CEL. O2 sensor
 

CEL code before and same code after all O2 sensors installed(bank 1 sensor 1) any suggestions? Have reset code twice with obd2 device. Car runs excellent, lotsa power, excellent mileage,etc.

1999 Boxster, five spd, 82k , recent IMS upgrade

What codes?

PO 134 code, before and after new o2 sensors installed

This is a great example of why you shouldn't replace anything before you know what the codes are telling you. P0134 is the code for the interruption of the signal from the O2 sensor ahead of the three way cat on bank #1. Usually, this is caused by a problem with either the signal or ground wire connected to the sensor, and is rarely caused by the sensor itself. The diagnostic tree in the factory OBD II manual for the car involves checking the wiring by using a multimeter to test the ohms between pins #1 and 2 (should read 1.8-2.5 ohms at 20 degrees C), and test the ground continuity between each of these pins and the sensor housing itself (each should read infinite ohms). The harness connector pins 3 and 4 should read ~450 mV, and pin 3 to ground should read ~750 mV. Harness connector pins 1 and 2 should show battery voltage. If any of these tests are out of bounds, you have a wiring fault, not a sensor fault.

Thank you so much for the education. And thank you for not being a ‘wise guy’. Your expertise is to be admired ( and much sought after)
Have a good one.

+ 1 on JFP

He has helped many people here including myself, and I had always appreciated his kind support!

JFP and MikeFocke are great resources and never abuse questioners. Class of the forums!

The codes the O2 sensors throw are some of the most specific.

So another question after checking the wiring is what O2 sensors did you replace them with?

Keep the old "bad" ones as spares as they may be good.