2tr-fe all coils code, low voltage at coil

I’ve seen similar threads and the recommended diagnostics but haven’t been able to figure out my issue. Admittedly my searching abilities are limited by my lack of expertise.

My truck: 2010, 2tr-fe, manual, 95kmi.

Issue: cranks but doesn’t start. Has fuel to throttle body, relays and fuses look good, battery good. Checked cam and crank sensors and ohms in spec. Showing codes P0351-354; did DM93's diagnostic
(https://www.tacomaworld.com/threads/2nd-gen-information-diagnostics.784008/#post-28042157) with the exception of the J12 connector. What’s weird is the power at pin 1 of the coil mostly shows 0.5v but once did show 12v, then went back to 0.5v after cranking. Truck ran fine when parked a couple days ago (no misfire, rough idle, or stumbling) but hasn’t started since.

Possibly unrelated: I have an electric fan controller that may have shorted out on that last drive home a couple of days ago (mid-wire connector of main power wire is black and bubbled right where it rests near the aft post of battery hold down bracket). Prev owner also had a bypass wire that is connected at pin 4 of EA1 which is ignition on (so fan runs once key is turned), but voltage at that bypass wire (which should be battery voltage) is also showing around 0.5v.

I feel like there is a short someplace, but I don’t know where to look. Any help?

 

So you have no power at the coils or Connector EA1 Pin 4 (Black/Red)?

 

Yes, no power.

 

Check your AM2 fuse (30A) in the underhood fuse box, if it's good then go to the ignition switch and check for power in on Pin 5 (White/Red) and power out on Pin 6 (Black/Red) with the key in the run position.

 

AM2 fuse good, pin 5 (off white/red) showing 12.39v, ignition switch on, pin 6 (blk/red) showing 0 volts.

Harness is unplugged to check for pin 5 and 6, is that ok?

 

No you need it plugged in and then backprobe it with a needle or other suitable tool.

 

Got it, backprobed and pin 6 showing 12.26v. Pin 5 showing similar volts.

 

Still nothing at EA1 Pin 4?

 

Yes, nothing at EA1 pin 4(0.48v).

 

So you need to check it at Connector 1B on the Drivers Side Junction Box Pin 9 (Black/Red) (in) and Pin 10 (Black/Red) (out).

 

Both showing 12v with ignition in on position.

thank you for all the help, by the way

 

So if you have it there and not at EA1 then it has to be broken between there and EA1 or the pin in EA1 is bad, there are no other intermediate connectors.

 

So I pulled the harness at EA1 and tested voltage at 4 pin itself - shows 12v. With harness in and backprobed at pin 4, shows 0.5v. So it’s the harness then, yes? What’s the best way to fix it?

 

So you have power on one side of the connector but not on the other with it plugged in?

 

Correct. I’m not sure if it’s just that wire (since it’s been spliced in) or if it’s the whole harness. Can I safely run t he same check on other pins in that harness?

 

Got any pics of what your talking about where it's spliced and the connector?

What do you mean?

 

Here’s the “splice”:


Regarding testing, i was wondering if I could do the backprobe on another pin in the EA1 harness (and which one) to check if it’s just pin 4 that has wonky connection.

 

It looks like they crimped the green wire to the blk/red wire in pin 4.

 

Eww, I'd get rid of that. It's fine to use an ignition source to turn a relay on to power a load but you really don't want to add anything that draws more than about 3 amps to factory wiring.
What does the inside of the connector look like?

I mean you can but they are gona be different circuits so probably won't tell you much, you could check Pin 7 (Black/Red) it's a different set of wires but it's coming from the same source.

 

it’s pretty clean I think. Just that outside crimp is really crusty. I’ll get to work on removing it. Once power can make its way back thru that pin, will everything work again?