After finishing my 4.9 swap, my speedometer is not working. I have done some searching around and have concluded that because the speedometer is not going to 0MPH but rather stays at about -5 MPH when the key is turned, it is not getting power.

The pertinent info:

4.9l V8 and 4t60e from a 93 Deville swapped into 86 GT 4spd
Ed Parks wiring harness for an AUTOMATIC Fiero. This has caused a couple problems so far since my Fiero was a manual but they have all been conquered.

My question is, once I take the back cover off of the gauge cluster, is there a wire I can splice into to get power to my speedo? Apparently it is not getting power from the C500 or C203, so I figure the easiest way to fix the issue is just to tap into something else up there that is. You wouldn't think the speedometer would require much power, so this should be okay.

Your speedo gets power from the Radio fuse, check that fuse.

My radio works great. Could that be the problem even though that is the case? Going out to check it now.

is it the factory radio, or aftermarket ? Someone could have used a different power source if aftermarket. If not, could be the ground also on the speedo.

I think I'm just going to have one of our local members who is an auto electrician look at it...

Basically what I was asking is this. Is there a wire I can splice into a power source to power the speedo assuming the ground is good? It worked perfect before the swap and I don't think anything was touched in the gauge cluster.

You can tap into any switched power off the fuse box, there are a couple plugs for blade connectors. Some are constant hot, some are switched.

I would check for power with a multimeter on the speedo connector pin T first, and check for continuity to ground on pin P.

Thanks, Mike. I'll go see what I can do.

Thats not the problem. If you didn't rewire the VSS and add the signal converter the speedo won't even zero. The 4t60e VSS can't run the fiero speedo directly. It doesn't send the right signal on its own. The fiero VSS is wired directly into the speedo from teh factory. You need to re-route the VSS wires and add the signal converter between the PCM output and C203. Do you have a scanner? Can you confirm that the VSS signal is getting to the PCM? If its not, you also haven't even felt full power from your 4.9 yet.

I'm pretty sure it is wired correctly, although I hope it isn't if that would mean my engine would put out more power than it does already.

There is a speedo and tach rectifier that was included with the Ed Parks wiring harness. The only thing I can think of that would be causing a problem at this point other than a power issue is the signal isn't getting from the transmission to the ECM. Where is it located on the transmission and what color are the wires going to be going into the plug, if I may ask? My tach did not work because of a very loose plug, so maybe this is a similar issue.

Dont recall what trans you have, if its auto it will be over the right drive shaft output, if manual same place on the trans just not so far to the right. The wires are purple and yellow.

When I bench test speedos when I apply 12vdc and ground they zero, no VSS connected.

VSS is connected...I just found out I have a BIG oil leak on this thing while I was under the car, though, so this is getting put on the back burner for a while. Hopefully it's something easy.

Does anyone know a good method to diagnose where an oil leak is coming from?

EDIT: Oil leak found. My oil filter housing is cracked in 2 places. Trying to locate one locally now...

[This message has been edited by MadDanceSkillz (edited 10-21-2009).]

I am interested to see if you figure out your issue. I have more or less the exact same problem. I will let you know if I get mine working if that happens before yours. Good luck and keep us in the know.

BTW - I found an easy way to test the VSS and the various connections to it is to jack up the back and then with your meter test at each stage while turning the back wheels by hand while the trans is in neutral. You should read a voltage change coming out of the VSS, going into the ECM, and then coming out of the ECM, and going into the speedo itself. Also in my thread someone brought to my attention that its possible that your C203 wires to the speedo could be switched from the factory or a previous owner so make sure you are sending the signal to the right one and not just grounding it out.