Loss of speedometer/ odometer - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 09-02-2016
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Location: galena mo
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Loss of speedometer/ odometer

Hello, Im Tom. First I would like to say I have used the search engine extensively. I have always been good at using keywords however I cannot find anything useful even on google. I have a 99 Mazda B4000. My first question is where can I find an accurate diagram of the power distribution box under the hood? I have found diagrams of the box inside the cab which are accurate as far as I can tell. One thing I do not understand is that im seeing owners of the same truck saying the box is under the passenger side kick panel. Mine is on the side of the dash on the drivers side.

Recently I took the GT Grant wheel out of my 72 Chevy and put it in my Mazda. I was able to do this without buying any parts. I pulled the cast aluminum piece with the three bolt holes off my C20 and put it directly on the Mazda. Obviously I unhoooked the air bag and cruise control, i also unhooked the piece that sets off the chimes when you leave the key in. My truck was fine for a couple days aside from throwing a few codes for the air bag.

The real problem started when I mounted a switch with two terminals to my dash and used it for my overdrive switch. The switch worked about three times before it quit and I unhooked it and I believe the speedometer and odometer were not functioning as soon as I started the truck. I do not know if I shouldve used a switch with three terminals and ran a ground or what. I know just enough about electrical to really screw things up as ive done here.
I have checked all the fuses and there were a couple blown but they were replaced. I know there is a speed sensor on top of the differential, I was hoping to find the source of the problem and make sure that was it before I spent 60 on a new one.

I was hoping there was a relay under the hood to delete the air bag and cruise control all together, but I could not find a diagram. It is too big of a coincidence to ignore that my speedo quit as soon as I mounted this switch, so im hoping somebody can figure out what happened here, whether I somehow fried the speed sensor or if theres still a short somewhere that hasnt been addressed. I remember doing the exact same thing in my chevy when i tried to hook a similar switch to my amp, it worked for a second and then my amp went off and only came back on after i took it apart and cleaned it which mysteriously worked. Needless to say I am done trying to put switches on things.
Thanks, -Tom
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Old 09-02-2016
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Well 1999 B-series would have the cab fuse box on drivers side, in the early 2000's they moved it to passenger side and it was renamed the Smart Junction Box(SJB), they called it this because Ford/Mazda got rid of the GEM(generic electronic module) at that time and combined its function with fuse box, so "Smart" Junction/fuse Box.

Not sure what you are doing with the switches???

The control systems in vehicles made after 1995 use the computer to run pretty much every thing, or a GEM for some things.

For the transmission over drive any switch would be telling the computer to either use OD or not use OD, it won't be connected to the transmission directly.
So a Factory OD switch, would most likely just be a Ground for 1 pin on the computer connector, i.e. if wire/pin is grounded then no OD, if no ground then used OD

They very rarely use 12volts for any controls any more, they send 12volts to everything when key is on but leave it unGrounded so it is OFF, to turn something on they Ground it.
This saves lots of money and is safer than running 12volt wires every where.
And since body and chassis are Grounds you only need 1 control wire for any switch, it is just grounded to cab.

VSS(vehicle speed sensor) can run 2 different ways in your year.
If you have 4 wheel ABS then VSS wire runs to 4WABS module where signal is converted for tire size and rear axle ratio, and then sent out to Speedo/odo, Cruise and computer.

If you have Rear wheel ABS the VSS signal goes to GEM where it is converted for tire size and axle ratio then sent out to Speedo/odo, Cruise and computer.
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Old 09-02-2016
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Quote:
Originally Posted by RonD View Post
Well 1999 B-series would have the cab fuse box on drivers side, in the early 2000's they moved it to passenger side and it was renamed the Smart Junction Box(SJB), they called it this because Ford/Mazda got rid of the GEM(generic electronic module) at that time and combined its function with fuse box, so "Smart" Junction/fuse Box.

Not sure what you are doing with the switches???

The control systems in vehicles made after 1995 use the computer to run pretty much every thing, or a GEM for some things.

For the transmission over drive any switch would be telling the computer to either use OD or not use OD, it won't be connected to the transmission directly.
So a Factory OD switch, would most likely just be a Ground for 1 pin on the computer connector, i.e. if wire/pin is grounded then no OD, if no ground then used OD

They very rarely use 12volts for any controls any more, they send 12volts to everything when key is on but leave it unGrounded so it is OFF, to turn something on they Ground it.
This saves lots of money and is safer than running 12volt wires every where.
And since body and chassis are Grounds you only need 1 control wire for any switch, it is just grounded to cab.

VSS(vehicle speed sensor) can run 2 different ways in your year.
If you have 4 wheel ABS then VSS wire runs to 4WABS module where signal is converted for tire size and rear axle ratio, and then sent out to Speedo/odo, Cruise and computer.

If you have Rear wheel ABS the VSS signal goes to GEM where it is converted for tire size and axle ratio then sent out to Speedo/odo, Cruise and computer.
Thank you for your input. I think I understand what you are saying. I forgot to clarify, the wires on my stock overdrive switch broke off deep inside the switch. Too deep to splice.I have a custom shift lever I was wanting to use and was hoping I could keep the option of turning od off with a switch on the dash.
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