08 Prius inside power outlets not working

Use the Electrical Wiring Diagram (more info) and a multimeter.

For example, does the remote control mirror system (for the side mirrors) work when the car is on? This system uses some of the same power supply and ground connections as the power outlets, so if it works, you could rule out trouble with the ACC relay, the accessory power feed to the driver side junction block, and the ground connection from junction connector J24 to ground point IH.

If the remote control mirror system works, here are some further checks:

• Is the resistance between the shell of each power outlet and body ground (an unpainted part of the chassis) less than 1 Ω?

• With the 15 A PWR OUTLET fuse removed:

• Is the resistance between the two terminals of the fuse less than 1 Ω?

• Is the voltage between the source side of the fuse socket and body ground between 11 and 14 V, when the car is on?

• Is the resistance between the load side of the fuse socket and the center contact of Power Outlet No. 2, the one on the back of the center console box, less than 1 Ω?

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Probe the fuse socket carefully; it’s easy to damage terminals or contacts by jamming meter probes into them.

 

When you say fuse appears to be in good condition, did you test fuse continuity with an ohmmeter or just visually?

 

It’s not odd at all, once you see the Power Outlet wiring diagram, which was kindly shared in a previous thread. (That diagram is for model year 2006, but 2008 is the same.) There are many possible failures that would affect both outlets. Notice how the coil of the relay that switches Power Outlet No. 1 is supplied from the same fuse as Power Outlet No. 2, and the two outlets and the relay all use the same ground connection.

That’s necessary but not sufficient. In other words, if you can see a break in the fusible link, the fuse is definitely blown, but it doesn’t necessarily follow that the fuse is good if you can’t see anything wrong with it. There could be a break that’s too small to see or that’s hidden by the fuse’s plastic case.

Diagnosing this problem yourself would be much easier with a multimeter, so you could check the fuse’s continuity or resistance and make other simple measurements. It doesn’t have to be a fancy meter—the digital multimeters sold at stores such as Home Depot or Harbor Freight Tools for less than $15 would be fine, since the precision and accuracy of the readings isn’t all that important, and you wouldn’t be using it on the hybrid system or other circuits with potentially dangerous voltages.

 

Although it wouldn't normally result in zero voltage, it is possible for the "legs" of a fuse to become corroded enough to affect the circuit. It is like the contacts on small batteries, for instance in a flashlight, where the device will not work until those contacts are cleaned up with a bit of fine sandpaper. In any case, this can be a confusing failure because the fuse will be visibly intact, and when tested with an ohmmeter may still have continuity - either because the spots probed were not corroded or because the probe breaks through the corrosion, but stick the fuse back in and that circuit will still not work. If you have a spare fuse of that rating try putting it in that slot, if the circuit then works, it was the fuse.

 

Exactly that happened to me back in September, stopped my windshield wipers cold. Never noticed any problem at all and then, one day, nothing.

I used an art eraser to polish up the fuse legs rather than sandpaper. Erasers on electrical contacts was a trick I picked up from photographers way back when cameras had film and stuff.

Interestingly, I think I read something recently saying even erasers are now considered too abrasive for the platings on electrical contacts.

 

Probably depends upon what is being cleaned. Gold contacts are no doubt "as thin as can be made and still work" nowadays so those could easily be damaged if there was any abrasive in the eraser. One would hope tin plating would be thicker, as that is a much less expensive material. It seems that car blade fuses are indeed plated, for instance:

https://www.eaton.com/content/dam/eaton/products/electrical-circuit-protection/fuses/bussmann-series-blade-fuses/bus-ele-ds-2009-atc.pdf

Which have:

So perhaps try "sanding" it with a piece of clean white printer paper instead? That should pull off dirt, oil, and grease, without applying very much force to the plating. Otherwise there is always contact cleaner, but perhaps not when the problem happens out on the road (at night, in a rainstorm). This is why there are supposed to be spare fuses in the box.

If the corrosion is in the socket contact cleaner may be the only option, since getting an eraser, or even a small file, into the slot can be impossible.

Edit: when I said "fine sandpaper" a few posts up I was referring to 1500 or 2000 grit. For wood people use 120 or 180 grit for "fine sanding" but that will scratch the heck out of a metal surface.

 

In other words, the 15 AMP Power outlet fuse was burnt. This was affecting the second power outlet with a good fuse since power goes thru a relay powered by the first fuse.

 

What power fuse relay was bad, is there a number on the relay?