'96 XP wiring diagram - AND general MPEM electric question(s)

[Ckrawiec]

OK, I don't own a '96 XP but am helping someone out with one....I see some "strange" items on the wiring diagram, so questions:

1) What is this "Battery1, Battery 2" - Pins 2-19 & 2-20 in the MPEM?
2) What is "Power Supply / Ground / Ground" - MPEM Pins 2-6, 2-12 & 2-13 respectively????
3) What is "Power Supply / Power Supply / Ground / RPM signal" - MPEM Pins 1-22, 1-19, 1-18 & 1-2 respectively????

General questions:
A) How does the MPEM maintain "permanent memory" for the DESS key recognition?
B) Is there a built-in CMOS battery in the MPEM?
C) How can this CMOS battery (if it is there - last forever?).
D) IF there is a CMOS battery built into the MPEM and it dies, is the MPEM obsolete?

 

[SpitandDirt]

I'm not sure where you are pulling these wiring numbers from. I can't help you better until I have some context. Could you post the wiring diagram you are looking at?

I can tell you that the 96 XP / GSX are unique in that they have a completely separate CDI unit, made by Nippondenso of Japan, mounted in the opposite cover from the front electrical box. In the later years, the CDI unit was combined into the MPEM. Some of the wires you are describing may be the communication wires between the two devices. In addition, there is a holding relay mounted next to the MPEM that serves to provide power the CDI once the MPEM is "woke up" by the magnetic reed switch located in the DESS post and a recognized DESS key.

But as for your general questions.
A) The microcontroller is a Motorola MC68HC05 or some slightly different variant of that. I can't be certain, but I'm pretty sure the microcontroller has EEPROM capabilities.

B)No, there is no CMOS battery built into the MPEM of the 96. I don't believe any of the 2 stroke ski MPEMs have a CMOS battery from what I've seen. I have no information on the 4 stroke skis

C+D) Life span is not limited by the lack of a CMOS battery. Technically, as long as the individual components continue to function, the MPEM is not obsolete. What has caused a great deal of frustration in recent years has been the failure of the MR2535L diode, "Overvoltage Transient Suppressor Diode." Enterprising individuals will normally cut away the epoxy and replace the diode and keep going.

You can buy aftermarket MPEMs branded by WSM that are made by Arieltek of Brazil. WSM is just an importer.