Timing belt replacement instructions

Okay, here’s the update: The click is actually on the firewall in a relay box, not down by the fuel tank.

It is coming from here.

The pic is the ABS relay, so disregard that. I’ve removed the back seat to get at the pump and sender, and disconnected the harness. There is only voltage on one pin, and only 9v I bought a relay for the ECM and swapped with existing, and checked ECM fuse. Manual says if no voltage at pump could be PCM and to take to dealer.

Great to have the diagrams.
I located the circuit open relay. First tried just replacing with a replacement relay, and this did nothing. Confirmed continuity form bottom relay socket to brown wire at pump there are 12v at two of the relay sockets (one parallel to the brown wire socket, one perpendicular). The other socket gets 9v when key is turned (not going off after delay) and during starter crank. The starter fluid did not have any effect. Maybe it didn't get past he throttle body, it's quite a long way. I did already verify spark at the front plug.

No voltage to either brown or white/black, ever.
9V on pink, which is not in the diagram.
I don't understand the blue. Wiring diagram shows brown becoming blue?

I think disregard my prior claim to have tested the relay sockets. Pretty sure it was not the correct relay. The first picture is the panel under the dash. Based on your 3rd image above, I thought the bottom one in the pic was it. However, looking around, that is a standard relay and the pics I've seen of Toyota Open Circuit relay's are different. The second pic for example.

On the other thing you said: "Did you spray starter fluid in the air filter and see if it starts and stalls?" The answer is yes I tried it, and no, nothing happened when I tried that.

Toyota parts department told me the relay is in the engine bay. I'm going to look now to see if I can find it.

I just noticed that a seat heater relay is identified in the third diagram, but this Highlander has no heated seats.
Do you think the pic I uploaded with 3 relays corresponds to your third diagram?
I’m thinking the open circuit relay is quite a bit bigger than the little blue ones.

That seems to be it, as the positions are the same and the seat heat relay is missing.

I was able to pop it out and bring it down where I could get a probe on it.

I’ve got 12v on black and on white, nothing on brown or yellow with key on or starter engaged.

If I’m reading this right, voltage on yellow will cause the relay to connect black to brown.
Can you find out where yellow is coming from?

Yes, fuse has power to both sides, which confirms power to black in the relay.
I used my probe to apply voltage to brown and the pump runs.
So yellow is not getting the grounding signal to close the relay.

Is that a dead end then? New or used ECM?
Or else find a key on 12v wire to splice into and replace yellow with that.

I hear ya. Is the ECM supposed to ground yellow for the relay to work?

What do you suppose triggers something like this? All I can imagine that involved electrical is the battery disconnect before doing the timing belt and reconnect after.