Ok, so after getting the thing all tweaked to actually run, why does the speedo stop working when he does a full throttle run as soon as the stabilitrak kicks in? (we didn't try with the stabilitrak disabled). The speedo starts working again as soon as he lets off.
I initially thought the speedo source was gm lan instead of calibration...then I found that the PCM doesn't even have that setting available.
Any thoughts?
Last edited by BBA; 10-13-2007 at 04:42 PM.
I also have an 06 TBSS and that also happened to me when i installed the converter...i asked a few questions here a while back to see if there was a fix and they told me that there wasnt anything i could do...hope to find a solution...
BBA, I suspect that the engine RPM vs input shaft speed or something similar gets out of range and cant do calculations. Common to all stalls on these things.
Makes you wonder where they are pulling MPH from.
You can shut stabilitrak off completely and it will still do it.
Are you saying yours worked when you isntalled the converter and it dropped out after tuning?
Its annoying as heck to me. I got on the interstate the other day and did a full throttle run up to I am GUESSING 80MPH. I let off to cruise throttle position and still no MPH. Had to let way off for it to pop back in and then was OK.
It's Matt's (Atlas) TBSS. I think it started as soon as he put the stall in. My thoughts are it can't handle the error in converter slippage.
There has to be a way to hack it to only read output shaft sped for speedo calculation, that or the speedo can't keep up with the increased accelleration and goes into a default error mode. Do the supercharged guys whithout stalls have the same problem?
This happened to me after I installed the converter. I know of many others it happened to after installing the converter and no one has found a fix.
The reason I asked if supercharged guys with stock stalls are experiencing the same problem is to find the culprit. It's either speedo performance or it's input/output shaft slippage, which means the BCM probably has some sort of threshold for setting an error in the speedo.
I thinkt it's about time HP Tuners does an update to read and program GM BCMs.
Well, the stall will have a major effect on rpm vs input shaft speed during hard accel, but will not change the relationship of inputshaft vs output shaft in a given gear. Does indeed make u wonder where they get the speedo from, sensor-wise. Would also be interesting just how much more stall than stock u can get away with and not have this issue. My bet is not much.
06 Z06 ETP heads, 244/256 hyd. roller, crower stainless shaft rockers, Kooks stepped race headers,elec. w/p, 160 stat, vararam, ram dual disk, ported intake and t-body, 100 shot spray until the 441 goes togetherhttp://www.youtube.com/watch?v=fm1hrBcq63U
2016 Callaway Z06 a8 3lz zo7
Heads, cam, headers, 2.3L s/c, 9.5 lower/2.625upper, meth, 103mm t-body,
Stock high and low fuel system for now (I know right?)
Yea, I dont think you can get away with much. I think I have read about guys with custom 2500 stalls having issues.Originally Posted by 9secZO6
Normally you think they would calculate MPH on rear shaft speed. Dont have to worry about what gear or anything.
But it appears they are doing something stupid like calculating MPH based on RPM and gear.
Dunno. Wish someone would figure it out. Would like my WOT speedo working again.
Glad u said that 'cause I did not wanna look stupid myself(but I for damn sure thought it)
06 Z06 ETP heads, 244/256 hyd. roller, crower stainless shaft rockers, Kooks stepped race headers,elec. w/p, 160 stat, vararam, ram dual disk, ported intake and t-body, 100 shot spray until the 441 goes together
2016 Callaway Z06 a8 3lz zo7
Heads, cam, headers, 2.3L s/c, 9.5 lower/2.625upper, meth, 103mm t-body,
Stock high and low fuel system for now (I know right?)
I'm pretty sure the speedo still works when the car is in neutral (or drive if you stall out) and engine off - this throws out the rpm and gear theory. The important thing is that it does know the true speed... otherwise it wouldn't shift.. or add miles.. I can deal with it not adding miles tho! Would make every stoplight worth the WOT.
I remember I did get a TCM comm error after doing this.. Perhaps the TCM loses comm with the rest of the vehicle and calculates shifts based on mph. You could set the WOT shift rpm to something noticably low on the 2-3 (like 4.5K) and see if it ignores this and shifts only at the commanded mph.. You'd obviously need to do this from a stop.
2006 Trailblazer SS - Stalled, Cammed, Tuned, Turbo'd, Built, and Stroked.
Runs on cash, blood, sweat, and tears...... and 93 octane.
2007 Cadillac STS-V - Stock.
I dont think so because when I lose my speedo under WOT I still have the PIDS for input speed, output speed and I think I have accurate TC slip PID.
I'm betting it's in the BCM.
Do 2007 TBSS's have the same problem?
Probably right. Something is out of the normal tables and cant calculate.
Yes 07's same issue.
Anyone know how to fix this yet? This thread shows someone figured it out?
http://www.trailblazerss.com/forums/...showtopic=8638
Maybe, I don't know what else other people have came up with, but there are a few things in the TCM that efilive shows that we can't see. A few are codes that look promising, but the TB I've been working with shit out the tranny and has been able to try out my changes yet. I ran across them hacking the TCM binary trying to find the missing tables that control TCC lockup under WOT. I think I found them too, but again he hasn't tried them to verify.
Last edited by Bluecat; 12-12-2007 at 09:14 PM.
They got the TCC working in second but they have not fixed the speedo problem.
I think it's in the BCM.
You are the man. Find anything on the part throttle TCC 2nd gear? That table does not respond to anything.. tcc lock in 2nd commanded in scanner obviously does..
What is your setup for reading the tcm's 'raw data'... I suppose reading the data isn't as complicated as writing? I need to learn more about this.
2006 Trailblazer SS - Stalled, Cammed, Tuned, Turbo'd, Built, and Stroked.
Runs on cash, blood, sweat, and tears...... and 93 octane.
2007 Cadillac STS-V - Stock.
EFILive keeps the pcm and tcm in different files. The guy who actually owns the TBSS got somebody to take the EFILive file and converted it to a bin and send it to me. EFIlive will still read the bin back in, so after I make manual changes to the file he can just flash the tcm like normal. (The owner has both HPT and EFILive)
Here is a question...if you fix it with EFI Live, and then do a read entire in HPT, will the code be saved in the HPT file, even though HPT may not have a gui interface table for it?
Yes. The change would carry, you just couldn't see it. The one I'm hoping is doing it is 731 - incorrect gear ratio 1st gear. Its turned on, but dosen't enable the mil. So you'd never know it was throwing by the light. There is a code for every other other gear 2nd, 3rd, ect.. but they are all turned off. The tune I've been wanting him to try has that turned off, including about 6 other codes that are relative to the vss or input/output corrilation. Hope that kills the speedo bug. LT1 cars were the same way with big stalls, the speedo keeps working but the tranny would go into limp home mode. Killing all the VSS relavent codes fixes the problem on them, so what the hell its worth a try.
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