Looking at a Haynes manual, it's the fuel pump relay and the oil pressure sensor.
Now I'm wondering if my recent work on the oil pressure sensor bared some wires or something...
Too dark and late tonight...I'll follow up on that in the AM.

 

OK...fuse # 10 on this '98 is for the PCM/VCM ignition, injectors, crank sensor and coil driver module...according to the owners manual.
Checking the Haynes manual again, and looking at (I hope) the right wiring diagram...#10 runs to the PCM.

I can see anything in the wiring that looks suspicious...so I guess I'll just run it (closer to home) and carry extra 20A fuses.
I don't like not knowing why it blew...it's not blowing now, and there was nothing going on at the time it blew to point at anything specific.

It has been leaking oil, so I check it often and had run about 100 miles, stopped and checked the oil, then went on my way and within 5 miles that fuse blew.

 

I am having a hard time following. Looking at the owners manual and the wiring diagrams, the ECMB fuse in the UHFB is for the ECM, fuel pump and oil pressure switch

Fuse #10 in the IPFB is for turn signals.

They are both 20A


George

 

I checked again, and yep...it's #10. It's right next to #16, so maybe that's what you're seeing?
And the manual says this is a 97'...am I barking up the wrong wiring diagram?

 

I was studying '98 as stated in your first post. I may have time to look at '97 later tonight.


George

 

I apologize for getting the year wrong. It's a 97', for sure. 4x4, auto trans.
Looking at the fuse list, #10 handles a lot of things.
It's going to be a troubleshooting challenge, because it's not consistent...this is the first time it happened, and it's running fine with a new fuse in it.

 

That's a tough problem because all of those things have to be in the circuit for the truck to run so they cant be removed. I would start off by checking all of the grounds for the modules. I can look up their location if you need it but look for all ground cable connections to the body around those modules and see if they are clean and tight. Beyond that it gets more complicated. One thing to do is check the power draw of each module and see if any of them are near the fuse limit. Next could be to check the injector coil resistance(s). Next would be an inline fuse one at a time for each component to see which one it is. This would require cutting and soldering. Last would be replacing with known good components but that's a brutal proposition given the modules involved.

Part of the problem here is that it may be intermittent and all of the current draws may be normal most of the time. Now that you know the fuse involved we can stop condemning the fuel pump.


George

 

Thanks George,
Yes...can't disconnect any of those systems and keep it running.
First step for me is to run it while I wiggle the wiring and hope it reveals itself.
I hope to pull my little camping trailer about 30 miles later this week, and I'm worried. I hope the trailer brakes don't fail if/when fuse #10 blows...I'm hoping that circuit won't be affected, My read of the wiring diagram doesn't show that it will...but I don't trust my skill on that.
What do you think, George?

 

I see that the '97 does not have a dedicated brake/stop output (usually lt blue) in the trailer wiring provision so are you talking about electric brakes or mechanical surge brakes on the trailer? Electric brakes would have to interpret simultaneous signals on the left and right turn bulbs (yellow and dk grn) or you would need an aftermarket wire run to the brake pedal switch output.


George

 

They are electric brakes, that operate on inertia. There is no tie-in with the brakes on the truck, except for the brake lights. The controller has a fused, dedicated power source from the battery and runs to the braking system on the trailer. The stop/turn/running lights are on the existing (factory) tow package. The new trailer connector has a connector for the "flat" connector it came with, and the brakes and charging power are run separately.