2000 Taco cranks but won't start with AC&AC Fan turned on....

Interesting, that leads me to believe the problem is in the J9/J10 junction connector under the underhood fuse box. Srry I can't find a better picture of it's location.

First I was thinking Ground Point EA but since the lights work that leads me to the junction connector.

 

Found a connector view for it.

 

So i was on to something.....

 

So are you thinking the plugs might be loose or have a bad connection there?

 

Possibly.

I think we should see if the LEFT FRONT turn signal works with the blower on.
And see if it works with to blower off.

dm93 said check the right, but the diagram above says its the LEFT?

 

That's what the data is telling me based on the tests.

We know the truck won't start with the HEATER Relay unplugged or with it plugged in and the blower turned on.
Well when the HEATER Relay is off Pin 2 is connected to Pin 4, Pin 2 goes to the Blower Motor which has a path to ground via the Blower Resistor. Pin 4 of the HEATER Relay goes though the J10 connector to Ground Point EA.
The EFI Relay also get's it's ground through the J10 connector from Ground Point EA, therefore my theory is there is an open in the J10 connector and the EFI Relay is grounding through the HEATER Relay, Blower Motor, and Blower Resistor to Ground Point IE when the relay is off instead of grounding through J9 to Ground point EA. But If Ground Point EA was bad the parking lights and turn signals in the front wouldn't be working I wouldn't think.

Certainly wouldn't hurt to check Ground Point EA though before digging that connector up.

 

So all signals work with blower motor on or off --- here is something I just noticed though, with the key in position 2 engine off -- the check engine light is on --- when I switch the blower motor on, the check engine light turns off --- when I switch the blower motor off the check engine light comes back on...

 

Well, I had a suspicion early on.

 

Did you go out and visually check that the front bulbs are lighting?

That confirms to me the EFI Relay is losing it's ground when the blower is on which tells me it's grounding through the HEATER Relay instead of where it's supposed to which would be EA

 

Yes I visually checked every light to make sure it was working correctly. So from what you both have been educating me on, I have an issue in one of the plugs, somehow, that occurred someway. I'm curious of why the truck will idle fine and rev up fine while parked with the AC and blower on, but when I'm driving it will die, not right away, but at some point dies (cuts out).

 

That's a good question, my hunch would be that the circuit isn't completely open but has a significant voltage drop (green crusties would be my guess). Standard automotive style relays need around 5-7v to turn on but can be held on with as little as 2v.

Of course I could be way off here but I'm going by symptoms and wiring diagrams and it point's to a bad connection in the J9/J10 connector. You could check the EFI Relay ground if you have a meter and a small piece of wire, stick the wire in alongside Pin 2 of the EFI relay and put 1 meter (set to volts DC) lead on the wire and the other to battery negative when the truck wont run. If it reads anything more than about 0.2v you definitely have a ground problem to that relay.

 

Thank you, I will check it out. I do have a meter to do that with. I will also clean contact points within the sockets with Electronic spray, unless one of you think that's not a good idea.

 

now this is tacoma world as it should be.

 

Certainly check the voltage drop on that relay ground before you get too involved and make sure we are on the right track but if it's bad I suspect your problem will be quite apparent when you find it as a relay only needs around 200mA of current to turn on.

 

Okay, I checked the #2 pin on the EFI relay both with the blower switch on and off. When switch is off I get .0001volts with switch on I get 9.5volts. So obviously there is voltage coming through where it's not supposed to be. Now the question is why and what to do to fix it.

BTW I really appreciate all the help I've received so far with this. I am so glad I joined this group.

 

Check that ground point at EA just to be sure it's good but otherwise your gona have to find the J9/J10 connector as I bet your problem is there.

Never should have 9.5v on a ground.

 

Really good thread.

Really glad I don’t have same problem.

 

I will do that, if you don't mind clarifying "EA" for me please. Also, just a bit of info here. I understand about relays in part because I used to do car stereo and alarm systems way back (way, way back), anyway, I decided to make a harness that allows me to connect the 3, 5 and 1 pin to the relay outside of the fuse box and connected the ground directly to the battery. The truck starts with no problem with the AC and blower switched on. Obviously, I don't want to leave it this way, but the problem is close now thanks to all of you here. I at least know for sure that the problem is at the #2 pin on the EFI and it's getting voltage when it should just be ground, minimum mV.

 

See the picture I posted, it's on the left fender.

Ah ok, well I try to explain things like I'm talking to someone with limited knowledge in basic electrical because most people don't understand relays and voltage drop.

That's a nice workaround until you can pinpoint the issue.

 

You have been more helpful than I can express. You gave me a direction to go that I would have never thought to head. It's only because of you and TriShooter that I was able to get to the work around that will at least by me some time until I can figure out what is the actual thing causing the problem. I know I would have never thought of the EFI relay getting power on ground side without both of you helping me.