2001 Galant speedometer wiring schematic help please..

[redwing52]

I'm wondering if someone could help me. I have gone as far as I know with the use of the internet only. My Galant has no speedometer only. Tach works, The odometer is lit but never changes. (obviously) I can't read MPH with my scanner at the PCM. It sets a code for no VSS and I tested the VSS and it tests fine. 4 pulses per revolution. I think if someone could help me with a schematic that showed from the VSS to the speedo, PCM etc. it would be a huge help. I can't seem to find any place where I can get a schematic online. I'm helping a friend and hate to spend tons of money on a one time deal buying a service manual. If you could help me I would be very grateful. Thank you in advance. :)

[juicejax]

Subbed hopefully someone can help you...as it would help me as well....I have exact same problems

[redwing52]

Juice,
Did you by chance mess with your radio about the time the problem came? I've found other posts that had that in common and my friend just put in a fancy radio/amp.

[juicejax]

Juice,
Did you by chance mess with your radio about the time the problem came? I've found other posts that had that in common and my friend just put in a fancy radio/amp.
Yep, that's what caused the problem....when I bought the car the radio was removed and harness was cut and each wire individually taped....so I went to a audio shop and had them look at it so I could set an appointment for later... when the guy got in the car first thing he did was remove the tape from the harness looked at it and told me he could fix it. So I go to leave with the wires sitting inside the space behind where the radio is suppose to be but they are not taped up... they eventually touch some metal back there....then a loud noise happened..then speedo jumped all the way up and landed on 0...hasn't moved since

[juicejax]

I also know that there is a wire in the factory radio harness that isn't suppose to be connected...its yellow/blk it's actually the vss wire...for head units that came with Navi systems

[redwing52]

I'm starting to not like the sound of this. As I searched the internet I did stumble on people who had issues with radio wiring and lost there speedometer function. Seems they lost some function of the PCM. All parts of the PCM worked fine with the exception of the speedometer output. One I read about bought a new PCM thinking he had the shorting issue repaired, but still had the issue. He therefore destroyed the new one. I can't think of any time in my life that I had such an issue with so little info available and I have been a mechanic for almost 40 years. I'm stumped. I see the oem electrical manuals are over $300 and I still wonder if the info needed is going to be covered. Lots of people struggling with this issue and it seems no one really has a good answer.

[juicejax]

I'm starting to not like the sound of this. As I searched the internet I did stumble on people who had issues with radio wiring and lost there speedometer function. Seems they lost some function of the PCM. All parts of the PCM worked fine with the exception of the speedometer output. One I read about bought a new PCM thinking he had the shorting issue repaired, but still had the issue. He therefore destroyed the new one. I can't think of any time in my life that I had such an issue with so little info available and I have been a mechanic for almost 40 years. I'm stumped. I see the oem electrical manuals are over $300 and I still wonder if the info needed is going to be covered. Lots of people struggling with this issue and it seems no one really has a good answer.
Ya it sucks...I miss my cruise control more than anything....hopefully you find something out. Please report back here if you do...40 years? You can do it!

[redwing52]

40 years of experience is not worth much without the knowledge. They are all similar but have the own idiosyncrasies. If I get it figured I will post it here and everywhere I can think of. I am leaning toward this. It seems that there is a signal that goes from the vehicle speed sensor to the PCM computer. The PCM interprets that signal and send out a serial comminiction signal to the cruise, radio and speedo. It seems (maybe) if that signal (like at the radio) gets short to ground or shorted to hot (12 volts) one part of the PCM will fail. All other functions work fine but the speedo, radio,and cruise output is dead. I would sure love some info. Pinouts for the speedo etc. Seems no one likes us. :icon_biggrin:

[redwing52]

Can anyone even help me with a little info. Do you know what voltage I would get if I back probe the output from the VSS sensor with all plus together and the wheels spinning?

[juicejax]

Wish I could help....I suck at all things cars other than tires lol

[redwing52]

Juice, hang in there. We'll either get it figured out or at least we will be lost together. Kind of like we are now. :)

[redwing52]

Hey Juice,
I did find a little bit more info. God Bless the internet. I won't be doing anything during the holiday weekend but I will keep you up to speed if/when I get anything figured out.

[juicejax]

Good to hear!

[redwing52]

Hi Juice,
I got mine fixed. The speedo was shorted to ground by the radio wiring. I have learned some about how it works and maybe I can walk you through some of the things I did. I'm a little concerned that you might not have some of the tools that you might need. Do you have a volt ohm meter? Basic set of small metric sockets etc? If you want to take a stab at it you can buy a meter very inexpensive at Harbor Freight. Check your personal messages (email) at this site.

[juicejax]

Thanks...ill message you later tonight