1990 (mechanical speed sensor) cruise control problem (1 Viewer)

[Tyx]

Hey all =) Long time lurker, first time poster.
Been doing a heap of work to one of my 80s of late and fixed near everything, but cruise control continues to elude me. It's never worked in either of my 1990 80 series =(

Thanks to the plethora of threads on the topic here I've completed the tests using the cruise control stalk and start to fail at the over 25mph test where the cruise dash light simply stays on rather than starting to flash.

Sounds like an easy speed sensor fix from what others have had, but I'm blessed or perhaps cursed to have an entirely mechanical speed sensor / speedo. Meaning there are no electrical wires coming from it to have been compromised. Was tempted to just order a new speed sensor anyway but it seems impossible to order one that isn't producing electronic output.

I've also unplugged the brake fluid sensor unit (though it's full as can be) to no avail.

I only have the Gregory manual for this car and have already gone far beyond it's scope of troubleshooting - having no luck finding anything about cruise in the various FSMs that seem to exist for this car either.

The only components left to look at are the ECU itself (which I assume is at least mostly functional given it can generate my cruise test codes correctly) and the actuator.

I'd really be flying blind with either owing to the lack of info I can pull up on them. These symptoms sounding familiar to someone with the same mechanical speedo setup? Are ECU / Actuator likely to be fixable or am I bracing myself for trying to hunt down new parts to buy??

Many thanks.

ps. HDJ80 auto if that's of any relevance.

 

[Tyx]

Actuator tested and seems OK, though feels like pretty piss weak motor... as in possibly not enough to actually actuate sufficiently to pull the throttle cable.

Assuming that's OK though it pretty much leaves the speed sensor. How does the Actuator even talk to the speed sensor when the sensor isn't electronic in any way shape or form? Either the combo cluster is taking some kind of translation of speed from the gauge and sending it through, or I'm actually driving a car with a critical missing component for the cruise and just made to look like it has it? XD

in which case, can I just get a new combo cluster and speed sensor which is electronically inclined and swap them in? Can't think of any differences that would exist between the cable and electrically driven speedo except my odo will be reset

 

[Tyx]

Speed Sensor unit (with +20% correction for 35" tires). No wired to feed a reading to CC ECU

 

[Mixelplix]

I'm not sure how much help I'm going to be considering mine is a 91.

Did the 1990 come originally all mechanical? I would assume the ECU would need some sort of electrical input.

My 91 is running the exact same setup as you, including the adapter to modify the speedometer - however, I have a speed sensor on the transfer case side of the adapter with a wire that runs up and over the transfer case to the right side of the vehicle. Could it be as simple as you're missing the speed sensor?

 

[Mixelplix]

This is what my VSS looks like (picture from a google search)

 

[Tyx]

Cheers Mixel. My other 1990 80 series also looks like your pic (minus the ratio adjustment as it's still on stock size).

Given the one I'm trying hardest to fix up has an actuator, steering wheel controls (stalk) and presumably an ECU I have to imagine that one of 2 things is the case:

1. It did used to have a setup like your picture and has since been pulled including the wires that run off over the transfer case
2. It's all still as original and there's something in the meter cluster that takes an input from the speedo itself and sends an electrical signal to ECU (have seen a few posts across the many CC threads I've looked up that indicate such may be possible but no one's really certain)

I'll be visiting local Toyota dealer today and while my expectations are very low for any useful help on such an old car I'll see if they can't point me in the right direction. Preference is to use the existing components to make my cruise function but if I need a whole aftermarket thing than so be it. Too many highway km between tracks in my travels

 

[Tyx]

Noticed my Odo was stuck so pulled that apart to have a clean. I don't have diagrams to work with that specifically detail the what's and where's on the instrument cluster - but it certainly looks like there's some signal being taken from the speedo/odo cluster and going back to the loom via the switch that the speedo needle rests on when at 0... whether that carries a signal for the CC ECU or not I may never know XD

Out of interest anyone know what pressing that guy does? that will probably tell me what those wires are about

 

[Tyx]

That's the timing belt reset switch I guess... so probably I just have the wrong speed sensor and need to get a new one + run the wire up to ECU if I can find it