Power to fuel pump

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One would think that there are warning lights being displayed on the dash, and generally speaking that also means that there are OBD2 codes (DTCs) being stored in the ECUs. Visit each of the local auto parts stores (even within the same chain) and ask for a free code scan, record the results (the reported DTCs) from each free scan and post them here for additional guidance.

It sounds like you might have DTC P3190 at a minimum, have you gone step by step though the workup?

FYI : you're moderated until you've posted 5 times.

 

Which device/app are you using to retrieve the stored OBD2 codes (DTCs) ?

Here is the step by step work up for DTC P3190 : https://attachments.priuschat.com/attachment-files/2019/10/176519_DTC_P3190_P3191_P3193.pdf

Since the fuel pump works and you have the backseat out, confirm that 12v ends at the fuel pump and to insure that the wiring is intact.

Check if the 15A EFI fuse is known to be good, then testing the relays would be the next step.

 

I assumed you checked the C/OPN relay itself. Do you get 12v at this relay when it is closed or just a pulse as well?

 

I am having this exact issue. 2004 Prius. I thought it was the fuel pump so I ran a battery (12V) directly to the #7 and #3 leads and could hear the pump running. I checked the Amp draw at the pump through the battery and I am seeing 5 Amps. When I check to resistance on the pump (across leads #7, #3) I see 1-Ohm. I checked the Voltage on the leads to the pump while the engine is running and I see 13.6 Volts. I checked the fuel relay up front and it checked in spec as well. I Also checked to be sure it was not the pins by taking the wires (12 awg) from the battery I was using and plugging them directly into the leads for the wires and I still got the Error code P3190. It runs fine when I have external power from a batter powering the fuel pump. I am pretty stumped- any ideas what I can try next?

 

So....
IF the ICE won't run unless you directly "hotwire" the fuel pump (kind of difficult to follow your post), then you need to check the power supply to the pump.

It sounds like you checked the circuit opening relay. I would look at the white connector near the HV battery fan (under the interior panel behind the right rear wheel). There are 3 wires in that connector for the fan, and 1 wire for power to the fuel pump (from the C/O relay).

It's not uncommon to have a body seam leak around the tailgate that drips water onto that connector, and the resulting corrosion can disable the fan or the fuel pump. Usual repair is to splice around the connector and seal the cracks in the body seam.

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If the control module in the glove box was replaced, I'm going to assume that this car has been tampered with in many ways and would be a diagnostic nightmare.

 

UPDATE: After a bunch of testing, hair-pulling, and chasing things down I finally found the issue!

Thank you for the input and suggestions!

My issue ended up being a bad wire between the connector near the emergency brake (driver's kick panel) and the fuel pump.

What made this tricky was that the wire was not completely broken - it would still show 13.6V when the engine was running.
The problem only showed itself when I tried to power a 60W headlight with the wire (simulating the 5A load that the fuel pump put on this circuit) - it would not emit ANY light. I even tried to power a small 12V solenoid with it and it would not switch it on. I then measured the resistance on the wire and found it to be 106K Ohm!

I replaced the wire (cut the old wire out about 3 inches from the connector on both sides) and that got everything working without errors.

I have put about 300 miles on since the fix and all appears to be fixed. I have a more complete write-up if anybody is interested in it - I was not able to post it because it had links and I am too new.

 

Good job! Load testing the circuit is one the best ways to find a high resistance fault.

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Yes, we're interested, and you can copy and paste the images in as well. Just post 2 more times to get out of the "mod box", after 8.5 years.