speedometer not working right

Reply Subscribe

Thread Tools

Search this Thread

Jan 6, 2013 | 03:40 PM

mattg529

Thread Starter

New User

Joined: Jan 2013

Posts: 7

Likes: 0

From: Madison, WV

speedometer not working right

I just recently bought a 1997 ford f150 xlt. The man I bought it off of said he changed the ECM and the speedometer stopped working. Here is the troubleshooting I have done so far. I checked the ECM and the ECM part number matches the one on the passenger door. When I hook up the VSS on the rear nose cone on the transfercase the speedometer will work but, I am traveling approx. 35 mph the speedometer says 95 mph, and the odometer doesn't move at all. On the transfer case I have 3 connectors 1 is a 4 wire connector, 1 is a 1 wire connector, and the VSS is a 2 wire connector. Do I have a bad VSS or is it something else?
specs.
1997 Ford f-150
4.6 liter engine
Manual Transmission
4wd
Any help would be appreciated thanks.

Jan 6, 2013 | 04:51 PM

vaper

More Turbo

Joined: Aug 2011

Posts: 544

Likes: 2

Almost like the ecm thinks it's in low range.I had 92 f250 7.3 e40d do that because of a blown fuse but it was the shift patterns that were all screwed up.
Speedo was right but it would go into 3rd gear at about 15 mph

Jan 7, 2013 | 09:34 AM

F100classics

Freshman User

Joined: Mar 2008

Posts: 28

Likes: 1

From: spokane wahington

The gear on the VSS itself or the gear in the tail housing, on the output shaft, need to be perfect for the speedometer to work correctly. If they are worn at all the speedo will jump or miss calculate your speed. the gears are made of plastic and my 1997 flareside's speedometer was off and would "jump" on the freeway. It's something to look into.

Jan 7, 2013 | 01:15 PM

mattg529

Thread Starter

New User

Joined: Jan 2013

Posts: 7

Likes: 0

From: Madison, WV

ok thanks I will check the gear on the VSS and the transfercase.

Jan 11, 2013 | 01:39 PM

mattg529

Thread Starter

New User

Joined: Jan 2013

Posts: 7

Likes: 0

From: Madison, WV

Finally got all the parts today. and changed the ABS speed sensor on the rearend, and changed the speed sensor on the transfercase. I still have the same speedometer problem. I also checked the ECM again just to make sure it was right, and checked the plug to the ecm and it was all good. Just don't know where to go now. Someone said that there is another speed sensor on the transmission, but I can't find another one. Is there really another speed sensor? Thanks

went back out to troubleshoot a little more and decided to check voltages on the speed sensors. I have 5.00 volts on the sensor on the rear end, and 0.00 volts on the sensor on the transfer case. I was under the impression that there should be 5 volts on both of them.

Jan 11, 2013 | 02:39 PM

vaper

More Turbo

Joined: Aug 2011

Posts: 544

Likes: 2

speed sensor issues - Ford Truck Club Forum
Apparently the vss on the tansfercase is only for the shift module,the one in the diff is for the speedo.Maybe a wire broken somewhere?

Jan 15, 2013 | 04:54 PM

mattg529

Thread Starter

New User

Joined: Jan 2013

Posts: 7

Likes: 0

From: Madison, WV

Did any 97 f150's come with 4 wheel ABS? I can't find any sensors on the front of my truck, and when I used the VIN decoder it said it has "class D" brakes. My question is can the ABS control module be at fault because it is the only thing I haven't checked? Also where is the module located on the truck?