P1117 an P1121
 

I hate to put up another CEL thread but after reading what my search on the above codes pulled up on this site I decided to err on the side of caution.

CEL came on and I get codes P1117 and P1121, which according to JAAYs thread are:

• P1117 Oxygen Sensor Heating 1 After Catalytic Converter - Below Lower Limit
• P1121 Oxygen Sensor Heating 2 After Catalytic Converter - Below Lower Limit

I am suspicious of the fact that the O2 sensors on both sides post catalytic converter would go bad at the same time.

Any thoughts on what the common factor might be / where I should start to look for a problem.

Car is a base 1998 with 200K miles on it. I am not sure when (if ever) the O2 sensors were previously replaced, though I suspect they were replaced at some time.

Many thanks in advance.

Grab a can of contact cleaner, find each O2 connector, unclip, spray and reconnect at each point. Check the wiring back to the DME in the trunk for any loose or damaged areas, especially around the headers/exhaust.