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post #1 of 5 Old 07-15-2015, 08:45 AM Thread Starter
 
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Sdl

No, not the usual issues but rather inconsistent illumination of the 1-4 SDL when starting. If the vehicle is cold, the 1-4 SDL along with all the others warning lights functions normally. However if the car is driven, at full operating temperature and then turned off the 1-4 SDL does not illuminate. If the car sits and cools off for an hour or so the SDL is back functioning normally. It would seem that something is either being affected by the engine bay temperature or is heating up from use. Another possibility may be vibration while driving but that seems a little far fetched since it 'repairs' itself when just sitting. I'm leaning towards the 1-4 ECU itself as being the problem and/or a plug-connector that is being affected by heat. Anyone have any insight as to where the problem may be? If all else fails, swapping the ECUs may help isolate the problem.
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post #2 of 5 Old 07-15-2015, 08:49 AM
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post #3 of 5 Old 07-15-2015, 12:41 PM Thread Starter
 
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Dave,

Those were my original thoughts also until I got thinking about the TCU/TC function. It's my understanding that the TCU just converts the millivolt signal from the TC to a higher voltage signal and sends this voltage signal to the ECU. The ECU in turn "decides" to flash or turn on the SDL if this voltage which corresponds to the TC temp. is outside of the permissible range. If my understanding is correct (and it may not be) it doesn't seem like the TCU has anything to do with the check engine/SDL/and other lights going through the "test" phase when turning the key on.

Now a wiring issue maybe another matter. Attempting to read the wiring diagrams in the WSM is difficult at best especially since the arrangement of the lights on the instrument panel is inconsistently shown and in places not in agreement with the actual layout on the car. I think I have traced the wiring from the 1-4 SDL back to the ECU connector on the diagrams but I'm not sure where some of the intermediate connectors shown on the diagrams are located. Since you have dropped the engine on your early build '95 which mine is also maybe you can help me locate the connectors. On the diagrams there looks to be one main connector for each engine bank in the harness between the ECU and the foot well fuse/relay panel. I did swap the ECU relays but that did not make a difference.
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post #4 of 5 Old 07-15-2015, 01:01 PM
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Bill,

TCU are known to fail, especially the older black potted ones. I just went thru this and replaced one with a new green potted unit and I believe my problem is gone. But, my 98 is OBDII and I was able to see a pending code which pointed me to 1 of 3 TCU's in a 96-99 car.

Sounds like you have a 95 so you only have 2, one for each CAT.
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post #5 of 5 Old 07-15-2015, 03:26 PM
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