96 LSS throwing codes.....

I have a 96' LSS throwing P1133 and P1406.
I have changed the O2 sensors about 5 months ago.

Can something be causing these codes to appear?

Yes something is causing these codes, have done a google or site search for the definitions?

Yes something is causing these codes, have done a google or site search for the definitions?
Yes , it appears they are electrical codes for bank 1 O2 sensor and pintle position sensor for EGR.

The O2 sensor code can be, under the right conditions, be caused by a bad EGR....

The only way to know for sure, is with a scan tool.....

The scan tool is needed to check O2 sensor activity, especially on startup to see if the heater circuit is helping it to start quicker......and if there are sufficient cross counts.....

Also need to check the EGR pintle position with scan tool to see if it is stuck open or if there is a discrepancy in position between commanded position and actual position....