Cruise Control Computer

[Piratetip]

Alright, I didn't want to but here we go.
I have been diagnosing my cruise for a couple hours now and narrowed it down to the computer.(maybe)
Cygnus, and my 3 separate manuals don't show the location, so I need some input.

Where is the Cruise Control Computer Located in a 1987 GTE MT?
Pictures would help.
Thx.

Nick

 

[isnms]

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=15

 

[Piratetip]

LOL, thx dude. That dosn't help me.
The year is incorrect for the Cygnus manual reguarding cruise control.
I need 87'

 

[jetjock]

It's in the book. Look harder . It's the same place on 87s (under the dash on the left side).

Btw, Toyota puts out a separate manual on the system. Not that you need more than whats in the TSRM to repair it but this manual explains in detail how it works. I happen to have one if you need to know something.

 

[Piratetip]

You know off hand what color it is? That would help.

 

[isnms]

It's in the same general location:
http://www.supra.co.nz/87tsrm/New_Car_Features/ncf13.htm

 

[Piratetip]

For future reference the Cruise Control Computer is bright green.
Jammed back behind the super monitor control where you can't read it.
Is labeled Speed Control on the box.

Can anyone confirm this?

 

[jetjock]

Yeah, that's it. What the problem you're having? Did you run the diagnostics? If so codes?

 

[Piratetip]

My cruise decided to stop working one day. I was intermittent for awhile then turned off all together.
Tried to run the diagnostics, but nothing came of it.
The cruise does not work at all, when I hit the button there is no green light anymore.

Haven't really found the problem yet.
Ok what I have done thus far.
1. Checked correct working order of parking brake.
2. " " of brake light switch.
3. Checked clutch switch, something was funny with it, have to recheck.
4. Vacuum lines are all good.
5. Checked correct working order of vacuum pump.
6. " " of Actuator.
7. " " of Vacuum switch.
8. ECU-IG fuse is good.
9. Took apart the clock spring in the steering wheel. Everything was perfect.
10. I get voltage through the relay in the switch through the steering column.
11. Brake fluid switch is good.
12. GAUGE fuse is good.

Checks on CCC or Speed Control unit I should say.
Located here. http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=BE&P=80
Everything checks out except the clutch switch is strangely high resistance when pushed in. 2.4 Mega ohms. No continuity when released.

Any ideas now?

Edit: I also took apart the cruise switch to make sure everything was working a ok. It checked out ok, I can feel the relay click when I hit the button.

 

[Piratetip]

Nothing appears to be burnt, broken or leaking inside the Cruise Control Computer/Speed Control

Edit: If someone wanted to see an 87' Unit here are pictures.

 

[jetjock]

No green light tells me the switch is bad or not receiving power. Not to mention without it you can't do the diags. You have voltage on pin 10 of the computer when the switch is turned on right? Got a good ground on pin 13?

 

[Piratetip]

The switch is bad even though the relay inside is working correctly and has power through it to the resume accel canc buttons?
Yup batt voltage on pin 10.
Good body ground on pin 13.

 

[jetjock]

The main swtch doesn't directly supply power to resume, accel, ect. If the switch is good (and it sounds like it is if you're getting power to pin 10) then the computer isn't turning the led on. It should do that no matter what the other inputs are doing. Sounds like a bad computer alright.

 

[Piratetip]

Bad computer conclusion.
Have an extra?

 

[jetjock]

Nope, sorry. Of all the spares I have that's one I don't. I'm sure someone else does though. Truthfully, yours would be the first case I've seen of a bad one. Based on the tests it sure sounds like it though. Good job on that btw...

 

[Piratetip]

Alright thanks.
I'm still curious about the switch though.
The speed control does more than just cruise though doesn't it? I would think something else would not be working correctly if this part died.

 

[jetjock]

Nope, that's all it does. It receievs input from many things true, but all it does is control the CC actuator.

You could check the switch by itself but since the relay inside is passing power to the CC computer it must be good. The LED could be burned out but I doubt it. Bring 12 volts to pin 6 on the switch and ground pin 4. The LED should light up. If it does and you're sure the computer has power and ground it's likely dead. If the LED turns out to be dead you could hook everything back up and check to see if pin 3 on the computer switches to ground when the main CC switch is turned on. That's the signal to illuminate the LED. If it does, enter diagnostics and count the pulses on your meter, but I'm pretty sure you'll find the LED is good.

Otherwise you did everything right. You studied the system, checked for power without forgetting ground at the device (something that bites a lot of people) and decided the box must be bad. You then checked everything to ensure a new box would likely fix things and nothing else in the circuit would pop the new one, or was responsible for killing the old one. As Toyota used to say: Who could ask for anything more?

The CC system on this car is actually pretty sophisticated. I should really do a write up on it. I haven't because many guys don't use it. They like to be in control at all times but after another 20 years of driving they'll change that tune

 

[Piratetip]

Yup switch works good, LED still intact.
But that damn pin 3 is not switching to ground. AHH! Crap, I pushed that button a hundred times waiting for my DVOM to change. Nothing

Can we jump start it? :evil5: j/k

Thanks for the insight into these strange 1980's electronics. Appreciate it.

 

[Piratetip]

Picked up a new unit for cheap

 

[plaaya69]

I received the payment and it will be going out with usps.

Thanks.