Speedometer help
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LoveMyBeretta
- Registered User
- Posts: 7
- Joined: Wed Apr 13, 2011 6:55 pm
Speedometer help
Well it's like this.
My speedometer WILL NOT work at all. It just stays still or just starts bouncing from 0 - 120MPH and go past 120 then go back to 0. Everything else works. The speedometer is just messed up.
What could be the problem?
- I've changed the speed sensor.
- I've even put a whole new speedometer cluster and the same thing happened.
Am I missing something important? Please anyone help me, and thank you.
Vehicle Specs (if needed)
- V4 2.0 L
- 88' Base Beretta
My speedometer WILL NOT work at all. It just stays still or just starts bouncing from 0 - 120MPH and go past 120 then go back to 0. Everything else works. The speedometer is just messed up.
What could be the problem?
- I've changed the speed sensor.
- I've even put a whole new speedometer cluster and the same thing happened.
Am I missing something important? Please anyone help me, and thank you.
Vehicle Specs (if needed)
- V4 2.0 L
- 88' Base Beretta
-
Money pit Beretta
- Registered User
- Posts: 6411
- Joined: Thu Jul 26, 2007 11:36 am
- Location: Kansas
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SuzukiGhostRider
- Registered User
- Posts: 2464
- Joined: Tue Feb 12, 2008 4:07 am
- Location: Milan NM
- Contact:
Re: Speedometer help
1st off, you don't have a "v4",lol. It's an I4 (inline 4). 
So, you've put a NEW ,not used VSS in the car, and a KNOWN GOOD cluster, correct? And you STILL have the issue? I can only suggest wire tracing, or checking the ECM out at this point I would say then.
So, you've put a NEW ,not used VSS in the car, and a KNOWN GOOD cluster, correct? And you STILL have the issue? I can only suggest wire tracing, or checking the ECM out at this point I would say then.
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nukkinfuttz
- Registered User
- Posts: 64
- Joined: Fri May 13, 2011 10:51 pm
Re: Speedometer help
The Vss is a Variable Reluctor type sensor. its a coil of wire, and it sets in close proximity to a toothed gear inside of your trans on the differential gear. When the tires are spinning, so is this "reluctor ring". this rotating motion cuases and induced voltage to be applied to the coil in your VSS sensor. The signal is a AC sine wave, it will increase in frequency AND ampliude the faster the wheels spin. it might start out as low as .2vac and increase all the way upto 30vac when going extremely fast (not sure on that, but using those numbers for an example).
This raw signal is sent to the cars ECU where it is decoded and changed into a computer friendly votage called a 5vdc Square Wave. This gets rid of the crazy high voltage and keeps it limited to 5vdc, since the frequency is whats impotant, not amplitude.
Once this signal is recitified, the ECU then divides the raw signal by something like 7.4 SO, lets say your VR sensor is outputting a signal of 1Khz, well, the output from the ECU to the Dash would be 1,000 divided by 7.4 = 135hz @ 5vdc.
The dash knows that 4000 pulses = 1 mile. so, its then looks at the frequency of the ECU output and makes the calculation to determine where to drive the needle.
So, I agree with SGR, if you wanna take a potshot at this thing, replace your ECU with a cheap junk yard swap. that will likely fix you up. However, if that does not, your gonna have to get down and dirty with an osciliscope and a DMM to get to the bottom of this. Give me some feedback on how it goes, and I can walk you thru any further electical tests that need to be done.
This raw signal is sent to the cars ECU where it is decoded and changed into a computer friendly votage called a 5vdc Square Wave. This gets rid of the crazy high voltage and keeps it limited to 5vdc, since the frequency is whats impotant, not amplitude.
Once this signal is recitified, the ECU then divides the raw signal by something like 7.4 SO, lets say your VR sensor is outputting a signal of 1Khz, well, the output from the ECU to the Dash would be 1,000 divided by 7.4 = 135hz @ 5vdc.
The dash knows that 4000 pulses = 1 mile. so, its then looks at the frequency of the ECU output and makes the calculation to determine where to drive the needle.
So, I agree with SGR, if you wanna take a potshot at this thing, replace your ECU with a cheap junk yard swap. that will likely fix you up. However, if that does not, your gonna have to get down and dirty with an osciliscope and a DMM to get to the bottom of this. Give me some feedback on how it goes, and I can walk you thru any further electical tests that need to be done.
Re: Speedometer help
I found a 3.1 L older grand prix at the JY on the weekend, i grabbed the ECM to try the prom chip in my retta thinking maybe its tuned differently, with that Prom chip my spedo goes up to 20 and stays there.... so could be ECM issue...