GA95DCMSS

iTrader: (13)

I'm currently running a LQ4 with a cable throttle body in my 1995 Impala SS. I'm also using a gauge cluster out of a 1995 Chevy Camaro. Since I've done my swap, my speedometer is showing 2.5x what my actual speed is (verified via HPTuners and GPS). I emailed HPTuners about this, and the answers they provided didn't really assist in solving the problem. As these engines are becoming more and more plentiful, I took it upon myself to find out why my speedometer is reading so high, so others wouldn't have the same problem.

I decided to toy around with the EFILive Demo and see what I could find. While digging around in the Speedo tables in EFILive, I found out some very interesting Information, and the cause of my speedometer reading higher than what it should. There is a setting under Speedometer, that says PCM Primary Pulses per KM output Rate: It states this is what the PCM outputs for J2 Pin 50 for the PCM, which is one hooked to my speedo. This controls what output rate (4000ppm which is actually 3999.22) the PCM uses for the cluster and cruise control.

Looking at the 2004 GTO A4 tune in EFIlive, it shows the PCM Primary pulses/KM output as 6226;



but yet in a 2004-05 CTS-V it shows it as 2485;


as it does a 2000 Silverado A4, 2002 Corvette Z06, 05 Silverado, and so on. A difference of about 2.505x, which would explain why the speedometer reads so high. I guess the GTOs were the GM oddballs when it came to PPM outputs. The only way I have found to fix this is to find a tuner with EFILive and have them change the parameter, as HPTuners doesn't have this feature. Some associates and I have emailed HPTuners support to try and get them to add this to the next release, but only time will tell how that works out.

I have yet to fix mine, because I use HPTuners, so I need to find a Tuner willing to flash my tune to a PCM with HPtuners, change it with EFILive, and read it again with HPTuners. Oh joy

snoopy1

thank you. you just totally answered my question, although my actual info search was to find out if the ppm output to the speedo could be changed although i want to change mine to 16000 ppm to avoid the need to purchase an additional adapter for my aftermarket speedo.

info is power.......

downset71

I had the same issues with my 04 gto motor in my monte. Went back and forth with John at Speartech, he did my GM harness and Ecm programming. I am using an autometer speedo. Had to settle for a dakota digital box to convert pulses. Aftermarket guage is more forgiving because u can just do a 2 mile run and hit button and it will self calibrate

SMOKINV8

iTrader: (6)

Thanks for bumping this... Looks like I need to find out if HPT supports adjusting the speedo output yet.

GA95DCMSS

iTrader: (13)

No problem guys, I'm glad it finally helped someone. HPTuners does support adjusting the PPM now, you just have to email support and have them send you the latest beta. It'll be under the speedometer tab (of course).

aknovaman

iTrader: (7)

Or just find someone with obd2 tunercat and they can adjust anything.

GA95DCMSS

iTrader: (13)

That works too Anthony. I need to find a copy of that, I need to make an AC adjustment in my OS.

aknovaman

iTrader: (7)

Email me the settings you need changed along with your file.

SMOKINV8

iTrader: (6)

Latest beta? Kind of ironic, but I think mine is a couple months old. Thanks again for the info, might make dialing in an aftermarket speedometer a little easier.

69 Ghost

Calibrating the aftermarket gauges are one thing but you still need to get the OS set up correctly. As far as I remember the pulses on the 04 GTO are 4000 but I will have to go back an check. If you are running an automatic trans you will need to fix the calibration or it will be off on the shifting. When I calibrated my speedo I used my iPhone to go 2 miles. My pulses were off by 1 when it said 2 miles. I believe if you guys go into the tools there is a conversion routine that will set the shift parameters, etc for all 3 tuning tools. TC was spot on for me.

MillsMotorvation

Well mine is reading to low, HP Tunes dont seem to have a answer. I have a 8000 PPM Dakota Digital, but sit reads really low! What can I do?

GA95DCMSS

iTrader: (13)

As listed above, the pulses for the 2004 GTO are NOT 4000 ppm. If it was, I would have never had to go and do this. I am running an automatic trans, and I verified my speed off my GPS. At 35mph, it showed I was doing around 80 on the speedo IIRC. If your OS isnt programmed to output the correct PPM from the PCM, then calibrating your aftermarket speedo would be damn near futile. Most aftermarket speedos I've dealt with have an option for what ppm to use.

downset71

running a 700r4. my OS dont care-