Prius Gen Iii Hybrid Display - Strange Fault And The Cure

[Jim255]

So, my Gen III went in for a major service on Saturday. No issues apart from a 12v Battery replacement under warranty. (Incidentally, this can cause the Ready light not to come on at the start of random journeys, leaving you stranded until it decides to change its mind).

On the way home, I flicked the display onto the Hybrid system page (the car side view). I had no arrows going in any direction! Regardless of engine running or not, acceleration or braking - none at all. (The wheels would turn when moving, and the hybrid level changed, so the display was not frozen.)

Car was returned to dealer on Monday. Tried removing the 12v Battery for a few minutes, but this didn't clear the fault. Technician said he had never seen this issue before. Was about to book it in, when the Technician emerged again, and said he would try one more thing. He fiddled about by the Battery, and like magic, the arrows returned.

I asked him what he did to clear the fault. Believe it or not, he unplugged the battery temperature sensor which sits on a bracket above the 12v battery, and plugged it in again. He said one of his colleagues had seen this only once before. Nobody knows how a seemingly unrelated sensor could cause or clear this fault, but that's what he did.

Worth logging it here in case anyone else gets the same issue.

[Grumpy Cabbie]

Sounds like they didn't fully click in the main Orange switch when they'd finished work on your HV Battery. Common issue, mainly with none Toyota dealers.

Not heard about the Battery sensor 'trick' before - ever. Might be genuine or might be a bit of fud to cover not clicking in the safety switch on the Battery.

Anyone else come across this sensor thing before?!?

[Joseph D]

My first thought was that they did not reconnect the plug on the LHS (+ve side) of the Battery correctly. Among other things, this reconnects the re-gen system to the car. Sound feasible?

I have heard of this fault before, but most of the the time the fix is to replace the MFD.

[Jim255]

Grumpy Cabbie, this was a main Toyota dealer. I watched what he did as he did it, so it wasn't a made up story. He didn't go near the hybrid Battery either.

Strange one!

[MEP's Yaris GS]

Believe it or not, he unplugged the battery temperature sensor which sits on a bracket above the 12v battery, and plugged it in again.

To the best of my knowledge that isn't a temp sensor, more a voltage / current sensor, as fitted to most vehicle with start / stop tech now. I could be wrong in this case, but believe its only the traction Battery that has temp sensor(s).

[Jim255]

Believe it or not, he unplugged the battery temperature sensor which sits on a bracket above the 12v battery, and plugged it in again.

To the best of my knowledge that isn't a temp sensor, more a voltage / current sensor, as fitted to most vehicle with start / stop tech now. I could be wrong in this case, but believe its only the traction Battery that has temp sensor(s).

OK - you may be right, but the way it's mounted on a bracket above the Battery is a little strange then!

[MEP's Yaris GS]

Believe it or not, he unplugged the battery temperature sensor which sits on a bracket above the 12v battery, and plugged it in again.

To the best of my knowledge that isn't a temp sensor, more a voltage / current sensor, as fitted to most vehicle with start / stop tech now. I could be wrong in this case, but believe its only the traction Battery that has temp sensor(s).

OK - you may be right, but the way it's mounted on a bracket above the Battery is a little strange then!

Not really, where else would it be mounted? Its mounted in exactly the same place on the Fiat 500 we've got in the house hold with Start Stop, as it is on most Fiat group cars with Start Stop, I assume its just a good location for easy access?