View Full Version : Speedo not Working (Still)

01-23-2008, 09:44 PM
Well, after tearing into the dash and finding the speedo gear totally intact (except now it isn't because it took destuctive forces to remove it) I am back to square one in finding out why the speedometer and odometer do not work.

Without them working, it creates an engine code and then I cannot get the car inspected (why do I need to get it inspected you ask? Because by late February I have to bring proof of inspection before the judge!).

The code is P0500 Vehicle Speed Sensor Malfunction which includes various symptoms:

loss of anti-lock brakes
the "anti-lock" or "brake" warning lamps on the dash may be lit - Yep, I removed the lamp to see what will happen next
the speedometer or odometer may not work properly (or at all) - Yep
your vehicle's RPM limiter may be decreased
the shifting of an automatic transmission may become erratic
other symptoms may also be present
One day while driving the speedo started acting up...it would work, then it wouldn't, then it would. Now it doesn't at all...that includes the cruise control.

A code P0500 may mean that one or more of the following has happened:

The Vehicle Speed Sensor (VSS) is not reading (functioning) properly
There is a broken/frayed wire leading to the vehicle speed sensor
I replaced the VSS with a new one and that did not fix anything (so there's something else I bought that I didn't need to).

I am at a loss as to what I should do next.

BTW, here's my little corner of the garage where I break things then fix them:

01-24-2008, 04:14 PM
I'm not sure what the problem is but I know when I had my old Honda Civic you could unplug a wire under the hood and it would stop the speedo and the miles from working. I don't now if Ford has something like that or not but it is worth looking into....

BTW...It looks like someone is drinking on the job... :drunk: :nono:

P.S. you might want to have that MOLD looked at.. :bugeyes:

01-24-2008, 09:19 PM
Have you checked the cable going into the tranny? The plug could have come unplugged or the internal speedo gear broke? Just throwing ideas out there.

01-25-2008, 01:25 AM
Have you checked the cable going into the tranny? The plug could have come unplugged or the internal speedo gear broke? Just throwing ideas out there.

CobraPace94 makes a good point: You might try using an Digital Volt Meter (lowest resistance ohmmeter setting selected) in league with jumper leads of various lengths to check continuity from point-to-point in the speed-o wiring harness, from tranny to wherever. (The color-coding of individual wires should help you locate each of the two points in the respective sections of the harness.) You might also try spraying contact cleaner onto the various connectors involved and see if unplugging then plugging them back in after contact-cleaning has any effect. Oxidized contacts on connectors can sometimes be a pain on the rump, especially if you live near the ocean or in a place where they put salt onto the roads in winter.

While you're at it, a visual inspection for crimped, crushed, or shorted wires might yield the guilty party. (You might still be able to measure point-to-point continuity while there is also a short to ground that de-activates the circuit.) The Haynes Manual for the car ought to offer sufficient wiring diagrams to give you a good idea of what connector and what individual wire feed what circuit. (The Haynes Manual might also offer tips, shortcuts, or "tricks" for diagnosing the faulty circuit.)

best wishes in finding the problem,
--Professor Chaos

02-11-2008, 08:20 AM
I am still hunting this gremlin down...I have checked the gear inside the tranny, although that's pretty tough since you're looking down a tunnel...it looks like a worm gear and I don't see anything wrong with it.

I also checked the voltage drop across the connectors in the plug and am getting roughly 1 volt, which I believe is normal.

BTW, there is another plug into the tranny housing on the same side...more toward the front. What is that? It's connectors are not in great shape.

HELP!! This is driving me crazy!

And Phil...I was drinking and the mold is from an old refigerator that used to be there. I am painting that wall (Killz first) and hanging some cabinets...

02-11-2008, 12:24 PM
Not trying to insult anyone, but did you check the fuse. I blew that fuse once on my '01 Cobra. It was on the same line at the cigarette lighter. My problem was from a short in the circuit caused after I had removed the shifter bezel.

Just trying to help. :D

02-22-2008, 12:45 AM
If you replaced the speed sensor already and that is still the error code indicated, I would begin to suspect connector issues, or it might be that the speed sensor was indeed bad, and it took the fuse with it when it failed. (Since there is electro-mechanical deflection in the speedometer circuit, there is probably a fail-safe built into the circuit, to prevent the speedometer from beating its own brains out in the event of a short or excessive current.

If the fuse is fine, I would then begin to perform a point-to-point continuity check in the wiring harness (with the car's battery disconnected--obviously--), to make sure there is not an open wire or connector. Connector contacts fail regularly, so connector failure is a much more likely occurrence than is wire failure, but sometimes wires get pinched or cut during maintenance.

best wishes in nailing the problem
--Professor Chaos

02-26-2008, 02:55 PM
In thinking back, the problem first ocurred a week or 2 after I cleaned the throttle body...what is from the TB to the firewall that may have been kinked/broken/dislodged that would be electrical? And I think its electrical because from time to time, the speedo will work for a few seconds...