Question

I got the engine code P0138 and P2271 on my 2005 Cadillac SRX, and engine light is ON

Answer 1

Since both codes are for the Rear O2 sensor Bank 1, you probably have to replace the Rear Heated Oxygen Sensor Bank 1 to fix the problem.

P0138 CADILLAC - HO2S Circuit High Voltage Bank 1 Sensor 2
Read more: https://www.autocodes.com/p0138_cadillac.html

P2271 CADILLAC - HO2S Signal Stuck Rich Bank 1 Sensor 2
Read more: https://www.autocodes.com/p2271_cadillac.html