Hello
I did the 3400 swap in a 98 sunfire and the speedometer is off by 7-8 mph at 65mph. At 65 true speed the speedo reads 73mph. I have a 4t45-e and the VSS has been run to the 05 GAM PCM and the 98 sunfire PCM which has been piggybacked. Is there any way to correct this problem using HP Tunners or a different VSS sensor? The problem has been there since day one of the engine / tranny change.
Thanks for the help.
Jim
no idea man shouldn't have anything to do with the VSS unless your not wired right cause almost every GM lately has been 400 000 pluse per mile doesn't mater what engine or trans it is
never looked to see if HP tuners can do that but i think your the first thats had an issue such as this after a swap
JBO since July 30, 2001
Perhaps the way you have the wires is screwing with the resistance causing the pcm to think you are driving a % slower than you really are? I'm not sure if that even makes sense since I don't know how the vss/pcm interact, but its just a thought I had.
Smaller tires than the donor car will make the speedo read higher.
I had this issue with my Park Ave donor car... much smaller tires on a J-body than a C-body... I used my PowrTuner software to recalibrate the # of pulses per mile in the PCM.
The 400,000 pulses per mile on every GM lately , does that include a 98 sunfire? I could be wrong but I think most people who do this swap use a 5 speed manual. I am using a 4 speed automatic. I am really not sure what the manuals use for the input for the speedometer., I do not believe the manual use a VSS in the tranny? I do believe that John has the right thought if the 98 sunfire use 400,000 pusles like a 05 GAM. The wheels are smaller on the J than the GAM. Next question is there anyone around the Twincities that can Program the PCM using the Powrtuner software? If not I will send the PCM in, any quess at what I shoul tell them to recalibrate the Pulses per mile too. I am using a 195/60/15 tire, i think.
Thank you for the help
Jim
The PPM might be the same, but the computer for different cars is figuring on a different tire size.
Either A) Upgrade to the Grand Am tire size. Or B) You'll have to change the PPM count in HPT (if it will let you) until the speedometer is correct.
i find it amusing that SHOoff has nothing better to do but follow me around & be an unhelpful dick in even cross-forum. - Jon Mick
I would try changing the wheel size with HP tuners and see if that helps. I wouldn't see why it would be off that much. It also could be in the piggyback if the vss is wired through the Sunfire pcm that could throw it off. You can wire the vss into the 3400 pcm and it should read properly. Or try a different flash.
C:\Users\Phillip\Pictures
BTW, it's 4000 ppm... not 400,000.
From what I remember , originally I had the VSS only going to the 3400 PCM and the car ran good but I had no speedo. I them spliced into the VSS and sent it to the J-body computer too. After i did that the Speedo worked but it is just off. It sounds like I can pick tire size on HP tuner, I will try that. Or maybe I will but some taller tires on it. Thank you for the help. I will let you know what I find first, a person in the Twin cities that has HP tuner or taller tires.
Axel wrote:is there anyone around the Twincities that can Program the PCM using the Powrtuner software?
PowrTuner is for the 3800 L67... not sure if it would work on a 3400.
The sunfire pcm is running the speedo am i rite? If so... it's not the computer...
Are you running stock sized tires should be the first question.
It doesn't matter what tire size is programmed in the ga computer if the sunfire computer is running the gauge.
- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs
i forgot to mention, I am running a 4t60e on my swap and have no speedo problems.
- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs
Quiklilcav wrote:The tire sizes on the N-body and J-body are the same. If the 4t45e transmission is hooked to the J-body computer, there is probably a difference in VSS output due to the different FDR. I'm betting if you use the signal from the N-body computer, it will read correctly.
Actually, you're right... (sorta..) the tires on the Alero are 225/50R16 and all of my Z24 J's were 205/55R16. Which makes the overall diameter just about the same... just the width is different. The FDR sounds like a good answer
I was thinking the reluctor ring was on the outside of the diff so the gear ratio didn't matter. Maybe different for automatics.
i find it amusing that SHOoff has nothing better to do but follow me around & be an unhelpful dick in even cross-forum. - Jon Mick
Quiklilcav wrote:SHOoff wrote:I was thinking the reluctor ring was on the outside of the diff so the gear ratio didn't matter. Maybe different for automatics.
I always thought this as well, but it's possible on the newer ones it's not. The difference in FDR ratios between the 4 cylinder 4t40e and the 6 cylinder 4t45e would just about account for the difference in his speedo, so I'm leaning toward it being the case.
But if it pulses 4000 ppm it shouldn't matter about fdr. Do both transmissions use 4000 ppm?
- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs
Quiklilcav wrote:Oedwards wrote:But if it pulses 4000 ppm it shouldn't matter about fdr. Do both transmissions use 4000 ppm?
The speedos all use 4000ppm, but that comes from the ECM's buffered output. Since vehicles differ in FDR and tire sizes, the ECM has to process a raw signal and output the accurate pulse for the speedo.
HAHA, hook your VSS right to the input for the speedometer. It will roll over by 30mph.
i find it amusing that SHOoff has nothing better to do but follow me around & be an unhelpful dick in even cross-forum. - Jon Mick
