Electrical short

Joined
Jul 4, 2020
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Location
idaho
1992 Fj80 I have an electrical issue could use some help...
Turn ign on 15amp #9 ign/ecu fuse pops
Activate CDL swtch in dash 30 amp #14 Diff fuse pops
Shift lock does not work (have to use bypass button, but will work with new 15amp ign/ecu fuse if you time it right) Disconnected harness to shift lock solenoid and computer 15amp fuse still pops.
CDL works in 4LO with shifter only (with new fuse)

New parts installed after discovery
Fusible link
Ignition wire assembly.

any help knowledge would be appreciated. working thru FSM EWD but I not the greatest with electrical.
 
Joined
Dec 8, 2006
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just spit balling, check that your o2 sensor wiring hasn't melted and shorted. common ecu short.
I believe the OP is referring to the ECU/IGN fuse in the fuse panel by the driver's left knee, not the EFI MAIN fuse in the under hood fuse box.
ECU/IGN supplies power to the following:
Cooing fan ECU
Cruise Control ECU
Speed sensor
Shift lock ECU
 
Joined
Jul 4, 2020
Messages
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Location
idaho
I believe the OP is referring to the ECU/IGN fuse in the fuse panel by the driver's left knee, not the EFI MAIN fuse in the under hood fuse box.
ECU/IGN supplies power to the following:
Cooing fan ECU
Cruise Control ECU
Speed sensor
Shift lock

I believe the OP is referring to the ECU/IGN fuse in the fuse panel by the driver's left knee, not the EFI MAIN fuse in the under hood fuse box.
ECU/IGN supplies power to the following:
Cooing fan ECU
Cruise Control ECU
Speed sensor
Shift lock ECU
That is correct. fuse panel by left knee. Where is the engine bay cooling fan ecu/timer located? I found it pass side kick panel. Still working on short.

thanks
 
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Joined
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That is correct. fuse panel by left knee. Where is the engine bay cooling fan ecu/timer located? I found it pass side kick panel. Still working on short.

thanks
Page 122 in the Toyota EWD.

1669218259983.png
 
Joined
Jul 4, 2020
Messages
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Location
idaho
Thanks for the EWD.
Unplugged Cooling fan ECU/timer turn on power 15amp breaker holds. Started truck and 15amp breaker trips. shut power off, reset breaker turn on power but dont start engine and breaker trips.

unplugged speed sensor turn on power breaker holds, turn on CDL in dash 15amp breaker trips.

I was hoping to find problem by unplugging connections that run thru 15amp ign/ecu fuse. Breaker would hold until either engine is started or CDL switch in dash is actuated.

Going to pull CDL switch and bench test with meter.

After that I will start tracking wires....

With CDL dash push button switch in on position there is no continuity between pins 10 and 8. 10 and 7 with switch off there is continuity.

Replaced CDL Switch with hazard switch turned CDL on 30amp diff fuse melts?
 
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Jan 5, 2017
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Charlotte, NC & Alexandria, VA
Before you go looking for the Easter egg in your dash, check for some twit piggybacking off your harness somewhere. Aftermarket accessories, or "professionally installed" stereos are a possible culprit.
 
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Messages
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Location
idaho
Before you go looking for the Easter egg in your dash, check for some twit piggybacking off your harness somewhere. Aftermarket accessories, or "professionally installed" stereos are a possible culprit.
No such devices. Completely unmolested bone stock rig. Got it cheap and its going to cost me a fortune :p. Tr.ying to make it reliable while I work on finding a mercedes 606 to replace 3fe. I am using it as a daily.

Had to divert attention to replacing rear wheel bearing, leaking seals, and soaked and swelled brake shoes.

Back to short...

Replaced Fusible links and ignition because they were in scary shape.

1992 fj80 3fe bone stock. Truck runs and drives well.

2 issues I am working on now
1 - 15amp ign/ecu Ignition fuse pops with key turned to accessory or if you unplug components that run thru fuse 15amp fuse it will not pop until key turned to start position.

2 - 30 amp CDL diff fuse will pop when cdl dash switch is activated bench tested dash switch 10-7 pin switch off continuity 10-8 pin switch on no continuity. Cdl will operate when shifted to 4lo with shifter.

Side note When on an elk trip in Wyoming cold morning the starter was stuck in the engaged position for about 20-30 seconds. only did it once.
Cold mornings in driveway it sounds like starter is hanging up (spinning) for a few seconds? Anyone come across this could a bad starter relay be shorting my fuse.

Today I will be tracing wires with meter

Thanks again for any input
 
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The starting circuit is fairly sparse. I don't have the EWD in front of me, but I'd get one and walk through it. There is a Chassis a & Body manual (courtesy of @TRAIL TAILOR) in the Resources section. It should have the EWD at the end.

Starter problem definitely sounds like a stuck solenoid. Time to get a rebuild kit.
 
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Joined
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idaho
update on 15amp ECU/IGN fuse.
Narrowed short down. If I let truck idle for a while I can hear shift solenoid make noise and then I am able to shift out of park to Drive without stepping on brake pedal and you cannot hear solenoid actuate.
OR
Before solenoid makes noise you can shift from park to reverse and 15amp ECU/IGN fuse will blow?
It will not blow fuse if you shift to drive?

Is there a bench test for Shift solenoid / shift solenoid ecu?
I looked thru factory service manual couldnt find one.
I do not have the Factory EWD.

Thanks in advance for any input
 

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