PCM tune...how do I know if my TB has had one or not?

[Sib]

Hey guys,

I have been looking on here for a minute about getting my pcm tuned from either pcmofnc or pcm4less. I thought I read somewhere though that if you are in park and step on gas and your rpm's go over 3000 then your pcm has been tuned?

So...first, is that true or did I just sort of make that up in my head?

Second, if not true, is there another to tell if my pcm has been tuned or not? I have not driven in a trailblazer before buying mine so I have no idea what the difference would even feel like if it was or wasn't tuned.

BTW, I have an 08 TB LT. Got it from a stealership and it had one owner before me and I don't know anything about the previous owner, so not sure if they were enough of an enthusiast to tune the pcm.

Thanks in advance!

-Matt

 

[djthumper]

It is really hard to say if you can easily tell if it has been tuned. Unless of course you have the equipment to ready your PCM. I would be willing to bet that if there are not very many mods on it that you don't have a tune.

 

[RayGumm]

Mine has no rev limiter that I'm aware of (was scared to take it past 4k rpm) yet I am almost positive it does not have a tune. I can tell it has 'torque management' because because the throttle body does not open WOT on command.. it takes a good 2.5 seconds to open WOT after the pedal is floored. So the Rev limiter thing may not be true for 06 (mine) plus vehicles.. any other insight out there?

 

[Sib]

Yeah there are no other mods. What reader would be able to tell me if it was tuned?

 

[djthumper]

You need someone with a techII or an HPtuner something in that realm.

 

[kickass audio]

The biggest thing I can say to see if you have a tune or not is to judge how firm the shifts are on the transmission and how likely you are to chirp your tires if you stomp on the gas. My truck can only get the tires to break free for a fraction of a second and that is rare to have happen. The shifts are usually firmer and make you feel more of a buck in your seat when changing gears if the user changed shift firmness. There are so many things you can tweak with a tune that it's hard to say for sure if yours was done or not. More than likely not. My truck was never done but I did have all of the computer systems on the truck flashed with the latest firmware at my local shop and it seemed to have helped with the shift firmness and throttle response over the old firmware it had. I can't complain about that at all.

 

[dmanns67]

If you can afford the downtime, ship your PCM to PCMofNC and have them check if you have a tune or not.

If not, no big deal. They will have your PCM in hand, so might as well get it tuned. You are wanting a tune anyways, two birds with one stone.

Since you have a 2008 TB, you will have to send them your TCM as well.

Try emailing or calling Kelly at PCMofNC. She might be able to give you more info on determining if you have a tune or not. Like Larry said, might need to find someone with HP Tuners if sending off your PCM is not an option.

 

[KNBlazer]

You could use a scanner and read the PCMs CAL IDs, I think aftermarket are different from those of GMs factory... anyone who knows for sure can confirm this...

 

[limequat]

You could use a scanner and read the PCMs CAL IDs, I think aftermarket are different from those of GMs factory... anyone who knows for sure can confirm this...

Nope, cal ids are not changed during a tune.

Because there's so many things that could be done or not done, there's no good way to tell if a truck is tuned or not. You could test the speed limiter (usually about 98 mph) as that's often the first thing to go, but I've had customers ask me to leave that intact while -say- the shift points are changed.

When I do a mail-in tune, I always mark the invoice number and put a Lime-Swap sticker on it. But if it's done in person, there's probably no external indication.

 

[AbsoluteZero]

Wonder how the dealership detects "altered calibrations"? There numerous service bulletins telling the dealers to check for pcm alterations and deny warranty if found.

 

[AtlWrk]

There was something GM required dealers to check before warrantying drivetrain repairs... can't seem to find it now.

EDIT: Gah! Beat me by mere seconds AbsoluteZero

 

[Sib]

The warranty issue would be good to know. Didn't
Even think about that. I just got the TB a little
Over a year ago and I still have warranty for my engine and drivetrain.

If that is the case I will just wait until warranty
Is up then jump in to the pcmtune.

 

[KNBlazer]

There was something GM required dealers to check before warrantying drivetrain repairs... can't seem to find it now.

EDIT: Gah! Beat me by mere seconds AbsoluteZero

I remember there was a thread about Corvettes and warranty issues involving tunes... thought for sure the CAL ids were different from stock....

 

[KNBlazer]

I think this is the thread I was basing my assumption on, in this thread it says it's the CVNs that are tracked... Of course I have no personal knowledge, this person claims their warranty was voided based on this info....

Limequat, is this true?

Kept reading and it's mixed whether in fact a simple scanner can pick up the tune.... :blink:

http://www.corvetteforum.com/forums/c7-tech-performance/3397328-can-gm-detect-aftermarket-tunes.html

 

[Mark@PCMofNC]

Hey guys,

I have been looking on here for a minute about getting my pcm tuned from either pcmofnc or pcm4less. I thought I read somewhere though that if you are in park and step on gas and your rpm's go over 3000 then your pcm has been tuned?

This isn't something we change (or even have the ability to change as far as I know).

PM me your VIN number and I can search our database to see if it matches a past customer of ours.

Knocking on wood, we've never heard any of our customers being denied a warranty due to tuning.

 

[Mounce]

Nope, cal ids are not changed during a tune.

Because there's so many things that could be done or not done, there's no good way to tell if a truck is tuned or not. You could test the speed limiter (usually about 98 mph) as that's often the first thing to go, but I've had customers ask me to leave that intact while -say- the shift points are changed.

When I do a mail-in tune, I always mark the invoice number and put a Lime-Swap sticker on it. But if it's done in person, there's probably no external indication.

What models did the 98mph speed limiter affect? I've seen this discussed a handful of times before and I, as well as many others, have been over 100mph with no tune.

-sorry for going off topic, just never had a chance to ask one of the guys that do tunes.

 

[Sib]

Ok so first of all, just want to say thanks for all the feedback. I have never been a part of any forums before, and everyone's info here is just saaweeeeet! Y'all are awesome.

Second, I see that dmann said if I send my PCM in for a tune, I also need to send in my TCM. Where is the TCM located? Anyone have any pics of it?

I am not much of a car guy, but I have learned more in the last few months (joined here in September) about cars than I have the rest of my life. I was always playing sports (played baseball in college) so growing up that took up most of my time and never did anything on any car except put a new head unit in. So again...thanks for all the feedback. Hope my questions don't sound too much like a noob!

 

[Mounce]

Noob questions are welcome, you've gotta learn somewhere.

Try googling trailblazer tcm location and see what comes up, look at images and you should see it and where it's at.

 

[Mark@PCMofNC]

The TCM should be located with the ECM, they're usually in the engine bay back-to-back. It'll have one connector plugged into it, and be about 4x4x1" in size. Your ECM will look slightly different, but this is what the TCM looks like:

 

[Sib]

Thanks. I will be calling soon just to get some pricing. Might not be able to do until after the holidays as my money is going to have to be spent on other people. The life of a family man.

 

[mcsteven]

What models did the 98mph speed limiter affect? I've seen this discussed a handful of times before and I, as well as many others, have been over 100mph with no tune.

-sorry for going off topic, just never had a chance to ask one of the guys that do tunes.

Interested in this and a few other things as well (like determining if there is a tune without having to plug in the HPtuner). I have an 06 Envoy SLT (swb, I6) that has been over 100 MPH and there have been times where it has chirped second gear. Not sure if it has been tuned or if it is just a strong truck. The previous owner didn't appear to do any other mods other than the clear side mirror turn signals.

 

[limequat]

I think this is the thread I was basing my assumption on, in this thread it says it's the CVNs that are tracked... Of course I have no personal knowledge, this person claims their warranty was voided based on this info....

Limequat, is this true?

Kept reading and it's mixed whether in fact a simple scanner can pick up the tune.... :blink:

http://www.corvetteforum.com/forums/c7-tech-performance/3397328-can-gm-detect-aftermarket-tunes.html

Not sure what a "CVN" is, could be GM jargon. The poster on the 'vette forum refers to it as a "CVN Checksum". I was going to post that if GM was going to check modifications, they would make sure the checksums are correct.
For those that are not software engineers, checksums add up the values of every byte in memory and compare it a known value. It's meant to make sure memory hasn't been corrupted, but would be equally adept at making sure memory wasn't intentionally modified. It would be as simple as comparing the checksum against the released calibration against the checksums in the PCM.

 

[limequat]

Interested in this and a few other things as well (like determining if there is a tune without having to plug in the HPtuner). I have an 06 Envoy SLT (swb, I6) that has been over 100 MPH and there have been times where it has chirped second gear. Not sure if it has been tuned or if it is just a strong truck. The previous owner didn't appear to do any other mods other than the clear side mirror turn signals.

HPTuners and EFIlive are the only ones that I know of for the 2006. Not sure what Trifecta uses.

I wouldn't put a lot of stock into chirping 2nd gear. There's gonna be a large difference in the way a truck with 3.42 gears feels vs 4:10.

 

[Canary2323]

I just emailed pcmofnc and they told me my tbss was tuned prior to me buying it. Send it to my email

 

[The Neens]

Hey guys,

I have been looking on here for a minute about getting my pcm tuned from either pcmofnc or pcm4less. I thought I read somewhere though that if you are in park and step on gas and your rpm's go over 3000 then your pcm has been tuned?

Mine has no rev limiter that I'm aware of (was scared to take it past 4k rpm) yet I am almost positive it does not have a tune. I can tell it has 'torque management' because because the throttle body does not open WOT on command.. it takes a good 2.5 seconds to open WOT after the pedal is floored. So the Rev limiter thing may not be true for 06 (mine) plus vehicles.. any other insight out there?

What models did the 98mph speed limiter affect? I've seen this discussed a handful of times before and I, as well as many others, have been over 100mph with no tune.

-sorry for going off topic, just never had a chance to ask one of the guys that do tunes.

EFI Live parameter B0920 shows factory '02 speed limit at 106 MPH...B1207 shows RPM limit in Park/Neutral at 5100...I don't have access to a '06 or newer for comparison...

 

[kickass audio]

Only thing I have to say about the RPM limit is that on my truck, it is only valid when the truck is not in motion. If I have the truck moving with the speedometer showing a reading and throw it in N, I can red-line the engine. So if someone were to check that out they need to be still and try to rev it up. I also think it may be 4100 rpm, as when I am in park or neutral and rev the engine up, the highest it gets is around 4100 when the engine is hot. If it is cool it will get to about 3800.

 

[BC backroader]

Mine maxed out at 4100 on the highway in top gear, which just happens to coincide with 160 km/hr, or 100 mph. Obviously, I don't have a PCM tune. Does SuperChips make a tuner for our platform? I have one for my K3500, and like it a lot.

 

[The Neens]

Only thing I have to say about the RPM limit is that on my truck, it is only valid when the truck is not in motion. If I have the truck moving with the speedometer showing a reading and throw it in N, I can red-line the engine.

At 50 MPH, mine will gradually climb to 5400 in neutral...