2000 Mitsubishi Diamante..Failed Inspection due to..

[quote:e90165a1b8="tzeitlinger"]I recently failed inspection due to OBD codes PO431, PO141 and PO1751. I was wondering how expensive these repairs would be? I drive a 2000 Mitsubishi Diamante/Automatic/6 cylinder/125000 miles. I also noticed the check engine soon light will not go off. Can my local mechanic turn off that light or does it have to be done by the dealer?[/quote:e90165a1b8]

P0431 Warm Up Catalyst Efficiency Below Threshold (Bank 2)

P0141 Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

P1751 Shift Solenoid #1 (SS1
As you see your codes translate to problem area
In this case you should start by changing O2 sensor
As for your mechanic he should have the ability to take care of your problem
Ask him

Good luck
Let us know