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If you didn’t buy “auto parts store race truck red” I’ll be disappointed in you.
Overall glad this works 90 sounds cooler than 87mm just saying.
I am huge disappointment, but you already knew that... The 90mm is probably a better unit any way.
At this point, I can not find it, if it does exist... My parts pile probably swallowed it whole.
I have the rare 1 year only 05 trailblazer/early truck style intake with the 90mm opening and it has a 6 pin 87mm TB on it. It looks like an early 3 bolt style 78mm truck intake but has a 4 bolt 90mm opening.
Go get some glitter from the dollar store to mix into the black caliper paint you got. At least then they will be sparkly and potentially attract both small and large mouth bass.
How many acres is your parts pile? I’m assuming it to be nearing the size of the national debt
To add another data point: an oem ls2 silver blade throttle body doesn't open all the way with the 12574221 tac module. At least in my experience. I wanted to get rid of the x link on my 2004 avalanche. Swapped the tac and the harness adapter. The throttle body only opens to about 80 degrees. Swapped the x link and stock tac back on and it opens the full 90. Might try an ls3 throttle body and see what happens as I've already had one x link fail
I ran a 90mm and then a 102mm TB on my 05. I am running the 02 TAC module and an old spear tech adapter that I got like in 2008. No issues. I went this route after I had an x link failure
To add another data point: an oem ls2 silver blade throttle body doesn't open all the way with the 12574221 tac module. At least in my experience. I wanted to get rid of the x link on my 2004 avalanche. Swapped the tac and the harness adapter. The throttle body only opens to about 80 degrees. Swapped the x link and stock tac back on and it opens the full 90. Might try an ls3 throttle body and see what happens as I've already had one x link fail
Are you able to look at the tune? Perhaps the maximum rotation angle was reduced in the tune? My 87mm Hitachi ETB0024 truck throttle body with a 2005 P59 6.0L based tune, that same TAC module and an 8.1L van pedal is too willing to go to 100%. It goes to 100% opening at ~70% pedal. Then again I matched up all the 2002 8.1L stuff, stock PCM calibration in an 0411, the TAC module, the 8.1L pedal and 8.1L TB and it does the same thing. Does not seem to hurt anything, I just wish it was more linear through the full range of the pedal. I have a buddy that uses the GMT400 truck 6.5L Diesel/8.1L in all his LS swaps and he said would let me borrow a new spare he has for testing, I just have not done it yet.
After putting some miles on mine I discovered a small but easily corrected issue. On the sweep test the ETB0024 was setting a DTC for P0220 on about 1 out of 20 startups. I looked at the freeze frame snapshot data. TPS 2 was going ever so slightly out of its allowed voltage range when the TB was fully closed during the sweep test at a TPS reading much lower than the TB ever sees with a running engine. The PCM has Min/Max "Throttle Stop" values that work as a digital stop to prevent the throttle butterfly from smacking into the throttle bore. I slightly increased that stop value TPS angle wise so that the TB would not error out during the self testing. It does not alter the actual running of the engine in any way since the throttle blade is alway open atleast 6-8% when the engine is running.
I was also tuning an Avalanche with a TorqueStorm that kept going into REP because of a calculated air mass error. While I eventually got that logic happy, I found it extremely dangerous to suddenly not even be able to get the thing out of traffic without clearing the code. If mine happens to go into REP now I will atleast be able to get out of traffic. I still limited the power considerably but have it set to allow for more than an idling engine speed. Remember this is a double redundant system thus extremely unlikely to have a failure resulting in loss of pedal control anyway. I have had cable throttles stick before, shift to neutral or push on the clutch and shut down, stuff happens. I find the lack of ability to accelerate due to a calculated air mass error far more dangerous than the slight possibility it ever loses throttle control in normal operation.
Finally I did away with the stupid cruise control tailight resistance logic that was preventing my cruise control from enabling with LED brakelights even though I had all the inputs setup correctly. That resistance test only runs one time per drive cycle at key on and would not prevent an in-flight failure of the cruise control deactivation switches plus the switches are double redundant to start with. So long story short I am not worried about disabling that logic either as it has almost no benifit from being there in the first place as most wiring failures occur from vibration and strain that happens with the engine running while driving.
Ignore the post above! After several hundred miles of working seemingly well the PCM locked itself down, the engine stalled and refused to start. P0606/U0107 codes present. I opened that P59, used the reset pin, reflashed with an older file and got it going again. I put a Genuine GM throttle body on it which works but I also decided to look over the Hitachi unit more for science purposes. Under the cover I found an throttle stop adjustment screw for the closed position. I tried opening it 1 turn. It instantly set P0120, P0220, and P1516 codes. So I went the other direction, at 1 full turn out the butterfly was contacting the bore, at 1/2 turn it did not contact or bind and thus I left the adjustment screw 1/2 turn out from where it was initially. It has not reset P0220 since. It seems the PCM was commanding it closed more than the closed stop setting allowed it to close thus the random P0220 codes.
Can someone verify that their cruise control functions with this setup? It is now the one remaining thing I am chasing on mine. PCM never will set "Cruise Lockout" to "NO" despite the fact I have verified all necessary signals are in place and even swapped tailight bulbs for incadescent.
Jul 3, 2025 | 05:34 PM
The 90mm is probably a better unit any way.
