replaced VSS, speedo still won't work (update)

[nda0602v6]

I'm trying to get the speedometer to work on a 94 Camaro. I replaced the vss sensor tonight (the sensor mounted on the end of the tranny) but the speedo still doesn't work. I did a search on here in regard to speedometers but couldn't find any usefull info. According to my haynes manual, the wire diagrams show the speedometer gets its signal from a Green W/ white Stripe wire which is the VSS output wire. Okay, if I find this wire behind the dash, how can I test it and what specificly do I need to test for...volts, ohms???

94-Camaro w/ 3.4L, auto. I even checked every fuse in the car (side of the dash and under the hood), all are good. Thanks for any info.

[ August 16, 2005, 09:24 PM: Message edited by: nda0602v6 ]

[Need4Camaro]

Chances are your car knows how fast you're going then because if the VSS was out, your car would be locked in 1st gear... So it's an error between the Speedometer and PCM...

Mine is like that too only it goes off and on... very annoying trust me... Unfortunately I havn't found the problem yet...

[HBHRacing]

The VSS simply makes an AC volatge signal. Use a multi meter that has this scale to test it and see that it is indeed making it. If it is the problem is between the PCM and the cluster.

[nda0602v6]

Originally posted by HBHRacing:
If it is the problem is between the PCM and the cluster.

I have a multimeter so I'll check to see if the voltage changes. Can I perform the same test between the PCM and the cluster?

[Need4Camaro]

Originally posted by nda0602v6:
</font><blockquote>quote:</font><hr />Originally posted by HBHRacing:
If it is the problem is between the PCM and the cluster.

I have a multimeter so I'll check to see if the voltage changes. Can I perform the same test between the PCM and the cluster? </font>[/QUOTE]I would imagine but here's where I was stomped... I couldn't find the wires period yet my Speedometer works occasionally so they DO exist...

[fenderman]

If this Camaro has cruise control you may want to try and activate it. The reason I am suggesting this is because the cruise control is fed from the same VSS wire that the speedometer is. If the cruise control functions you know that the problem lies in the cluster. If the cruise control doesn't work then you can go back to suspecting the wiring.

If I were to suspect anything at this moment I would suspect the speedometer itself or a break in the wiring. Let us know what you find out.

[Need4Camaro]

Originally posted by fenderman:
If this Camaro has cruise control you may want to try and activate it. The reason I am suggesting this is because the cruise control is fed from the same VSS wire that the speedometer is. If the cruise control functions you know that the problem lies in the cluster. If the cruise control doesn't work then you can go back to suspecting the wiring.

If I were to suspect anything at this moment I would suspect the speedometer itself or a break in the wiring. Let us know what you find out.

Hey thanks... My Cruise control doesn't work when the speedometer goes nimzit... However activates just fine when the speedometer returns steady... I have also replaced my VSS to no avail... Where should I check now?

[fenderman]

I'd say the next thing to have done is to have a check run on the PCM to see what signals it is getting and what signals it is giving. To me it seems like a bad connection either caused by a short or corrosion.

First though I would check the PCM connector to make sure it is tight and you may even want to disconnect the battery and pull the PCM connector off to see that none of the wires are loose and that the connections aren't corroded anywhere. Trace the wiring harness if possible in the engine compartment and make sure there are no spots where the harness has rubbed through creating a short. If you can locate either the speedometer's or the cruise control module's green w/ white stripe wire run a continuity check to make sure that there is no break within the wire itself between the PCM connector and the component. If all these things check out I would have the PCM checked.

The instrument cluster shares a common ground so you can safely rule out a bad ground as your trouble if all the other gauges work. The components are laid out very simply. The VSS has a yellow wire and a purple wire both leading to the PCM. From there the VSS signal is processed and translated to the green w/ white stripe wire which leads to the cruise control module and the speedometer.

Since both the cruise control module and the speedometer seem to go on the fritz at the same time I would rule out those two things because one is not dependent on the other- the wire simply branches off so one failed component would allow the other one to work. For some reason there is no signal travelling down the green w/ white stripe wire. You say that you've replaced the VSS so it would be safe to eliminate that as well. That leaves a green w/ white stripe wire, the PCM, and a yellow and purple wire to be checked because that is all that is left in the circuit. Good luck!

[nda0602v6]

Alot of good info.....thanks. After work today I'm going to start testing things with the multimeter. I'll post an update on what I find out.

[nda0602v6]

Originally posted by Need4Camaro:
Chances are your car knows how fast you're going then because if the VSS was out, your car would be locked in 1st gear...

I did a series of tests tonight and what you mentioned is not correct. I completely unplugged the plug that plugs into the VSS, started the car and put it drive....no locking of any kind. (had the rear of the car on jack stands to let the rear tires spin while in gear).

Next test I did was a test as mentioned in Haynes repair manual on how to check the VSS. With the VSS unplugged, I performed a "refference" check by probing the yellow (+) and Purple (-) wires right at the plug with my volt meter. According to Haynes, I should have seen roughly around 5-volts; I measured 0 (zero), the meter never budged. (tried testing with car on and off, still nothing). Thinking there may be a break in the yellow and purple wires by the time they reach the pcm, I pulled out the pcm and probed the wires directly at the pcm's main plug.....still 0 (zero) volts, not a damn thing. From what I can tell, there are two Green w/White striped wires that come out of the pcm, they are side by side. I was able to follow the one and it lead to the cruise control module. (this wire routes through the flex loom tubing in the very front of the car). I followed the other Green w/White striped wire and it head back by the firewall and from what I can tell...it runs through the firewall into the car.

With the VSS plugged back in, I even tested both Green W/White striped wires coming out of the pcm...absoutely nothing. (tried testing with AC, DC, OHMS) Only thing I can think of is the pcm needs replaced?

[HBHRacing]

Chrysler trannys will default to 1st gear without the VSS input. GM's will not. They use RPM, TPS and MAF to establish shift points.

[nda0602v6]

Originally posted by fenderman:
If this Camaro has cruise control you may want to try and activate it.

forgot to mention....yes I tried that today before I started testing any of the wiring, The cruise don't work. I followed the green w/white stipe wire from the cruise control unit (located on the drivers side) and found that it travels in a thick wire harness that works its way around the very front of the car and comes out close to where the battery is. I followed the wire directly to one of the main connectors on the pcm, didn't find any other green w/white striped wires that T'd off from it along the way. Since there were two green w/white striped wires right next to each other on the pcm's plug, I'm wondering if that wire goes to the cluster. I'd like to get my hands on a shop manual the dealers use since they not only go by wire colors, they tell you what PIN number each wire goes to on the plugs. I do believe the green w/white striped wire was at PIN 7.