View Full Version : Broken Speedometer..?

02-15-2007, 07:26 PM
My speedometer started acting funny, (jumpy needle) and now it's dead. The needle now doesn't move at all and it isn't clocking miles. All the other guages work.

Someone told me I should check the little gear on the speed sensor, that it's plastic and sometimes the teeth could get chewed up, but it's fine. I even replaced the speed sensor since it was only $29 from FORD, but that didn't do anything....?

I really wanna fix this thing b/c since the speedometer stopped working she stalls when I come to a stop / brake. I would think the two HAVE TO be related cause it started at EXACTLY the same time, but certianly I'm no mechanic.

Any help would GREATLY be appreciated. THANKS.

02-15-2007, 08:41 PM
Oooops It's a 98 Cobra

02-15-2007, 09:06 PM
It sounds like your speedo cable has gone south. I would take the transmission side off and see if that is the problem.

02-16-2007, 04:55 PM
Speedo cable..? I was told it was electronic..?

02-16-2007, 08:34 PM
1999 and up are electronic...

02-17-2007, 05:39 PM
There is no speedometer cable running to the transmission though...??? Just two wires that plug into the speedo sensor.

And the parts guy at FORD seems to think it's electronic also, I made him well aware it's a 98'...?

02-18-2007, 12:57 AM
Now you got me thinking...I knew 99 and up was electronic and I was pretty sure it was the first year???? :doubt:

02-18-2007, 11:20 AM

I believe that you are correct. Whe I was doing research on the correct speedo gear for the 3.73 gears in my '94, I came across several different documents that said '99 was the first year for electronic speedos. I know that one of those documents was direct from Ford.


02-18-2007, 11:31 AM
The speedo itself may be electronic in the 99+ . However, consider this, if the speedo has a digital odometer on it, it has a 90% chance it is completely electronic eventhough it is analog. The 99+ model year was when they included the diagonsitcs function on the digital odometer as an added hidden bonus. Chances are there may be problems with the connections at the speed sensor, an issue with the PCM (powertrain control module, or the speedo itself. It may be possible to remove the speedo and push it back into place to reseat the connection pins. Probably more trouble for what it is worth even if you replace it you may still have problems.

If the check engine light has not come on, or if you tried to pull any codes from the ODBII port and nothing appears, more than likely the PCM (or ECU) is receiving data from the speed sensor. If this is the case, it could be related to a faulty GEM control unit which usually processes the data for display on the instrument cluster. The GEM control units (there may be several of them) also have memory similar to that of the PCM but you cannot access the data from the ODBII port. In some cases, faults or issues when associated with the GEM units can be corrected by disconnecting the battery or by pulling all of the GEM associated fuses for 5 or 10 minutes. Trying to diagnose a GEM issue can take a considerable amount of time especially if it is just a simple issue with one of the circuit boards that may have an open solder joint. I had an issue with my 96 Exploder where one of the headlights would not work. With several hours of searching on the net (after attempting to determin why there was no voltage at the wiring harnes for the lights) turns out that one of the GEM units was susceptable to open circuits due to poor soldering.

I found this when doing a search on 89 mustang speedometer failure:
sorry it starts from 99. but I will look further.

Ford ODBII codes, look at p0500, p0501, p1039 which is related to the speed sensor

There are some sources for programming or calibrating the speedometer which includes the 98 mustang, that would make me assume it is electronic.
http://www.speedoshop.com/pages/index.php?page=jprog3 This probably will not help you.

There may be an existing TSB or recall on the speedo for the 98 since I have seen too many listings for other Ford vehicle of the same model year under recall or listed as having speedometer failures.

02-18-2007, 08:29 PM
Check for blown fuse. I believe the speedo is on the same circuit as the cigarette lighter. I blew mine once and the speedo quit.