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The diff mounted speedo also has a circuit module which failed on mine. It is located in the boot (trunk) on the left hand side, very close to the boot light fitting with the wiring and plugs clipped up under the wing (fender) top.
I don't know if the trans mounted ones have a similar unit.
The diff mounted speedo also has a circuit module which failed on mine. It is located in the boot (trunk) on the left hand side, very close to the boot light fitting with the wiring and plugs clipped up under the wing (fender) top.
I don't know if the trans mounted ones have a similar unit.
Steve, great to hear from you. Your observations have been greatly missed, in France, anyway.
Greg
I found the 1984 to 1988.5 wiring buried in the wiring diagram.
These cars do have a speed interface unit item 165 in the attached, I could not find an item location for the speed interface unit. I would be tracing backwards from the speedo and check ALL connections and grounds before replacing anything.
The WY wire from 164 to 153 also goes to the speedo so this is the speed signal.
Mine show a yellow wire from the speedometer transducer ('pulse generator' in my diagrams) going to the speedo, trip computer, cruise control, and service interval counter with no interface....which is consistent with what I've actually found on the cars.
I wonder if what's being called a 'speed interface' is actually the fuel injection interface unit?
What's shown as a 'kickdown inhibit switch' shows in my diagrams as the gearshift mounted switch that allows the cruise control to engage only when the gearshift is in "D". No tie-in to the kick-down circuit.
1984-1988.5 spans the VIN change between trans mounted transducer and the diff mounted pickup. I wonder if this diagram is for the later cars with the diff pickup?
1984-1988.5 spans the VIN change between trans mounted transducer and the diff mounted pickup. I wonder if this diagram is for the later cars with the diff pickup?
Bit of a mystery.
I have two diagrams each of the system using the diff mounted speed sensor and the system using the trans mounted transducer...and none seem agree with what Warrjon posted.
That diagram is from the 1984 to 1988.5 HE supplement from the Original Jaguar ROM
The wiring diagram is labeled
Wiring Diagram B
XJS 5.3 North American Spec upto but not including 1988 1/2 model year vehicles.
The diff mounted speed sensor is in the 1989 model year supplement so probably commenced some time in late 1988, my guess.
In my car the speedo and CC use 8000ppm and the TC uses 4000ppm, It would make sense that Jaguar used the same pulses for the pre diff speed sensor and did not update the CC and TC.
But who knows what Jaguar did, I have come across many inconsistencies in the documentation.
Turns out I have the same diagram in one of my ROMs but never realized it.
The same ROM also has a fold-out diagram labeled 1988½ USA specification that appears to show correctly show the system with the diff mounted speed sensor. I say "appears" because I didn't scrutinize it in detail. Those all-on-one-giant-page diagrams are just too hard for me too read! It's hell getting old
Next warm day of opportunity I'll get the instrument panel re-installed. My guess is the transducer is the speedo culprit. I am going to get a transducer off a local junkyard car rather than spend $100+ for a new one. Spent my budget on the smog pump manifold plugs and bracket assembly. Back to two or more steps forward and no steps backwards hopefully.
12-08-2017, 01:45 PM
