Check engine light on 2015 Prius

You might want to invest in the Scan Gauge 2,

I can really depend on my Scan Gauge 2 to continuously monitor the status of the systems in my Prius v.

I configured mine to monitor the 12 volt condition, the water temperature of the engine coolant, the temperature of the inverter and the traction battery temperature all at once.

Noticing that there is a rise in the ICE's coolant temperature would have alerted you even if the check engine light was not triggered.

Alternatively, there are many other different parameters that you can also monitor, if that is more important to you.

If there is an OBDII fault code or CEL , I can access it readily by pushing a few buttons, a function I fortunately have not had to need to use.

The photo shows the display that I monitor with the Scan Gauge 2 mounted on the top of the steering column.

Whenever my dealer worked on my car, all they dis was to unplug the Scan Gauge from the OBDII port, did their work and re-plugged the Scan-Gauge back in. It works automatically all the time when the car is turned on, especially when the ICE is not running.

There are no apps to open. Pushing one button switches to reading a fault code.

 

Sadly I had to give up on my SG: not sure but apparently having it constantly weighing on the OBD port was the cause of increasingly frequent Check Hybrid Warnings and brakes reverting to default behaviour.

 

No such problem. I tied the extra cable to a point under the dash. There is no extra weight on the OBDII connector.

 

Most likely it was a CAN bus problem. Others have reported similar issues with SG2. Some suggest not connecting the cable when the vehicle is on even though the instructions seem to suggest the opposite. Others blame SG2 firmware revisions.