Cranking not starting, No CPU (OBDII) Power

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Not sure what is going on, but here is what has happened: was driving and noticed that the voltage was low (9-10) volts and battery light was on. Couple minutes later, car died while driving. Restarted immediately and drove for several more minutes, voltage fluctuated from 10-12 volts. No loss of power. Died a couple minutes later. Will crank but won’t start. Scanguage has no power, don’t have 12 v at efi relay, efi relay seems to be testing fine but gonna replace you see if that does anything. Replaced fusible link. Really thrown by the loss of power to the scangauge. Not sure where else to look or what else to do to figure out what’s going on. Not sure what other info is needed to help diagnose
 

LandLocked93

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1) Batt voltage? If good,
2) Check voltage behind the fusible links - between the batt and first fuse box. If good,
3) What is your scan gauge powered by? What's the voltage on that wire? Is it fused?
4) What else doesn't work?
Sounds like a bad regulator on your alternator. They can be replaced, but some have found replacing entire alt is more cost effective for them.
 
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1) Batt voltage? If good,
2) Check voltage behind the fusible links - between the batt and first fuse box. If good,
3) What is your scan gauge powered by? What's the voltage on that wire? Is it fused?
4) What else doesn't work?
Sounds like a bad regulator on your alternator. They can be replaced, but some have found replacing entire alt is more cost effective for them.

1) Battery Voltage good, also tried jumping it too.

2) I’ll check here momentarily, just starting to mess with it again after towing it home 500 miles

3) The scangauge is plugged into the obdii port

4) Everything else seems to work. I’m not getting 12v at efi relay, which may be why ecu isn’t getting power?
 
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I have proper voltage at EFI relay and COR relay. Still no power to ecu based on scangauge not powering. How should I go about testing voltage regulator on alternator? What else should I be looking at?
 
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Fusible links would be the first thing to check/replace. Especially if you've been messing with the battery.


I replaced that with no luck. Really thought it was that at first too and had a spare in the back so through it on but didn’t change it.

Just pulled the alternator out, the wire is corroded, looks like something shorted and melted the wire, almost looks welded. So thinking my culprit is in there somewhere...just don’t know why it shorted
 

ppc

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If you have some type of short it needs to be corrected. With a short the new fusible links most likely immediately failed when attempting to start.
 

LandLocked93

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Just pulled the alternator out, the wire is corroded, looks like something shorted and melted the wire, almost looks welded. So thinking my culprit is in there somewhere...just don’t know why it shorted
Is the welding on the backside of the terminal connecting to the alt? The side closest to the alt case? The varying voltage suggests arcing events, resulting in the welded look you describe. And it sounds like it's been regularly arcing at lower intensity for a long time. You might have found the cause of the issue. I added 2 layers of stout heatshrinkwrap to the terminal. Fixed. Get the alt tested at an autoparts place (they do that yeah?) and address accordingly.
But re-reading your description of events - and addendums thereto, this 1 banana monkey would look for a known good used ecu for expediency sake and go from there. The YotaYard in Denver is a great place to check. 👍
 
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Is the welding on the backside of the terminal connecting to the alt? The side closest to the alt case? The varying voltage suggests arcing events, resulting in the welded look you describe. And it sounds like it's been regularly arcing at lower intensity for a long time. You might have found the cause of the issue. I added 2 layers of stout heatshrinkwrap to the terminal. Fixed. Get the alt tested at an autoparts place (they do that yeah?) and address accordingly.
But re-reading your description of events - and addendums thereto, this 1 banana monkey would look for a known good used ecu for expediency sake and go from there. The YotaYard in Denver is a great place to check. 👍

I may be tracking, not entirely sure, but the truck has started! See pictures below. Wire was badly corroded and terminal snapped off when removing. I cut wires back about 4 inches and spliced in some new wire. Heat shrinked everything, put a new terminal on (just copper battery terminal). Put a new alternator (shi**y parts store until I can get reman Toyota in mail), and now it’s running. Thinking I’ll have the one a pulled out tested but it snapped the threaded post off partly when removing nut. Hopefully it’s just a bad alternator and corroded wires leading to bad ground issues.

51B79278-C0F1-49C6-A061-8518D3164724.jpeg


446EC792-4A83-40A5-A956-D03769DA3627.jpeg
 
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I have a weird electrical issue, a few weeks ago I was driving and my 96 80 died and then restarted. Later that day it died and didn't restart. I had it towed home and tested it and looked like it wasn't getting fuel. I have put a new fuel pump in it a new EFI relay and a new fusible link along with some other relays, still no start. have noticed that there seems to be no power to the OBD, blower fan and headlights and maybe ECU. Any ideas would be appreciated.
 

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