SC- 1st Gen (1992-2000)

ECU fried

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Old 12-21-23 | 11:17 AM
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Default ECU fried

Hello all, I'm new here and this is my first post because I am in need of some help. For reference I have a 1995 sc300. I had my fuel pump ecu go out. I did the 12v mod but I believe I did it incorrectly. My car ended up losing overdrive and eventually wouldn't start because the main ecu wouldn't give power to the fuel pump. I had the main ecu repaired and the car started and ran great but the next day it wouldn't start, (same problem no power to fuel pump). The picture below is the fuel pump ecu bypass but I did mine differently. Instead of jumping them like in the picture I cut the same wires below the connector and soldered them together and then plugged the harness back into the fuel pump ecu. I'm now looking at videos and everyone who has done the mod doesn't plug the connector back into the the fuel pump ecu. Is this what is frying my ecu? My current condition is crank no start, fuel pump isn't getting power and the check engine light isn't illuminating during bulb test.


Last edited by mlthill; 12-22-23 at 02:48 PM.
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Tallyhoe (12-21-23)
Old 12-21-23 | 07:58 PM
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Originally Posted by mlthill
Hello all, I'm new here and this is my first post because I am in need of some help. For reference I have a 1995 sc300. I had my fuel pump ecu go out. I did the 12v mod but I believe I did it incorrectly. My car ended up losing overdrive and eventually wouldn't start because the main ecu wouldn't give power to the fuel pump. I had the main ecu repaired and the car started and ran great but the next day it wouldn't start, (same problem no power to fuel pump). The picture below is the fuel pump ecu bypass but I did mine differently. Instead of jumping them like in the picture I cut the same wires below the connector and soldered them together and then plugged the harness back into the fuel pump ecu. I'm now looking at videos and everyone who has done the mod doesn't plug the connector back into the the fuel pump ecu. Is this what is frying my ecu?
LOL, that's my picture right there, and I do post on the Tundras forum and that is my post, unfortunately that jump fried and left me stranded at a gas station and had the cops called on me, they thought I stole the car since I started taking it apart at the pump. I plugged it back in and remains plugged in as my pump is getting power..... Eitherway, Try this vid right here, I used some of it to troubleshoot my issue, hope this helps some.
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mlthill (12-22-23)
Old 12-22-23 | 10:16 AM
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Originally Posted by Tallyhoe
LOL, that's my picture right there, and I do post on the Tundras forum and that is my post, unfortunately that jump fried and left me stranded at a gas station and had the cops called on me, they thought I stole the car since I started taking it apart at the pump. I plugged it back in and remains plugged in as my pump is getting power..... Eitherway, Try this vid right here, I used some of it to troubleshoot my issue, hope this helps some.
https://youtu.be/f4No-8MneWU?si=QsFkfc7HQujIrzsB
Thanks for that video I haven't seen that one yet. Crossing my fingers i can figure this out
Old 12-22-23 | 06:48 PM
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sounds like your main ecu is going bad
Old 12-22-23 | 07:01 PM
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Originally Posted by Ali SC3
sounds like your main ecu is going bad
I had it repaired and it started and ran great for a day but the next day it wouldn't start I think it got fried but dont know why. I dont want to spend another 200 just to get fried again
Old 12-23-23 | 02:19 PM
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Originally Posted by mlthill
I had it repaired and it started and ran great for a day but the next day it wouldn't start I think it got fried but dont know why. I dont want to spend another 200 just to get fried again
Any progress?? If you're frying your ECU inspect the grounding points or even an ECU fuse additionally swap the HVAC relay with the fuel relay, I do believe they're the same.
Old 12-23-23 | 02:26 PM
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Originally Posted by Tallyhoe
Any progress?? If you're frying your ECU inspect the grounding points or even an ECU fuse additionally swap the HVAC relay with the fuel relay, I do believe they're the same.
No luck so far. I confirmed the efi relay and fuse are good, im going to check the ground and power for the ecu next. I'd like to open it up and confirm it's fried again but it voids the warranty from the place I had it rebuilt.
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