EFI fuse blowing

I have a 99 V 4Runner that blew the EFI fuse yesterday and will immediately pop a new fuse with the key off. If I pull the relay and put a fuse in it will pop the fuse when the relay is put back. Can anyone offer suggestions on where to start looking? Thanks in advance

 

Start by testing the relay

It also powers the Circuit Opening Relay and the fuel pump circuit

Remove the circuit opening relay to check the fuel pump circuit for a short

As well as both O2 Sensors quite common for the harness to rub through or maybe melt I would bet on this but who knows

Had the vehicle had the Check Engine light on and were any codes pulled

 

Yesterday evening I switched the relay low and behold the fuse held, let it idle for about 10 minutes and went for a test drive, got about half a mile and the fuse went again towed home with a chain and back to square one. Tried every relay and they all did the same thing. I thought I had it licked and the relay was the problem. It seems to be something always hot because the key doesn't need to be on for the fuse to blow.

I see the circuit opening relay in the wiring diagram but not sure where it is located. If that relay is pulled and the fuse holds, that would indicate the fuel pump circuit?

Everything along the O2 wiring looks good but it does disappear in a few places that I cant see but can feel along and seems fine. I guess I could check for continuity from the ECM pins to the connector plugs?

The scan tool wont connect. I should have done it in the slim window it was running yesterday but since the ECM had been without power there were no CEL.

 

Loose connection in the fuse block or anyplace else causing it to Arc and draw to much current ??

Looking at the EWD for a 98 4Runner the Circuit opening relay should be below the fuse block on the left side

 

Anybody know where to get a pin-out diagram?

 

Need to find out what other circuits run off that one fuse and go from there .I think it was Mitchell has online wiring diagrams you can subscribe to monthly . I picked up Toyota
factory wiring diagram for an 05 rav4 on ebay so might want to check there also.

 

I have wiring diagrams even signed up for a 2day techinfo account but I cant find a layout of the ECM connector to tell which wire is which going by color is a PIA.

 

Find out what circuits running off that one fuse . Diagram should show each circuit and the wires .Car I was working on gauge fuse fed like n6 different circuits .

 

I have determined it is the power wire for the front O2 sensor is causing the problem but do not see any damage visible. There are 7 different sensors that splice off of this circuit. I have found them all coming out of the splice point but since they are all the same color (and per the wiring diagram) and get power from the same place I need to figure out which of the 7 wires belongs to the front O2 sensor. I feel like if I use a powered test light from the O2 sensor connector the power will flow back through to all 7 wires. Does that make sense? The thing is that it is intermittent and I was able to isolate the wire when it was grounding out, now that I have dug into the splice and wiggled some wires I cant reproduce the problem and don't want to send the vehicle out on the road to leave whoever drives it stranded. Maybe I'm an idiot! Anything I am missing in my troubleshooting?

 

Think volt at sensor only 5volts . Really dont want to power up wires . Can blow computer .If you are sure if its one of those 7 wires comming from slice why not cutting wires from splice untill you find short . If after cutting all wires and still shorts you know you were on the wrong path . I picked up a circuit breaker that replaces fuses so dont have to keep replacing fuses .
Or pick up a short finder . Has circuit breaker you hook up to when removing fuse that blew

 

I wound up cutting them one at a time until I found the right one probably not the best way but I'm sure I found the right one, spliced in new wire and drove an hour to work today it did throw P1135 and the sensor is only about a year old but was a cheap one also getting P0125 which has shown up before. Gonna try replacing thermostat to see if that clears it up.