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The mkiv Supra Owners Club

I've reached that age, time to talk about my MKIV


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Posted (edited)

Hello good day

I am a proud owner of a 94 JDM Supra, Automatic Twin Turbo in Toyota's lovely 199 Alpine Silver
(OK I appreciate it's a common base coat though it's still nice!)

She has been in my possession since around 2010 and is below 60,000 miles
From what I can tell it's stock except for 

  • Work Equip alloys
  • Auto watch alarm
  • HKS dragger exhaust

Good things about it

  • It is a MKIV Supra ...
  • Interior is superb, still has it's factory smell
  • Clear coat is impressive, where there's no stone chips (collective sigh here everyone..I know, but something about a respray makes me feel like I am covering over the original..)
  • Electronics have always been good(though see my recently developed issue below)
  • Engine has been seemingly strong for it's age
  • 18/20 MOTs pass record(one had exhaust leak on factory exhaust and other was thinning tire tread)


As an American living here in England, my choices on what vehicle to have as a hobby was different than back home of course. And the concept of drag racing takes on a different meaning when you're on B-roads with aggressive crowning and massive dips and potholes from semi trucks warping the roads over the years

So the idea of grabbing a powerful street car with Automatic transmission and not having any wide flat place to rip it, wasn't as appealing as it could have been
That said I had always been a fan of Toyota engineering and pursued a Supra for some years before purchasing
When this one came up I felt it was a good base platform whether to keep stock as is, and enjoy it in the purest form, or to modify later on



The car does have it's own share of issues

  • As mentioned before, I don't love parts of the paint due to the chips, though only I seem to notice them..somehow
  • The underside has typical surface rust, such as on control arms, suspension, diff etcetc.  - this does not extend to the body
  • The ECU might be damaged? This past year or two I started getting error 89 and 63 TRAC each time I take it out of cold weather storage[garaged]. I get the dread blinking TRAC, MANU, OverDrive lights and the transmission doesn't always go into Overdrive, nor does it respect L drive 


I've now had the vehicle for half the time I have been in the country and decided it's time to take it's ownership a little more seriously
And..gentlemen I am now passed the blood brainer barrier age of 40, which totally influences my decision making differently 

Plans for this year

  1. Have the rust removal/prevention work done( I am speaking to a professional team who do clean and spray and seal services)
  2. Try to solve the electronic error codes (not to name drop though Chris Wilson has kindly been giving me some wisdoms and anecdotes. He's willing to look over it and check solenoids and etc)

Plans for next year

  • Continuation of above as needed
  • Full fluid change(sans the transmission, if it's clean from sample testing, I really don't to flush it unnecessarily)
  • Possibly be convinced to get some of it resprayed? Unless someone can show me it's better to get the chips restored section by section


That's it from me.
When I am eligible to post on the sale/buy forum section, I'll be asking whether anyone has an interest in selling either the stock auto ECU main or ECU TRAC
(or maybe have a spare I can put a down payment/collateral on and borrow to test)
I believe the codes are 

And if anyone can recommend some kind, passionate and knowledgable automotive mechanics, electricians or repair in the  East Anglia area, please do
Also happy to move my electronics issue to fault finding thread though I appreciate the subject matter has been done to death
Though if it is ECU, my query then would be less about the fault finding itself and more how is the best way to proceed  

- Buy as many used ECUs you can find, fit them and hope it works?

- Buy an after market (though I am told there never was any good aftermarket ECUs for the Auto TT

- something else?


Edited by JusticeTT (see edit history)
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Posted (edited)

While I am waiting on this to be hopefully approved by moderator..


I meant to include the following in my plans for next year, which is to do a belt and pulley system check/replacement

Also..part codes I listed on the ECUs... ignore that with prejudice! Not sure why I listed those
Image attached is from my boxes and they seem to line up with what's been posted prior

What I find curious is
A) 89661-14491  and  89661 -14490 

Are listed as the Engine ECU according to the Supra forums via Ian and some others

I presumed '90' as pre facelift and '91' was post facelift? Though while mine is definitely a prefacelift vehicle, yet my part ends in 91...


B) For the throttle ECU, they have also listed a code in some part catalogues of 89670-14050 meanwhile mine is  89671-14010
I mention this as wondering whether that one can also work, possibly an alternative model units in event I cannot find exact replacement

C) See that tape job on the Engine ECU. It's a soldered of a red wire that runs around back and into the console area and a peach/pink wire. I believe this might have something to do with the speed conversion to MPH?
In one of the images right at carpet's edge you can see a pink piece of wire, looks like left over when whomever did the work
I took the tape off gently and found it's soldered - can't tell the quality though it's together for sure. I've issued new tape and closed it all up

Update on the car's electrical behavior


Wweather warmer today for certain. Started the car, no flashing lights. Manu mode responds instantly when pressing it.

Out for a drive, results are :

- Low is not respected, car's lowest gear is still 2nd

- Manu seems to be respected otherwise. Example : while it's in 2nd won't shift up and similarly, drive won't go to Overdrive

- Overdrive seems to be working more consistently (would need more testing time). Pressing the button on off get's near instant response from the transmission 



I really am thinking there's a temperature element to all this, given my previous experience about the storage period where this only seem to began after cold months storage and then symptoms start to cease with warmer climate




Edited by JusticeTT (see edit history)
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Interesting. I’ve just gone big single turbo and I have code 89, a flashing O/D light, no MANU mode and overdrive will only engage when the car is up to a sensible temperature. James at Cribbs Speed Shop and Mike at SRD have gone through everything, tried multiple ECU’s and TRAC ECU’s but to no avail!

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  • 4 weeks later...

Still on the hunt for a spare working ECU to test with ; in meantime small followup in among my transmission issues

I've done another code test recently and found it's no longer reporting 89 which was 


However the code 64  is still present

Both the above chart and the below chart indicate it's a type of short circuit or issue with a solenoid valve 3
I am trying to find some diagrams/imagery on it

A thing of note is the above states "Malfunction with code No. 64 is not indicated to the driver. But the code is stored in the memory"
I am not certain how to interpret that. Does it mean by "indicate" that the code will not appear when doing a code diagnostic and watching the blinks, if that's the case then what is the six + four blinks I am observing related to then?

Or does it mean that unlike other codes which give a warning light - hazard, abs, oil, engine etc, this one will not have it's own designated symbol?
Provided the latter was true, then would that not apply to error 63 and 62 for the other solenoid valves?




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