Electrical issues.

Hey folks. I have a 17 trd sport 4x4 with 145k on the odometer.
Recently on a road trip my MIL came on for a mass airflow sensor circuit code. I replaced the sensor and it didn't fix the issue. On the same trip my auto headlight light sensor threw an open circuit code. My door locks and overhead cabin lights no longer work unless the vehicle is running. The remote on both sets of keys never work at all to unlock the doors but the push button start still functions fine. I checked all fuses and found the ecu no.3 10 amp was blown. As soon as I replaced it it blew again. Multimeter verification yielded a short to ground somewhere. At this point I'm stumped. Any ideas?

 

I'll have to look what all is on that fuse but have you added anything or had any work done to the truck recently?

 

Additionally inspect for rodent damage

 

I'm looking OP.
As of now, I've only found that it goes to the Body ECM and Combination meter.
But I am still looking.....Still have a lot more to look through.

 

As of now, all I have found to isolate the circuit would be the 1F connection.
Which I suspect is at a fuse box. I don't have the plug locations for a 3rd Gen.

Best I have found so far is that power goes through the short pin, to the ECM No.3 Fuse, then to the BCM and Combination meter.

An only one place to split the circuit to help identify what direction to go.

Going to need Dm93's help a lot here.
I'm limited on my end. Pretty much limited to Overall Wiring Diagrams on my side.

 

I'll have a look when I get to my desk.
Looks like the OP posted and left, hopefully they come back.

 

I recently had the engine replaced about 8k miles ago. Long story. The only mods I think would be relevant is aftermarket lighting.

 

OP are you referring to the ECU-B NO.3 fuse (10A) that's blowing?

 

Yes it's ecu b no 3

 

It feeds the Body ECU, Combination Meter, and Inner Rearview Mirror.

I suspect it's gona be a shorted wire between the fuse and Connector 1F of the Driver's side Junction Box/Body ECU.
Visual inspection goes a long way, since you said you had an engine put in look for any places the harness could be pinched or rubbing but don't move the harness just yet.

What I would do is put my 5 amp headlight bulb in place of the fuse and visually inspect/wiggle the harness coming from the fuse box while looking for the bulb to flicker or go out.

https://youtu.be/oKCLzf4va7M

 

Thankyou I will do that.

 

Here's the Driver's Side Junction Box connector views and pinouts if you need it, Power from the ECU-B No 3 fuse comes in on 1F Pin 15 (Red), goes to the BODY ECU which is internal to it and also exits on 1A Pin 18 (Pink) to the Combination Meter and 1A Pin 38 (Light Green) to the Inner Rearview Mirror.

 

Thankyou you have been extremely helpful. I'll see what I can find.