Here's a little back story. I have a '94 hatch Si with a D16z6 and a 5 speed. When I bought it. It already had some basic bolt on mods and a chipped P28 ecu. It has been my daily driver for a while, but it has a nagging problem that I am finally trying to fix. It pings a lot at low rpms, under 3k. I ran 91 octane for a while, and it was great initially, but after a while, the pinging returned. Maybe the ecu adjusted and the timing is still too advanced. I tried to rest the base timing, jumping the connector, etc. but found that the bulb for the CEL had been removed. Replaced bulb. Hard CEL, Code 1. Checked O2 sensor, found it disconnected. Replaced O2 sensor, hooked it up, still hard CEL. This appears to not allow me to put the ECU in reset mode so that I can reset the timing. I have done a lot of searching, and I am finding that this may not be a simple thing. The chip may only use only open loop (there was no change in how it ran when I hooked up the O2 sensor). Ultimately I would like to figure out everything that I have here and what kind of chip or program I am running, but right now I'd just like to retard the timing a little so it doesn't ping at low rpm and then work from there. I know this is a long writeup, but I figured the more info I include the better you all may be able to steer my in the right direction. Thanks for any help that you can offer.