Hi. I am a new member and this is my second post. I recently bought a 2004 Jeep Grand Cherokee (Loredo I Think) 4.0L, with the check engine light on. The DTC was P0138. After changing what I researched to be the Bank1/Sensor2 O2 sensor, I was able to clear the code, but after a week it's back. Is there anything other than the sensor that could be causing this trouble code?