I just thought of something... did you take the resistor out of the old PMD and put it into the new one when you switched them out? It's an insert that fits into the plug part of the PMD. The thing SHOULD relearn on its own, but...
I think it's a 99 ... the OBDII should relearn, but I've seen the need to do that on more than one occasion. If the new PMD has no resistor at all, it can cause issues
Yeah. Lol. I'm pretty sure obd2 will run with the wrong one, I'm just not so sure it will run without one... the Doc would know, but he's smarter than me