Hello there! I'm trying to identify where I can access the fuel pump/sending circuit to connect a relay that triggers only when the gas engine is on. There may be a simple way to do this by accessing a circuit related (like fuel injector circut?) so I'm open to suggestions! Thank you in advance! Kevin
Often, it's possible to get much more promising answers by also including in the post a little bit about what you're wanting to accomplish by doing that.
I'm certainly happy to elaborate. I'm installing a HHO supplementation system that needs to turn on only when the gas engine is running and turn off when the gas engine is off. The HHO system is located in the rear of the vehicle and the control system will be under the steering wheel out of the way. I'm wiring an on/off switch for a pulse-width modular to send power to the HHO system and volt and amp meters on the incoming side of the PWM from the battery, and another on the output side to the HHO cell. I'm using a Volo enhancer chip to modulate O2 and MAP/MAF readings automatically. Thank you!
Hmm, well, the fuel pump circuit is easily found under the rear seat, but perhaps you are wanting to tap in nearer the front where your controls are. There may be a junction up there that would be convenient, I don't know. A job for the wiring diagram! Toyota Service Information and Where To Find It | PriusChat I've always wondered why such systems always write HHO when the rest of the world says H₂O?
I found the circuit on the electrical schematic connected to the ECM labeled "FC" within the ECM Box, with a red wire with an "A" in a circle outside the box and the number 8 next to it on page 110. This circuit is connected to the C/OPN Relay. I think this is the circuit I want to tie into. The two connectors are noted above the ECM box are A57(A) (pg 141 of electrical diagram doc) and D28(B) (pg 142). Both D28 and A57 have more than 8 circuits. It also appears there are multiple versions of this connector connecting into different parts of the vehicle system. I can't upload an image because this is my first post... I have electrical knowledge and can generally read the diagrams, but there's no legend to understand the labeling. Anyone help enlighten me? Appreciate your responses!
Or a second thought is to tie into the output of the C/OPN circuit signal to the sender if it's in a convenient spot.
Yeah that's the circuit opening relay I think anywhere in that path might be okay that basically keys up at the start of turning the car on I'm not mistaken chap will tell you in a minute
The legend for wire harness connectors is right there on the drawing. Like where the ECM's "FC" output is labeled "A" pin 8, and right up above the ECM there you see that "A" refers to connector A57. You can find in the connector diagram exactly what connector A57 looks like and which position is pin 8. Connectors on fuse/junction boxes are a little different. Where you see the other end of that wire at 1B pin 7, you look in the relay/fuse locations section for the diagram of that box and what connector 1B looks like. A thing like AR1 that you see lower down is a connector joining one wire harness to another. Those also have their own section. If you are signed in to TIS using the actual wiring diagram online, you can just click any of those things and the whole circuit gets highlighted and you can click and jump around between all the connected diagrams and details. Of course if you are just looking in a paper book or PDF, following the cross-references is up to you. For extra fun, sometimes you're using a PDF somebody put together with a bunch of Print-to-File clicks in TIS and it's missing some of the sections they never bothered to print.
OK, I figured it out for anyone interested: I have two options: 1. The EFI Main fuse in the engine compartment is connected to connector 1B. In 1B the fuel sending circuit is Pin 8, which is where you can tap the circuit for the relay to trigger the hydrogen fuel cell to turn on. This would mean I have to disconnect the connector underneath the fuse box in the engine compartment. OR 2. The interior junction AR1 at circuit 8 (Red) which is the circuit that switches on the fuel sending unit. This is at the drivers side on the left side where the group of connectors/junctions are hidden behind the panel to the left of the E-Brake. Thanks everyone and especially ChapmanF for your help! The TIS system worked great!
