Buick 3.8 codes

Got a p0140 code. Rear O2 sensor no activity. Changed sensor 1 yr ago. Not Bosch or delco sensor. So, code is back. I did quick code check and also see a 1404 code for egr pintle range.a stuck egr usually makes car run poor, sometimes stall. But motor purrs like kitten. No driving issues at all. I clear code and 15 min later both come back. Any connection between both codes or total coincidence?

If egr ports are carboned up, the motor will run the same even if egr is stuck open. Since the egr will have no affect. But computer will set code cuz egr is open or stuck.

If the port is carboned up, the EGR flow may be minimized and the engine runs good, but the valve doesn’t completely close, hence the pintle range code. If you are getting that much carbon on the EGR valve, then you are also getting it on the O2 sensors, but for a rear O2 sensor, first check the connector for moisture or water build up. Some of these connectors are in a bad location and get very wet.

We were getting 0140 for awhile. It would come and go. Changed sensor last yr. code stayed off for awhile and came back. Than last week p0102 popped up. Maf low voltage. Changed maf and got the 1404 code within 24hrs. Huh? So, the 0102 and 1404 both came about the same time and recently while we have had 0102 forever