Brake/!/ABS/VSC continuing problem...

When the lights come back on read the codes. Now you have got rid of the low 12 volt problem there should be no false codes and the real fault can be traced.
If you have a volt meter check the battery voltages at the rear of the car under the same conditions. It is not unknown for the MFD to under read the voltage by as much as 0.5 volts.
At that millage the car is just run in, my own car is at 99,920 so not far behind you, but mines a 2008.

John (Britprius)

 

I would definitely check the voltage with a volt meter as John (Britprius) stated above.

I would also consider the possibility of a "defective" battery. Just because it is new doesn't mean it is perfect AND fully charged. I would also check the voltage when the Prius is in "Ready Mode" to confirm the charging system is working properly. Should read 13.8 to 14.2 volts on the MFD in "Ready Mode".

If the voltage is good in all of the test's I would then consider any after market devices that might have been added at some point. I am referring to alarm systems, remote starters, amplifiers, stereos etc. Any of those devices might be causing a excessive drain if there is a problem with that device. It is not uncommon for problems to crop up over time with aftermarket devices added to any vehicle.

You can also check the quiescent draw with a volt meter connected in series providing the meter has a amp measurement on it. The draw should be a few hundredths of an amp when the Prius is in "Ignition Off Mode". (Powered Down). Few Hundredths equals .0X example .05 amps. IIRC the normal draw is around .02 amps which is not a lot of current flowing. If you find a excessive amount of amperage flowing, that will indicate that something is not turned off when the Prius is powered down. This could be due to a defect in a aftermarket part or a relay sticking somewhere.

You also mentioned a "splice". I would check the resistance of the splice with a ohm meter. There should be no resistance on the splice. If there is a lot of resistance, that would explain a lot of things.

I also agree that your car is far from ready for the scrap pile. Our 09 has 78K on it and I plan to put at least that much more on it. You got a lot of life left in yours. Just need to work through this little glitch... It is cheaper to repair than start making payments again.

 

The quiescent current draw on 2G Prius should be around 0.02A (20 milliamps).

 

Thanks for clarifying and correcting me Patrick. I edited my post above with the correct information.

Ron

 

U0100 and U0293 are valid DTC. U0293 is logged by the engine ECU and reports that it lost communication with the hybrid vehicle ECU. U0100 is logged by the hybrid vehicle ECU and reports it lost communication with the engine ECU.

However I am not convinced those DTC are valid since they were not previously reported by your dealer. These DTC point to a fault either with the engine ECU, the hybrid vehicle ECU, or the associated wiring harness. Both ECUs are hiding behind the glovebox. Do you know of any accident damage or other trauma that would affect that area?

I suggest that you should measure the voltage on your 12V battery after the battery has rested overnight, to get rid of the "surface charge" that inflates the voltage reading. If you find that the open circuit voltage is below 12.5V, first fully-charge the battery, then clear the DTC, and see if the warning lights come back.

If they reappear, then you'll need a better code reader such as the mini VCI previously recommended, or else visit your dealer again.

 

If the BRAKE, ((!)), ABS, and VSC lights are still on, that means that the skid control ECU has logged a DTC. You'll need to obtain the code(s) to provide a clue about what to do next.

 

Is this from today? or yesterday?

 

Yes, so what is required is to have a Toyota dealer retrieve the current DTC again; or else you need to invest in the proper diagnostic tools so you can DIY.

The three codes that you obtained from the earlier dealer visit all are associated with the transmission control ECU. That ECU has nothing to do with the warning lights that you say are lit. It is likely that those codes were produced by the weak 12V battery.

The skid control ECU is producing the BRAKE, ((!)), ABS and VSC warning lights; hence there must be current DTC associated with that ECU.

 

Actually, DTC C1243 means that the yaw rate (deceleration) sensor is not working. That is a plausible code based upon the skid control ECU-related warning lights that had been on.

DTC U0121 means that the power steering ECU has lost communication with the skid control ECU.

DTC B1421 is an air conditioning fault code which just means that the sensor is in the shade. You can find the sensor along the edge of the dashboard near the bottom of the windshield. That helps the auto air conditioner function decide how to set the fan speed. This code can be ignored.

I think you are going to need professional help to make progress on this, assuming C1243 and U0121 are valid and return. These DTC are not commonly seen.