I'd disconnect my battery for nights at a time and plug it back in and it was still fine. I'd remove PCM fuses and it was still fine. (FWIW - I could tell the custom tune was in there because I had my idle RPM raised from like 550 to 750, because of my converter, and it remained the same before and after.) That's just what happened to me though, and that wasn't with the current model PCMs...

Originally Posted by gtbaldini

If you have a custom tune and are happy I wouldn't try this. It may reset the computer and your out a custom tune.

See above...

[monza66mo]

All the buzz about this so I figured why not try it. I pulled mine last night. No change in my car at all this morning. None. Zero. Zip. Nada. My L99 launched like a rocket from day one so I didn't expect anything.

[radz28]

Originally Posted by monza66mo

All the buzz about this so I figured why not try it. I pulled mine last night. No change in my car at all. None. Zero. Zip. Nada. But my L99 launched like a rocket from day one so I didn't expect anything.

Too bad, but if there weren't complaints before, there's no loss.

Thanks for sharing

[Camar0wn3d]

I tuned in HPTuners on my LS1 and if it is the same for an L99/LS3, this is what happens when you pull the fuses:

There are two tables values used for spark timing - high octane table and low octane table. If you use 93 octane from day one, your computer is using spark timing from the high octane table. If you got a tank of 87 from the dealer, the engine experienced premature detonation and the knock sensors went crazy, and told the computer to use the low octane timing table. What is supposed to happen is after a while of not seeing detonation from the knock sensors, the computer (ECU)tries the high octane spark timing table again. (This doesn't appear to be happening - THIS IS THE PROBLEM!!!!).

The values in the high octane and low octane tables are NON-VOLATILE MEMORY (meaning they are there even if you lose power -like when you do the fuse pull). These tables are usually adjusted when you get a custom tune, and burned into the non-volatile memory. So therefore if you get a custom tune YOU WILL NOT LOSE THESE "TUNED" VALUES with the fuse pull.

What WILL happen with the fuse pull is your volatile memory will be reset. This includes long term + short term fuel trims, knock retard, etc... but what is important in this case is the little parameter that determines which spark table to use will reset...meaning if you were running from the low octane tables before (safe + slow mode), after the fuse pull it will force the computer to try the high octane table again (super giggle fun happy rockin' mode).

However it is important to note that you shouldn't need to try the fuse pull if you've only used high octane gas since getting a custom tune, because burning the tune to the ECU resets all volatile memory. This is why it will go through the idle re-learn process and may run a little weird for the first 20 minutes or so after burning a tune or pulling the fuses.

Pulling the fuses is no different from recovering from a dead battery. The only reason I could see that it would be a problem to pull the fuses is if GM wanted to run diagnostics on the cars with the problem and needed to see the volatile values.

[2010 2-Tone]

Originally Posted by wh0rsep0wer

I tuned in HPTuners on my LS1 and if it is the same for an LS3, this is what happens when you pull the fuses:

There are two tables values used for spark timing - high octane table and low octane table. If you use 93 octane from day one, your computer is using spark timing from the high octane table. If you got a tank of 87 from the dealer, the engine experienced premature detonation and the knock sensors went crazy, and told the computer to use the low octane timing table. What is supposed to happen is after a while of not seeing detonation from the knock sensors, the computer (ECU)tries the high octane spark timing table again. (This doesn't appear to be happening - THIS IS THE PROBLEM!!!!).

The values in the high octane and low octane tables are NON-VOLATILE MEMORY (meaning they are there even if you lose power -like when you do the fuse pull). These tables are usually adjusted when you get a custom tune, and burned into the non-volatile memory. So therefore if you get a custom tune YOU WILL NOT LOSE THESE "TUNED" VALUES with the fuse pull.

What WILL happen with the fuse pull is your volatile memory will be reset. This includes long term + short term fuel trims, knock retard, etc... but what is important in this case is the little parameter that determines which spark table to use will reset...meaning if you were running from the low octane tables before (safe + slow mode), after the fuse pull it will force the computer to try the high octane table again (super giggle fun happy rockin' mode).

However it is important to note that you shouldn't need to try the fuse pull if you've only used high octane gas since getting a custom tune, because burning the tune to the ECU resets all volatile memory. This is why it will go through the idle re-learn process and may run a little weird for the first 20 minutes or so after burning a tune or pulling the fuses.

Pulling the fuses is no different from recovering from a dead battery. The only reason I could see that it would be a problem to pull the fuses is if GM wanted to run diagnostics on the cars with the problem and needed to see the volatile values.

Nice Read!!!!

[SSOOCH]

If you use 91 octane (it's the highest available in my area) will the computer use the high octane tables? Anybody?

[thecamaroguy]

Originally Posted by wh0rsep0wer

I tuned in HPTuners on my LS1 and if it is the same for an L99/LS3, this is what happens when you pull the fuses:

There are two tables values used for spark timing - high octane table and low octane table. If you use 93 octane from day one, your computer is using spark timing from the high octane table. If you got a tank of 87 from the dealer, the engine experienced premature detonation and the knock sensors went crazy, and told the computer to use the low octane timing table. What is supposed to happen is after a while of not seeing detonation from the knock sensors, the computer (ECU)tries the high octane spark timing table again. (This doesn't appear to be happening - THIS IS THE PROBLEM!!!!).

The values in the high octane and low octane tables are NON-VOLATILE MEMORY (meaning they are there even if you lose power -like when you do the fuse pull). These tables are usually adjusted when you get a custom tune, and burned into the non-volatile memory. So therefore if you get a custom tune YOU WILL NOT LOSE THESE "TUNED" VALUES with the fuse pull.

What WILL happen with the fuse pull is your volatile memory will be reset. This includes long term + short term fuel trims, knock retard, etc... but what is important in this case is the little parameter that determines which spark table to use will reset...meaning if you were running from the low octane tables before (safe + slow mode), after the fuse pull it will force the computer to try the high octane table again (super giggle fun happy rockin' mode).

However it is important to note that you shouldn't need to try the fuse pull if you've only used high octane gas since getting a custom tune, because burning the tune to the ECU resets all volatile memory. This is why it will go through the idle re-learn process and may run a little weird for the first 20 minutes or so after burning a tune or pulling the fuses.

Pulling the fuses is no different from recovering from a dead battery. The only reason I could see that it would be a problem to pull the fuses is if GM wanted to run diagnostics on the cars with the problem and needed to see the volatile values.

Awesome read! Thanks. This clears things up very nicely!

[gpr]

You only have 91 octane because you live in a higher elevation. the same is true for where i live. You don't need the higher octane at higher elevations. I am gonna go further on this speculation, as i believe what wh0rsep0wer said is correct and the cause for the cars to run better, but since no one has logged data from before and after the fuse pull....

Some are saying they have filled up with premium (91 or 93) gas since day one. Well if you got old gas that wasn't up to standards with the high compression of these engines it will easily cause the engine to knock thus kicking you into the low octane spark table, even though you have filled with premium since day one. Always fill up from a good fuel source that gets fresh fuel often, as it doesn't take long for gas to go bad.

[GTAHVIT]

Originally Posted by broncosman

I'm at 900 miles now... should be ok for me to do it right? (auto 2SS) and start getting on her a LOT more?

From what we can tell, Yes.

Obviously this isn't a GM approved thing. But there shouldn't be any real risk.

FWIW.

[GMRULZ]

Originally Posted by gpr

, but since no one has logged data from before and after the fuse pull....

.

I have dynoed mine before fuse pull 319rwhp 2 pulls back to back, and after fuse pull w/ in 5 minutes of the other 2 runs and picked up 8rwhp, 327rwhp.