2004 gen II Code U0100

That indeed is a rare problem, thanks for sharing your experience.

 

shit i have the same code u0100 along with u0111, putting gas made it go away but its coming back now (and i KNOW I HAVE TONS OF GAS IN THE TANK).... how much did you get billed for? and since i cleared the codes how can i replicate the problem so the dealer can fix it?

EDIT: I 'm guessing cleaning the MAF sensor won't solve my problem :S

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Phil, if your car has the same problem as the OP, there is a large relay assembly in the main relay/fuse box next to the inverter that needs to be replaced. That will probably cost you around $500 since it is not easy to remove and replace that assembly (which contains four separate relays.)

As far as replicating the problem, you need to drive the car until the warning lights reappear, or else tell the service writer what codes you retrieved. The problem with the latter approach is that if the problem doesn't happen right away for the service tech, he will indicate no-trouble-found and you will get billed for an hour of labor time without any corrective action being taken.

 

many thanks for the fast reply patrick! you've been always the man of the hour on these forums!

I only drove 1 km from the gas station to my work place without it hic uping... but if I drive until a problem actually happens then my car would be stuck on the road needing to be towed to toyota.... so I'm not sure what the best course of action is?

its amazing that i have found only one thread related to codes U0100 and U0111 so it is a rare problem indeed

 

i'm about to go home... hopefully I won't get stranded on the highway again :S i will stop by the gas station to see how many liters it can fit in, in case some gas that managed to leak out (although I don't see how that is possible to be honest but hey it fixed my problem last time!)


seems the codes are related to the high voltage battery? or this relay that the OP speak of

U0111 Lost Communication With Battery Energy Control Module "A"
U0100
Lost Communication With ECM/PCM "A"

 

so i went to the gas station and put gas in it , thinking it was dry and after 7-8 liters OVERFLOWWWWW

ugh i think i made things worse by damaging the bladder... so i did my best on my 14 km run to drain as much gas as it can before it expands the next day when the sun comes up.

my mileage was 8.0 liter/100 km for my 14 km run, for the first time ever wasting gas in a prius was INCREDIBLY DIFFICULT :S

but the code did not come back... but now im more scared than ever to drive it ... sheesh.. will keep this thread updated

 

I don't have access to the Prius repair manual this week. However if you are concerned about driving the car, perhaps you should visit your local dealer, let the service writer know the DTC that you retrieved, and suggest that the integration relay within the main relay/fuse box should be replaced - if you are ready to bet ~$500 that the problem is caused by that.

 

i wanted t update this thread regarding the integration relay fuses with my car since my service advisor called me this morning ..


she asked me if it was the relay which snaps on and another that is under the box? i asked her what are the costs for each part and she quoted me around 200$ for each... labor is around 1.5 hours to install both so when it comes down to it, it works out to around $500 bucks... which is close to what the OP quoted...

of course its been 200 km since my incident and nothing has happened yet... so im on the fence where as to gamble fixing it or not but will keep this thread updated if it happens again

 

interesting ^ thanks ohroadwarrior, maybe i should cheap out and purchase salvage parts.... so i would assume its not that hard to install although working 1.5 hours on the side of the road would present a hard challenge! thanks for the info

 

It would make much more sense to replace the relays at a time and place of your choice, rather than wait for a failure and try to repair the car while parked on the side of the road.

 

I had a u0100 error on the road yesterday, no ICE, but car still drove on the battery (luckily I was at an exit and got to a safe place within seconds). Additional symptom, my gas guage was flashing empty then flashing full. I knew gas wasn't the problem but topped up just in case. Techstream could not communicate with the engine ECM to get codes but it did pull the u0100/211 code from the hybrid system. In my case a blown EFI fuse in the engine compartment box appeared to be the only issue, although now I'm wondering if there is a corrosion issue under that relay box that caused the fuse to blow. I drove home 180 miles after putting in a new fuse without any noticeable issues.
Edit: 2006 with 148000 miles.

 

2008 gen II with 170000miles

I just received the christmas tree warning lights in my office parking lot. 20 mile commute with no problem. Powered off to drop off a package, then powered up and pressed the eV mode button...after moving the vehicle 200 feet in eV mode (I've added this feature) the vehicle died as I selected Reverse. I had been hardly moving through the parking lot and was just preparing to back into a spot when this happened...I can't recall if it was at the same moment I had selected Reverse...but it was close. After power cycling the vehicle a few times (engine kicked in, warning lights still on) I backed into the slot and retrieved the DTC codes. Note: The previous day I'd added an OBDLink LX to the vehicle and have been running the Torque app on an Android phone providing diagnostic information. The DTC codes I retrieved were: P0A1D, U0100, U0111 and U0293. I proceeded to clear the codes with the app and power cycled the vehicle again (no warning lights this time), and put it into reverse and waited for the engine to kick in (still no warning lights).

Is it possible that the bluetooth dongle or eV Mode operation could be messing with the ECU? Should I unplug the dongle after every trip (I normally have it in "read only" except when I cleared the codes).

Any other users experience this anomoly? The drive home will have some pucker factor, as I deeply dislike being stranded on the freeway.

Update:
I had no problems driving home. HOWEVER, on the way in to work I stopped for an errand...still had the OBDLink LX installed and was monitoring the system with the Torque app. I'd left the app running on the phone...but shut down the car for about 15min. Then in the process of driving the last mile to work I noticed that the Torque App appeared to not be communicating with the OBDII device (or wasn't communicating with the ECU since it was not showing any RPM. So I shut down the Android since I was just a few blocks from work, no big deal, right?. 15 seconds after the phone shut down, the ICE died while cruising along at 50mph and I think ALL the lights came on (check engine, big read exclamation triangle of death, etc)...including all the instrument panel indicators (D,N,R,B,etc). So I coasted to a stop...proceeded to turn off the car, (I tried multiple ON/OFF cycles with no improvement on indicators even without the OBDII dongle)...so I plugged the dongle back in, restarted my Android and logged into the ECU to clear the DTC codes (I turned on the car w/o stepping on the brake pedal for this). I then restarted the car...and drove off with no problems. I am hoping this exercise in cool diagnostic toys while operating the car doesn't actually BREAK something expensive. To be continued...

 

See I scanned my Prius to death /!\ | PriusChat

 

U0100 on my Prius was caused by a blown fuse. Filling with gas / unplugging the 12v battery did nothing. Had to leave car and walk home until morning when stores were open. My $20 oxygen sensor shorted and blew the top right, blue, 15 amp fuse. Any auto parts store and maybe Walmart will have a box of 15A Low Profile Mini Fuses for $5.

Fuse box is top right of engine compartment under a black plastic top. Use pliers and maybe fingernails to pull out the colored fuses (yellow, red, blue, green). Hold the fuse flat, and look at the metal inside. If the metal makes a complete U shape, it's good. If the metal is two distinct pieces, it's bad. Once replacing, my car started and I went to the Toyota dealership to drop $180 on a legitimate oxygen sensor.

ps. I unhooked my bad O2 sensor before replacing fuse. Also, different component failures may cause your U0100, so first check all your mini fuses.

 

Thank you for a post of sanity. Yes, U codes are communication errors between different ECUs in the car, and they are rare problems, and when they do happen there are as many possible causes as there can be reasons for one computer to fail to talk to another. One of the computers being offline because of a blown fuse is certainly one of the things that could cause it, and then there could be various possible reasons for why the fuse blew.

So when U codes come up, often you just have to plug away at possible causes until you find what the cause is in your car and your situation. Anybody else's post about what it turned out to be for them might be useful if, by coincidence, it happens to be the same thing for you.

When plugging away to find what caused a U code, it is helpful to start with two pieces of information: (1) the exact U code, and (2) which ECU in the car reported it. Then you know both parties to the communication problem, because the ECU reporting the code is the one saying "hey, I can't talk with so-and-so", and the specific U code tells you which ECU so-and-so is.

The "multiplex communication system" and/or "CAN communication system" section in the repair manual has diagrams of which ECUs are connected to which and by which networks and the way those are laid out, so when you know which two things aren't talking, you can zoom right in on what the possible causes could be.

Some scan tools don't show you which ECUs reported the codes being shown. For U codes especially, it's more helpful to use a scan tool that does show that.

 

My issue was a blown 15 EFI fuse.
Might want to check that first.

The culprit that caused it to blow was exposed 02 sensor wires that were rubbing against the body.

 

When there are so many possible culprits, if everybody posted about what turned out to be the culprit in their car, sometimes the result'd be just a jumble of things to check "first" for the next person to sort through, when they could just be following the tree of elimination steps in the repair manual. For this code, an early step is to check the +B voltage at the ECM anyway, so a problem with the EFI fuse would be caught in short order.

That said, it isn't hard to check that fuse first if you want to.

And a very common complication of catalytic converter theft is having those O₂ sensor wires left dangling under the car where they can short and blow that fuse. So certainly if there's been a converter theft in the car's history, those wires will be an early place to look.