Chrysler Repair: 97 LHS error codes P0135 & P0155 when restarted hot, egr tube, p0171 system too lean bank 1

Question
Hi Roland, I've learned a lot from your answers to the questions submitted by others.  This is my first.  I have a '97 LHS with 152,000 miles.  I replaced both forward O2 sensors after getting P0154 - O2 Sensor CKT No Activity (Bank 2 Sensor 1).  I also got P0171 - System Too Lean (Bank 1).  Based on your answers to other's questions, before I replaced the O2 sensors I checked every vacuum hose and repaired  several leaks.  The EGR tube was loose where it attached to the EGR valve, which was causing a major leak.  I used my scan tool to clear the codes after each repair I made, but the codes kept coming back.  I also inspected and cleaned every electrical connection I could find with contact cleaner, and removed the air intake plenum and cleaned it, replaced all gaskets and synchronized the throttle bodies which were off by a very small fraction.  The P0171 and P0154 codes went away. But now, I can start and drive the car and get no error codes if I let it cool completely before restarting it.  If I restart it while the engine is still pretty warm or hot, I get two 21 trouble codes using the ignition key method and and P0135 & 155 with the scan tool.
Can you give me any suggestions as to what to check next?
I appreciate any help you can give me.  
Del

Answer
Hi Del,
Those codes are for the right side oxygen sensor (heater failure, sensor shorted to ground). I would check for continuity between the gray and white wire of the sensor as those are the heater wires. The signal wire is black on the sensor side of the disconnect and tan/white on the pcm side. I would check to be sure that wire is patent to pin 49 of the pcm and not grounded. And be sure there is 12v between the gray and white wires when the ignition is in the "on" position. You may have some burned through wires. Just in case, check the left side too, as I could have these reversed. The signal wire on that side is  black/dark green and goes to pin 41.
Roland