Last Updated 19 April 2001
When you read this, you MAY get the impression that I am 'anti-chipping'. If so, then you are dead right. If a chipper damages your MEMCAL, then you are stuffed. Replacement memcals are not available (to the best of my knowledge) and without it, your car will not run. You have been warned !
The MEMCAL is the blue lidded module visible in the opening revealed when you remove the MEMCAL cover. To remove it, push the two clips on either end of the MEMCAL apart, and it will be levered out. Below are a couple of photos of the MEMCAL in my car.
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The second photo shows the MEMCAL with the blue plastic lid removed. This exposes the electronics within. In the upper left of the photo is the EPROM (or 'chip') containing the computer program that controls the ECU. This is identified by the GM program code AXSH2423, which is the standard program running in all 'unchipped' LC's. The device is a standard 27C256 32K by 8bit EPROM which can be read using any standard EPROM programmer. To download a copy of the binary code in my EPROM, click here. I am in the process of disassembling the code, but this isn't yet ready to be let loose on the world.
In an unchipped LC, the EPROM is soldered into the MEMCAL assembly, and cannot be removed easilly. Most garages that 'chip' cars do not have the tools required to remove the EPROM without damaging it. Therefore, they usually cut off all the pins on the original EPROM to remove it. This renders the original EPROM useless. Then, instead of soldering in a new EPROM, the 'chippers' usually solder in a socket to make changing thir new EPROM easier in the future. Their EPROM is then inserted into this socket. However, often the new socket and EPROM arrangement are too tall to allow the blue lid to be reinstalled, so it is left off. Needless to say then, a sure sign that your car has been chipped is if the blue lid is missing from the MEMCAL, or if the EPROM is in a socket.
Next to the EPROM in the MEMCAL is an ESC (Electronic Spark Control) Filter. This is an thick film analogue circuit that filters the input from the knock sensor mounted on the engine block. Apparantly there are many hundreds of different ESC filters fitted to different types of car around the world. The one in the LC is part number 1070033, and appears to be unique to the LC.
Also inside the MEMCAL are 2 chips mounted underneath the ESC filter. These aren't visible on the photos above, but trust me they are there ! These are reported to be resistor networks which can keep the car running in so called 'limp home mode' if the ECU develops a fault. The part numbers on these 2 chips are 16154201 and 16150031. Again, these two devices are believed to be unique to the LC.
The only part of a MEMCAL that can be repaired or replaced is the EPROM. All the other parts are unique to the LC, and there are no known sources of replacement parts for MEMCAL's. Complete LC MEMCALs are rarer than rocking horse manure, so if a chipper damages it, you have next to no chance of ever getting a new one, so your car will be worthless. You may be able to get a new or replacement ECU, but they do not come with MEMCAL's.