In trying to trouble shoot why my electronic speedometer is not working I see that the transducer connected to the transmission sends a signal to both the trip computer (in the dash) and the service interval counter (in the trunk, driver's side). If those items are missing or disconnected will the speedometer still receive a functional pulse signal to make the speedometer work?

1984 XJS (lumped with Chevy 350)

 

The speedometer should receive a signal, it will be the green and yellow wires that are signal. The trip computer and service interval tee off the transducer wires. The speedometer is looking to see 8000 pulses per mile.

I don't have a wiring diagram early enough, but do you actually have the transducer, or a the differential mounted sensor? My memory is that around that time was the changeover, but I could be off on the date

 

Yes, assuming the wiring wasn't actually damaged

Cheers
DD

 

The diff mounted speed sensor was introduced mid-1987 calendar year

Cheers
DD

 

As mentioned and adding my findings over the years.

RHD, so you can apply what is what for LHD.

The Green is the Ign signal TO the transducer.

The Yellow is the signal TO the units in the car that use the pulse.

Look VERY CAREFULLY at the loom about 10" from the transducer. I have had 3 of these looms jammed between the trans mount bracket and the body, OOPS.

Inside the beast.
LH side on the console, remove the cheek, pull the carpet as required, and FIND THAT Yellow WIRE. It splices in that area for:
Speedo
Cruise Pulse
Trip Computer.
We NO GOT service counter nonsense. That info is in our brains, haha.

Check the Green wire for Ign ON signal.

Transducers fill with oil. Some respond well to a flush out with Solvent (Carby cleaner P/Pack), some do not. There are different tranducers, mainly the nut/knurled ring, at the trans.

The nylon Drive gear inside the trans, goes AWOL due to age. Its a GM item, so take it to the GM mob, and ask for one the same colour. The colours are for different diff ratios.

Thats about it, simple really.

 

OK, thank you very much for the great response. Looks like I have what I need to investigate further. I just wanted to make sure that if one of the other components receiving a signal from the yellow transducer output wire were bad, missing or disconnected that the speedometer would still receive the signal (assuming the wires and connectors were all good).

From what I'm hearing you all say it sounds like the speedometer should still receive the pulse signal regardless of the other components. That's good since I'm not sure if those other components are still functioning since the previous owner cut and removed a number of wires under the hood when the V8 conversion was done.