On the last couple of journeys there has been intermittent loss of power / acceleration that seems to be the ICE cutting in / out (under acceleration). Skid light comes on as the ICE cuts out. Fault seems to disappear after 5 min or so driving. 12v battery is under par, but I believe shouldn't cause this problem. Any suggestions before I take it to a dealer for a Code check? PS I have just put the 50mph spare tyre on the front, but that shouldn't cause this problem either! (24k miles on clock).
12 volt can be the cause of just about any problem. think of trying to power your computer a few volts under the minimum.
Because that spare tire isn't the same size, it spins at a slightly different rate that the others, and can trick the VSC into thinking that something is slipping. Get the primary tire fixed or replaced, and get that spare back into the trunk. Or, at least get that spare off the front, shifting it to the rear.
Did you inflate that tire to 60 psi? If the tire is underinflated, that means that wheel will spin faster than the other tires which will cause the skid control ECU considerable heartburn and shut down drivetrain power.
I have read that the 12v battery's job is done when the ready light comes on - the DC/DC converter / traction battery takes over, and the 12v could (in theory) be disconnected. So less likely to be the battery causing this problem?
The small spare is for emergency use only, to allow you to get to a safe place for replacement. It is not intended as a substitute... with any type of vehicle, Prius included. The vehicle will not perform as well with a mismatch like that. So, it should be no surprise warnings are being triggered.
I've replaced front tyres. Return journey ok. On the way to garage, the symptoms were (for first 5 mins) constant skid warning. Almost no acceleration. ICE cutting in / out. Symptoms stopped when the traction battery was getting low, at which point the ECU seemed to say ' if we don't get this ICE started now, the traction battery will go flat', and from that point the car behaved normally (no skid light / normal acceleration). Similar to when the engine cuts in at the end of EV mode. Fingers crossed problem solved.
Your spare is exactly the problem. It is of a slightly different diameter than standard tire and causes traction computer to cut the acceleration. Also, I would never put doughnut spare on front - I would spend extra time but switch with rear. Alex
Maybe 2nd gen with its touchy traction control is making things worse, too. I drove maybe 10 km on temp spare with our 3rd gen with nothing untowards. Maybe helped it was on rear too, but still the same diameter differentials at play, I would think.
A few years ago my wife was driving the 2004 and she hit debris on the road which caused the right front tire to blow. I was riding along and installed the compact spare at that position. There was no problem driving at speeds of up to 60 mph. We bought a pair of tires to replace the failed tire plus another tire with the lowest tread depth, the following day.
And thanks also for coming back with the confirmed solution. That helps tune the forum's advice for future questions.