89 560SL Check Engine Light HELP!

[xke190sl]

The check engine light has returned on my 89 560SL (74,000 miles). I have read all the posts and have tried the following. The light stayed off for 2 days and now has returned.

1. O2 sensor replaced with an original Bosch.
2. EGR valve cleaned.
3. New battery.
4. Checked all vacuum lines
5. Disconnected the battery for 2 hours.

The car sounds/runs perfectly smooth. Idle is perfect at startup and hot.
I made/tried the diagnostic tool mentioned on the list. This is a NC car and I get no power when plugging into the dignostic port (port 1 and 3) on the left fender well in the engine compartment. I do get power with port 1 and 6 to check the SRS. My 88 560SL is the same.

Anyone other things to check? How will my mechanic retrieve the code? I am almost ready to take out the bulb!

Thanks!

Richard