My 2006 2nd gen Prius has suddenly thrown the red warning triangle and on investigation with a code reader it shows P0420, P0505 and one it can't read. I've erased the codes and it runs ok for a short while but re-throws out the same codes, though sometimes it also shows VSC and the car with !. A friend also noticed that the battery cooling fan is running a lot. TBH I have not noticed whether it is running more than usual. The hybrid battery also rapidly discharges when the codes appear. Help. What is going on???
I forgot to mention that I've booked the car in with my local Toyota dealer next week for a diagnostic check
Welcome to Prius Chat . Some questions: What code reader are you using for the codes? How long have you had the codes be displayed? Have you checked the cleanliness of the hv battery fan? The P0420 points to the cat converter. Does your Prius consume oil? Keep us posted .
The P0505 code is telling you that there's a problem with the Idle Air Control System. It may have corrected itself, then again, it may come back. I'd clean the throttle body and the IAC valve and see what happens.
Some cars have an Idle Air Control valve, which illustrates the risks of looking codes up in broad searches instead of in the Repair Manual. In the RM there are about three pages on troubleshooting P0505, which involves the Electronic Throttle Control System on a Prius (one throttle motor does all the control whether at idle or under load, there is no separate IAC). The code is set if the engine's idle speed ends up 200 rpm or more different from where the ECM is trying to control it, five times or more during a drive. The workup pages do say to investigate any other codes you may have before digging into this one, as the others may be the reason for the out-of-spec rpm. So, those would be the catalytic converter code, and the code-that-couldn't-be-read. I would try to get access to Techstream, or another Prius-aware reader, in order to get the mystery code(s). -Chap
Here are the trouble shooting guides for both P0505 and P0420.. DTC P0505 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Prius%20Service%20Manuals%202004/%E4%BF%AE%E7%90%86%E6%89%8B%E5%86%8C/04pruisr/05/2054m/cip0505.pdf DTC P0420 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Prius%20Service%20Manuals%202004/%E4%BF%AE%E7%90%86%E6%89%8B%E5%86%8C/04pruisr/05/2054m/cip0420.pdf
