Routing of wires for O2 sensor
 

Here's my problem:
- 2000 Boxster, 2.7 L, Tiptronic, ~61K
- just had 60K service done, also replacement of AOS due to failure (classic squeel)

Less than a week after the service was done, CEL comes on. I have a Durametric scanner, so when I got home I check the code - P0140 (Bank 1 post-cat O2 sensor - no signal). I figured this was unrelated to the service. After reading Mike Focke's web page I desided this was something I could tackle myself, so I ordered set of of four replacement sensor (Bosch OEM, $100 each from Amazon.com).

The bank 1 (passenger side) post-cat O2 sensor is an SOB to get at - very little room for leverage. I finally got it out, replaced w/ new, and disconnected the battery for ~30 min to re-set the computer. Next day on the way home from work, the CEL comes back on - same code P0140. I hooked up the scanner again to get the "live" readings from the sensor: voltage = constant at 0.45, resistance = 0. (For comparison, the Bank 2 post-cat sensor reads voltage varies around 0.7, resistance = 0.) If I unplug the sensor I get the same reading. Also tried plugging in the 2nd new post-cat sensor to bank 1 and get the same results. The only fault code that shows up is P0140.

At this point I'm pretty sure the new sensors are OK (and maybe the old one too) but there is a problem with the wiring. I've checked the obvious - plug/receptical look OK, and I've unplug & re-plugged and made sure it "clicked" into place.

Before I bite the bullet and take it back to the shop, any thoughs on what else I can check? I'm wondering if, when the mechanic was replacing the AOS, he may have inadvertently loosened a connection or damaged a wire. Or maybe he unplugged a wiring harness and didn't re-connect it properly. Is any the wiring for the bank 1 post-cat sensor routed near the AOS? Also, anyone know the procedure for checking the continuity from the sensor socket to the ECU?

Thanks,
Frank