No Speedometer/Odometer - Intermittent (1 Viewer)

[thedoughboy]

1995 - 300,000+ miles

As the title says, my speedometer/odometer is not working intermittently. The pattern is, initially both work, after about 5 miles of driving both stop working. I have read through all of the posts I could find. Most fix this problem by replacing the VSS. My VSS is good. I believe it is a damaged wire or connection point between the transfer case and the gauge/ecu. This is what I know:

• VSS checks out
• I have pulled my gauges and everything looks brand new. That is, no apparent heat damage to the circuits behind the speedometer.
• I have an Ultraguage. It too is reporting no speedometer/odometer.
• When not working, the speed control does not work.
• I have cleaned and reconnected the plug on top of the transfer case.

So, does anyone have experience with likely locations for the wires to fail? Can anyone provide the wiring schematic for the VSS to the gauges and ECU?

As always, your help is GREATLY appreciated!

 

[jonheld]

There's nothing on the top of the transfer case related to vehicle speed, so I don't know what connector you're referring to.
The speed sensor is on the left side of the rear extension housing of the transfer case. It has a 3 wire black plastic connector that is removable.

The Toyota factory service manual (FSM) and electronic wiring diagram (EWD) are available to download in the resources section.

 

[thedoughboy]

@jonheld The connector I am referring to is boxed in red. The red line shows the wire wrap that goes to the 3 wire black plastic connector you reference.

 

[jonheld]

As shown in the EWD for the combination meter, the speed sensor passes through 3 connectors on its way to the speedo. If you are certain that the VSS is 100% good, then proceed with testing the wiring.
I would make certain that the VSS is getting a good +12 on pin 1 and a good ground on pin 2. Without those 2 you'll get a whole lot of nothing.
Pin 3 is the actual tack pulse out to the speedometer. An oscilloscope would come in handy to check that.

 

[thedoughboy]

As shown in the EWD for the combination meter, the speed sensor passes through 3 connectors on its way to the speedo. If you are certain that the VSS is 100% good, then proceed with testing the wiring.
I would make certain that the VSS is getting a good +12 on pin 1 and a good ground on pin 2. Without those 2 you'll get a whole lot of nothing.
Pin 3 is the actual tack pulse out to the speedometer. An oscilloscope would come in handy to check that.

Thanks for the advice. I will check the +12v and ground wires.

 

[Mjones]

As shown in the EWD for the combination meter, the speed sensor passes through 3 connectors on its way to the speedo. If you are certain that the VSS is 100% good, then proceed with testing the wiring.
I would make certain that the VSS is getting a good +12 on pin 1 and a good ground on pin 2. Without those 2 you'll get a whole lot of nothing.
Pin 3 is the actual tack pulse out to the speedometer. An oscilloscope would come in handy to check that.

Interesting thread.

I don't want to get too off topic but curious if this is related to a bad tach reading I'm getting on my '96. It's only the tach for me that goes out and not always - there doesn't seem to be a pattern to when it goes out - my speedometer hasn't gone out beofre. I've got a tach that intermittently stays at zero after starting the car and remains at zero until turn the car off and restarting it. Other times it functions properly when starting. When bad, it sits at zero rpm but then will jump to exactly a 1000 rpm over the correct rpm in acceleration when the transmission downshifts and then back zero when the transmission shift back and/or throttle let off. I know the correct rpm but Ultraguage shows the rpm correctly. So I know the rpm is getting info out that Ultraguage can pick up.

Related to this? Thoughts?

 

[pedwards]

Do they both drop out at the same time? If so, maybe there is a faulty common ground, maybe in the instrument cluster ?

 

[Mjones]

Do they both drop out at the same time? If so, maybe there is a faulty common ground, maybe in the instrument cluster ?

Just the tach drops out at zero seemingly randomly. My speedometer hasn't dropped out.
I could see it being in the instrument cluster. I need to pull it and see if loose pin or what.

 

[jonheld]

Just the tach drops out at zero seemingly randomly. My speedometer hasn't dropped out.
I could see it being in the instrument cluster. I need to pull it and see if loose pin or what.

The tachometer is fed from the ECU in your truck, so other than being in the dash cluster and getting fed with tach pulses, not really related to the speedometer.
Again, all the documentation is available to download free-fer-nothin in the resources section.