P3190 Code - Failed Fuel Pump (Resolved)

I posted about this in another thread, but I was just sort of piggybacking on the OP's thread, and in any event, he posted about replacing his fuel pump preventatively, not bc he had any issue with it.

I decided to create my own post to help others in the future.

My car stalled, then started but idled very low/slowly, would stall again, repeat. It threw all sorts of lights on the dash: "Check Hybrid Status", the triangle with the exclamation mark, and the CEL light, which my scanner showed was P3190.

Bc it's a 2010 and I'd meant to - but never got around to replacing the 12V battery preventatively - I thought perhaps a low/bad battery would cause these issues. Bought an Optimum, popped it in and...worked. Sort of. The car started up fine, I test-drove it for a few minutes, and figured I'd solved the issue.

Not so fast. The next day, the car experienced the exact same problems, but this time, the car wouldn't even start, or go into any other gear but Neutral. Resigned, I had it towed to a Toyota dealer, who called an hour after it arrived saying it was a bad fuel pump, and it'd be roughly $1,000 - $600 for the fuel pump assy, and the rest in shop and labor.

I decided to attempt a DIY fix first, so I had it towed back home. Putting faith in their diagnosis, I bought a used fuel pump assembly from ebay for under $100, from a 2014 donor Prius.

On disassembly: the locking ring that locks the assembly into place supposedly needs a special tool - a glorified spanner wrench essentially - that Toyota doesn't apparently sell, if they ever did, but there are lots of options online. I tried one from Amazon (Great Neck 25156) but it didn't work bc the adjustable arms that fit into the slots of the locking rings were too thick. In the end, I just used a screwdrive and hammer and pounded it with lots of small hits to get it off, without issue really. On reassembly, I put a bit of lubricant on the locking ring tabs to reduce friction.

With the bad fuel pump out, I did a quick resistance test per the method in the service manual, and the pump measured within spec. It measured 1.5 ohms, with the spec range being 0.3-3.0 ohms. So here's a question: what else about the pump - besides resistance - can be measured? I assume the dealership diagnosed this issue with Techstream. What in Techstream would have found this issue? Also, I'm looking into getting a better OBD scanner, as the one I have is basic and won't read sub-codes. Suggestions?

I'm happy to report that, with the new (used) fuel pump in, all is fine, so the dealership was right and it was definitely a failed fuel pump.

 

Yes, good point. I hadn't considered the mechanical portion. I guess my assumption is that the electrical portion would be far more likely to fail than the mechanical one.

I'm guessing both you and Pluggo are spot on: something mechanical gave up the ghost, resulting in low or inconsistent fuel pressure. My testing the pump's resistance was only half the story.

I was just poking around and googling about fuel pump operation, and came across this rather good illustration. It's not the Prius's pump, but rather a generic fuel pump, but likely most are just like this, including the Prius's. So who knows what went wrong mechanically, but perhaps a spring malfunctioned, or the diaphram, or one of the other myriad mechanical parts. Who knows. Next time, and for anyone else having this issue, measuring the fuel pressure is the *other* half of the troubleshooting method.

Here's a link to the service manual for testing the fuel pressure: https://attachments.priuschat.com/attachment-files/2018/09/152972_2010_Toyota_Prius_Repair_Manual_-_Fuel_Pressure_check.pdf