control chip issue?

redsupra · 04-13-2011, 06:14 AM

Hi, hopefully I've found the best Supra resource on the net. There seems to be some very knowledgeable people here.

I'm needing some assistance to solve an ongoing nagging issue with my Supra. It's a MK4 1993 (red, sort of), twin turbo, automatic. I've had this vehicle since Dec 2001 and absolutely love it to bits, despite its foibles as it ages.

I'll describe the main problem and then what I've "discovered" through searches on the net to date. Rememnber this has been an issue for some years and hasn't affected the car to any extent.

O/D light flashes sometime after start (might be immediate, might be after a little while). Front spoiler is inoperable. Cruise control is inoperable.

Now, when this first started I looked up the flashing O/D and one resource said it could indicate a transmission problem. However another indicated something else and the flash rate didn't match the one for the transmission but appeared to highlight a problem with the speed control chip.

Ok. Now, I'm no car techo, I do software, but further research seemed to confirm this. Apparently the front spoiler and the cruise control are governed by this chip and is symptomatic of the general issue (along with the flashing O/D light).

As I understand it this "speed control" chip can have an issue with a loose weld/solder on a contact point and thus the connection and functionality fail (probably indicative of the time that the O/D light starts when sometimes the contact is ok and then breaks and the light flashes).

When this first started, it was very intermitent and I noticed the front spoiler worked intermittently too. I rarely used the cruise control, but tried it a little while back and it does not work any longer (when it used to before all this started).

So, question is: is this analysis correct and how do I go about fixing it? No one (Toyota or my performance car mechanic) seems to know. If I could ascertain the location of this unit and the method to fix it I could probably do it myself (I'm handy with tools, soldering etc). If not myself then get the info to someone who can do it.

Any and all assistance would be greatly appreciated.

Now apart from needing a new paint job, rims, sound system, bushes and possibly some bearings in the fanbelt wheels, all is just fine!

cheers,

Chris

pwpanas · 04-14-2011, 01:07 AM

Quote:

Originally Posted by redsupra

Hi, hopefully I've found the best Supra resource on the net. There seems to be some very knowledgeable people here.

I'm needing some assistance to solve an ongoing nagging issue with my Supra. It's a MK4 1993 (red, sort of), twin turbo, automatic. I've had this vehicle since Dec 2001 and absolutely love it to bits, despite its foibles as it ages.

I'll describe the main problem and then what I've "discovered" through searches on the net to date. Rememnber this has been an issue for some years and hasn't affected the car to any extent.

O/D light flashes sometime after start (might be immediate, might be after a little while). Front spoiler is inoperable. Cruise control is inoperable.

Now, when this first started I looked up the flashing O/D and one resource said it could indicate a transmission problem. However another indicated something else and the flash rate didn't match the one for the transmission but appeared to highlight a problem with the speed control chip.

Ok. Now, I'm no car techo, I do software, but further research seemed to confirm this. Apparently the front spoiler and the cruise control are governed by this chip and is symptomatic of the general issue (along with the flashing O/D light).

As I understand it this "speed control" chip can have an issue with a loose weld/solder on a contact point and thus the connection and functionality fail (probably indicative of the time that the O/D light starts when sometimes the contact is ok and then breaks and the light flashes).

When this first started, it was very intermitent and I noticed the front spoiler worked intermittently too. I rarely used the cruise control, but tried it a little while back and it does not work any longer (when it used to before all this started).

So, question is: is this analysis correct and how do I go about fixing it? No one (Toyota or my performance car mechanic) seems to know. If I could ascertain the location of this unit and the method to fix it I could probably do it myself (I'm handy with tools, soldering etc). If not myself then get the info to someone who can do it.

Any and all assistance would be greatly appreciated.

Now apart from needing a new paint job, rims, sound system, bushes and possibly some bearings in the fanbelt wheels, all is just fine!

cheers,

Chris

I'm mostly only knowledgeable about the US spec MKIV, which doesn't have a speed control chip. That said, many of the solder joints on the Mkiv are known to go bad...usually in the dash. Personally, I suspect the problems with the dash solder joints are due to flexing of the dash panels as they are repeatedly removed and reinstalled with aftermarket gauges, stereo components, etc. Within the engine bay, solder joints going bad is rare. That said, I can't say it's entirely unlikely because of that problem in the dash area. I believe it would be worth disassembling the speed control ecu area and using a multimeter to test the solder joints. To aid you in this, I'd strongly recommend you pick up a copy of the Toyota Supra Repair Manual for your version of the MKIV.

Also, have you considered installing a bypass to your speed limiter?
http://www.billetdesign.com/hks-spee...-pr-19277.html

Lastly, this may help:
http://mkiv.supras.org.nz/techo.htm#SPEED_LIMITER

redsupra · 05-23-2011, 04:11 AM

Ok, so I spoke to my mechanic about the issue and he searched through a stack of business cards and pulled a couple of names that might be able to help. One of the guys used to deal with racing supras and knows about the issue and used to fix them all the time, and yes as you said pwpanas, soldered joints going bad in the dash

However he doesn't do that work anymore so will have to try him for info on where and what to do. I have another guy to call that has done supra dashboards and may also be able to help. It's not a priority, but needs to get fixed in the near future.

04-13-2011, 06:14 AM	#1
redsupra Stock Join Date: Apr 2011 Location: Melbourne Posts: 8	control chip issue? Hi, hopefully I've found the best Supra resource on the net. There seems to be some very knowledgeable people here. I'm needing some assistance to solve an ongoing nagging issue with my Supra. It's a MK4 1993 (red, sort of), twin turbo, automatic. I've had this vehicle since Dec 2001 and absolutely love it to bits, despite its foibles as it ages. I'll describe the main problem and then what I've "discovered" through searches on the net to date. Rememnber this has been an issue for some years and hasn't affected the car to any extent. O/D light flashes sometime after start (might be immediate, might be after a little while). Front spoiler is inoperable. Cruise control is inoperable. Now, when this first started I looked up the flashing O/D and one resource said it could indicate a transmission problem. However another indicated something else and the flash rate didn't match the one for the transmission but appeared to highlight a problem with the speed control chip. Ok. Now, I'm no car techo, I do software, but further research seemed to confirm this. Apparently the front spoiler and the cruise control are governed by this chip and is symptomatic of the general issue (along with the flashing O/D light). As I understand it this "speed control" chip can have an issue with a loose weld/solder on a contact point and thus the connection and functionality fail (probably indicative of the time that the O/D light starts when sometimes the contact is ok and then breaks and the light flashes). When this first started, it was very intermitent and I noticed the front spoiler worked intermittently too. I rarely used the cruise control, but tried it a little while back and it does not work any longer (when it used to before all this started). So, question is: is this analysis correct and how do I go about fixing it? No one (Toyota or my performance car mechanic) seems to know. If I could ascertain the location of this unit and the method to fix it I could probably do it myself (I'm handy with tools, soldering etc). If not myself then get the info to someone who can do it. Any and all assistance would be greatly appreciated. Now apart from needing a new paint job, rims, sound system, bushes and possibly some bearings in the fanbelt wheels, all is just fine! cheers, Chris

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05-23-2011, 04:11 AM	#3
redsupra Stock Join Date: Apr 2011 Location: Melbourne Posts: 8	Ok, so I spoke to my mechanic about the issue and he searched through a stack of business cards and pulled a couple of names that might be able to help. One of the guys used to deal with racing supras and knows about the issue and used to fix them all the time, and yes as you said pwpanas, soldered joints going bad in the dash However he doesn't do that work anymore so will have to try him for info on where and what to do. I have another guy to call that has done supra dashboards and may also be able to help. It's not a priority, but needs to get fixed in the near future.