read and reset check engine light

1. If you look at the negative battery cable where it bolts to the body, you will find this is easy to unbolt and a quick way to disconnect the 12V battery. The reason why it is not suggested to remove the positive battery cable is because if you short the positive terminal to ground with your wrench (while the negative side is still connected) you will cause a very big spark which is a safety hazard.

Once the Prius is READY, you can disconnect the 12V battery with no obvious impact to the car's driveability. This is because the DC/DC converter is maintaining the 12V bus at ~13.8VDC. Obviously, once the car is made IG-OFF without the battery connected, then it is not possible to power up again while the battery remains disconnected.

It is not possible to leave the Prius in N with the power off without removing power to the ECU that powers the parking pawl. If you care to do that then you'll need to do homework by studying the relevant wiring diagram.

However, if you raise the entire front end you can rotate the front tires when the car is IG-OFF and in P. One tire will rotate in one direction while the other tire will rotate in the opposite direction.

2. If the check engine light is on, you cannot read the engine ECU DTC without using an OBD-II code reader.

 

There is an easy and safe way to disconnect the battery without tools. Unsnap the red plastic cover (it slides forward once the 3 tabs are released) and disconnect the black cable with the white connector. It is the large one that plugs into the black battery terminal block housing. There is a release tab located under it, and when pressed it will allow the connector to easily unplug:






Once disconnected (and the car is off!), the ECU's will all reset after about 30 seconds, then you can re-connect the plug. The ECM (Engine Control Module) which controls the Engine Light will clear, but the SRS light will not. (this requires a proper scantool)

Note that you must read any powertrain codes before unplugging the battery, otherwise they will be lost.

 

Just a quick not on the Airbag light, my wife has a penchant for storing small articles under both front seats of her 2005. Periodically I will see her airbag light on and (from one of these posts) it is an easy fix where just jiggling the connections under the seat (with the car off) 100% of the time has fixed the light and this has happened 5-10X!!! Seems to be a over-sensitive area electronically, but at least it is simple to fix! Because of the sensitivity, I recommend not putting anything under the seats!

 

My airbag light is on also, i'll try that fix.

Ya that is the easiest way to dc the battery without tools.