Contour Enthusiasts Group Archives Forums Modifications Transaxle Tech Question

I am not saying that the PCM does not control the speedo, I am just saying that the FD selection seems irrelevant. the software that is used for the EEC is the same for the 98 and 98.5. Why then is there a different option set? It seems to me that Ford controls what is on the adjustments, not EEC or whatever software you use. They can edit it, but not create new controls... Right? Oh, and Oswald was not alone.

I did lots of thinking on this when I posted it in the sticky at the top of this forum.

The EEC-V system is going to have a common core of programming used on all cars. The extra data that is specific to each car is added on to that common core. I mean it stands to reason that you would not want to program a different engine management computer for every car on the market.....

Now take into account that some cars are rear wheel drive and have the differential in the back. These cars measure the speed at the transmission output shaft, the part where the driveshaft is inserted into the transmission.
If the speedo is driven off of the shaft before the differential then it will be off if you change the final drive ratio. The example would be a mustang with (for example!!) 3.83 rear end and you switch to 4.11 rear end or something like that. The speedo will be off because it is mounted before the diff. In this case you would use the setting in the computer to change the calculation on the computer driven speedo.

With our cars the speedo gear is driven off the differential directly. The differential is always directly linked to the drive axles and wheels and so is technically mounted after the effective gearing. THerefore it is always measuring actual wheel RPM and NOT transmission output shaft rpm.

For further proof I looked at the wiring schematic. On our cars the speed wire goes to a splice, then it branches out into a "Y" with one wire going to the pcm and one wire going to the speedo. If you cut the wire going to the pcm then your speedo would technically still work because there is no wire coming back from the pcm to the speedo.
Our speedos are just electrical speedos driven off of the pulses from the speed sensor, nothing more.

I learned this when I came up with a way to defeat the electronic speed governor of the regular contours while still retaining a functional speedo. I never built the device, but I did come up with a tentative schematic and plan to implement it.

Tom

I've got a '97 Contour with 2.0 L and 5 speed transmission. Back in the summer I replaced the worn out tires with some lower profile 50 series tires and have been driving with the speedometer and odometer reading 8% high ever since. I've always owned Mopars and with those cars, if you change tire size or axle ratio you just correct your speedometer by purchasing a new $5 speedometer pinion drive gear with fewer or more teeth from the dealership. This is the gear under the VSS (vehicle speed sensor). I've been informed by numerous sources that with the Contour you can't change the speedometer pinion gear. Ford doesn't make them. I'm told you have to program the computer somehow but my local dealership won't do it. I too am looking for suggestions on how I can get my speedometer reading accurately again for a reasonable cost. Any ideas?