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Stock Twins King
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When it comes to Auto Supra's I know very little actually. So I acquired a 1994 RHD TT Auto (RHD) about 2 months ago. I was driving it and thought it was unusual that the O/D OFF light wasn't illuminating. Go to find the bulb was broken. Replaced the bulb and now when I have O/D OFF pressed it flashes/blinks and doesn't go away. Read how to get the code by jumping the TEi-E1. That is how I got the Code 89. What i have not tested is the Cruise operation. I probably need to do this as it is part of the equation I am sure. So is the same code/errors as all the other issues I read about? Where you can touch up solder points or reroute pink ODO wire, etc? or is this all about the TRAC as the code refers too?

One last issue. When I press the MANU the light does not illuminate next to the O/D light. And it isn't the bulb. I have not gone too much further to check simple issues like a broken switch wire, bad switch yet, but was wondering if this is related or MANU is altogether different issue.
 

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Has it got a speed speed signal convertor fitted? Cheap/poor quality ones are renown for causing issues for the JDM Supra. Also take a look at the traction control fuse & ECU.

E2A

If it isn't any of the above I would concentrate your search around the TPS and the throttle motor, their respective wiring, set up and freedom of movement of the motor and check for a worn or noisy carbon track on the TPS.

You could also try removing the stepper motor, cleaning it and refit it. Then undo the screws that hold your SUB throttle pos sensor (dont fully remove them just loosen them) lift the sensor to the highest position you possibly can and then reset the ECU.
 

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Stock Twins King
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Discussion Starter #3
Has it got a speed speed signal convertor fitted? Cheap/poor quality ones are renown for causing issues for the JDM Supra. Also take a look at the traction control fuse & ECU.

E2A

If it isn't any of the above I would concentrate your search around the TPS and the throttle motor, their respective wiring, set up and freedom of movement of the motor and check for a worn or noisy carbon track on the TPS.

You could also try removing the stepper motor, cleaning it and refit it. Then undo the screws that hold your SUB throttle pos sensor (dont fully remove them just loosen them) lift the sensor to the highest position you possibly can and then reset the ECU.
Trac FUSE-OK. No speed converter installed. I reset EFI fuses no help.

What is E2A?

I also just noticed that when I pushed in the Slip control, the idiot light went on, but when I go and push slip again (to turn off) the idiot light would not go out.

I will mess around with the TPS stuff later.

Do you think this issue could be related to the ODO cold solder? I could pull that and touch up all of the solder areas to see.... Something tells me Code 89 is something all together different... I will check the MANU switch here soon as I need to replace the shifter bushings.
 

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I just had this issue with my 95 na auto of the o/d off light flashing. The cruise control would not work also. The odometer was counting miles slowly and that was the culprit. I ordered a new odometer from Stan at Elmhurst and it fixed the problem. I tried to send the odometer to bitshftr for repair first but usps lost it. I would definitely try the odometer repair and see.
 

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Stu, like you mentioned you can touch up the solder on the back of the odometer, or you can cut and splice the pink wire onto the blue/red striped wire. This is very common. The VSS doesn't make it through the odometer.

ODflashingmod.jpg
 

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Do you think this issue could be related to the ODO cold solder? I could pull that and touch up all of the solder areas to see.
That would be another place to check if there isn't a signal fudge fitted :bigthumb:

E2A = Edited 2 (to) Add. Apologies, it is a terrible habit :)
 

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OP. I recently acquired a 94 auto TT from a ***ahem*** dealer in IL and I also had a bunch of issues that I have finally resolved over the last 4 months. (Including a slow speedo solved by Stu.)

I also had a flashing Trac and overdrive after I fixed my true overdrive flashing light issue. My Trac and overdrive flashing was caused by a faulty main ecu. (Swapped out for a used one)

You may be dealing with multiple issues be careful about just following the mkiv splice and bypass procedure as it may not be your cause.

On the overdrive flashing issue. I would open up the auto shifter panel and look for the blue connector plug from the auto shifter. As both your overdrive and manu switches are not working I suspect the connector or wires in that area (they share the same connector). disconnect the connector and test for continuity....In both cases. (Factory service manual)

In my case, some jackass had cut the wires in the auto o/d handle and without testing I couldn’t tell they had done so. I assume they had an aftermarket shifter on there and were too lazy to reverse it prior to selling.

Good luck.
 

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Stu, (and everyone else)… I just went through this problem. I spent 60-70 hours trying to troubleshoot, splicing wires, tracing VSS, changing O2 sensors, etc. I found a Lexus form and had an "ah-ha!" moment. Per Lexusforums… 1990 Toyota ECUs were manufactured with poor capacitors. Save yourself some time and open up the main ECU. (It's sealed with adhesive. Use a heat gun to soften glue.) You will likely see leaking capacitors causing the 89-code. (Which is trac to ECM comm failure). I purchased new radial capacitors and had them all replaced by an electronic shop. The problem has gone away. I have a list of all the caps and my purchase list from Digikey if you need it.

95 USDM Auto TT
 

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Stock Twins King
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Discussion Starter #9
Stu, (and everyone else)… I just went through this problem. I spent 60-70 hours trying to troubleshoot, splicing wires, tracing VSS, changing O2 sensors, etc. I found a Lexus form and had an "ah-ha!" moment. Per Lexusforums… 1990 Toyota ECUs were manufactured with poor capacitors. Save yourself some time and open up the main ECU. (It's sealed with adhesive. Use a heat gun to soften glue.) You will likely see leaking capacitors causing the 89-code. (Which is trac to ECM comm failure). I purchased new radial capacitors and had them all replaced by an electronic shop. The problem has gone away. I have a list of all the caps and my purchase list from Digikey if you need it.

95 USDM Auto TT
Well having the list will save me time with a magnifying glass writing them all down. Not my first rodeo here on Cap replacements. Because this Code 89 is so TRAC orientated I will try the caps swap. I mean, maybe the TRAC ecu is not even in the car or unplugged. I will look while I am removing the ECU.

I have to also see why the MANU button is INOP as well. I know it isn't the bulb as I tested it when I replaced the ODO bulb.
 

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True... if the the whole TRAC ECU is missing, then that's a whole other issue!

Here ya go. This was from my 1995 USDM JZ80 Automatic Transmission ODB 1 ECM:
Top board... C 705 - 15uF 35V. Bottom board... C105 - 100uF 10V, C118 - 220uF 10V, C115 - 100uF 10V, C622- 47uF 63V (mine leaking), C820-10uF 50V, C-111 10uF 50V (another leaking), C810 - 47 uF 63V.

Here is my order of low ESR caps from Digikey. (I ordered one extra of every type.)

EKZE500ELL100ME07D Quantity Price Price
565-1702-ND
CAP ALUM 10UF 20% 50V RADIAL 3 0.3 $0.90


EKZE630ELL150ME11D Quantity Price Price
565-1718-ND
CAP ALUM 15UF 20% 63V RADIAL 2 0.3 $0.60


EKZE101ELL470MJC5S Quantity Price Price
565-1734-ND
CAP ALUM 47UF 20% 100V RADIAL 3 0.67 $2.01


35ZLH100MEFC6.3X11 Quantity Price Price
1189-1300-ND
CAP ALUM 100UF 20% 35V RADIAL 3 0.3 $0.90


UHW1H221MPD Quantity Price Price
493-6817-ND
CAP ALUM 220UF 20% 50V RADIAL 2 0.84 $1.68

For those who may have the same issues with flashing O/D 89 code and MANU buttons not working and other phantom ecu codes, replacing all of the capacitors may resolve the issue. Over time the fluid inside the capacitor may dry up, although the capacitor looks fine, it will not work properly. (Some specifications state the useful life of these types of capacitors is only 10-15 years!) They may also leak acid onto the circuit board. If they do, make sure to clean up the board and inspect the tracers for continuity. It's best to have a local electronics repair shop to make the replacements because they (should) have techniques to remove the caps without damaging the surroundings components/connections and can use microscopes to check the tracers. It is VERY tedious work and while I have an electrical engineering degree, I am glad I handed it off to a shop to make the repairs.

I've only driven the car a couple hours since the repairs, but the 89 code went away and everything seems to be operating and shifting normally. Now I wonder if I should "unsplice" my pink VSS wire behind my speedometer and see if my cruise control is also working normally.
 

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Now I wonder if I should "unsplice" my pink VSS wire behind my speedometer and see if my cruise control is also working normally.
It won't. That problem is not rooted in the ECU. The odometer has some very very fine traces on the board, with super-small solder joints that were done by a very precise robot. One or more of them have gone cold. You can't resolder those joints by hand, unless you're Ant Man.
 

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Stock Twins King
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Discussion Starter #14
@Stu,

Any further update?
I am waiting for someone to chime in on the ability to remove the bushing bolt w/o having to do anything under the car. I am down to the main floor pan plate and haven't removed the 4 bolts yet to raise the assembly yet
 

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It won't. That problem is not rooted in the ECU. The odometer has some very very fine traces on the board, with super-small solder joints that were done by a very precise robot. One or more of them have gone cold. You can't resolder those joints by hand, unless you're Ant Man.
My cruise control issues, O/D code 89, false code 24 and TRAC OFF, and MANU OFF all started about the same time. Many systems, you know, (VSS, TRAC, throttle pos sensor) talk to each other in the ECM with "system logic". All my issues were remedied by the new capacitators. I thought it was odd. I wondered about the signal shaping that actually takes place in the odometer circuitry... and why is the uncorrected signal (spliced VSS) still clean enough to feed information to the ECM.

Yes, I have had solder-joint issues with my speedo in the past. I fixed some of the larger, more visible solder breaks many years ago. You are correct about the breaks in the tracers tiny tracers. I have squirrel hands, but not ant hands!!!!
 

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Stock Twins King
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Discussion Starter #17
My cruise control issues, O/D code 89, false code 24 and TRAC OFF, and MANU OFF all started about the same time. Many systems, you know, (VSS, TRAC, throttle pos sensor) talk to each other in the ECM with "system logic". All my issues were remedied by the new capacitators. I thought it was odd. I wondered about the signal shaping that actually takes place in the odometer circuitry... and why is the uncorrected signal (spliced VSS) still clean enough to feed information to the ECM.

Yes, I have had solder-joint issues with my speedo in the past. I fixed some of the larger, more visible solder breaks many years ago. You are correct about the breaks in the tracers tiny tracers. I have squirrel hands, but not ant hands!!!!
This is good to hear as I receive the caps tomorrow from Digikey. I have not attempted to clean up solder on the ODO MB yet. I will wait to see how the caps turn out first. I have touched up maybe a dozen ODO boards for others in the past but I guess I never heard back if this ever fixed there issues. One note...I did not get that Code 24. Just 89.
 

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Yup, that one is pretty bad! I would suspect the tracers were also damaged from that leak. Were you able to view that area with a microscope or magnifying glass?
 

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Stock Twins King
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Discussion Starter #20
Yup, that one is pretty bad! I would suspect the tracers were also damaged from that leak. Were you able to view that area with a microscope or magnifying glass?
All areas were clean and no paths missing. However, that picture was the worst of them. And I really couldn't see if the path was compromised or not. If you look at all the black goo under that cap, once cleaned
there was missing green soldermask down to copper. But it didn't look like the contact patch was gone....but really I cannot tell. I may pull it out again and do a continuity test.

NO DOUBT something was not working in the ECU with that Cap not even there.
 
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