Install notes for VAG TDI ECU’s using PLCC 32 EEproms (MSA15/15.5/15.7).

Pictured below is the ECU from a 1995.5 US Jetta 4 TDI with ALH TDI engine. The two chips we’re after are the ones in the lower left corner as visible in the following picture.

Take note that the chips are indexed using a small dot on one side along with a flattened off corner (all of these are highlighted in red). The new chips MUST be indexed in the same way when installed. The ECU in the above picture has not been socketed but some ECU’s (particularly those found in MK3 chassis cars) are socketed from the factory. In the case of this MK4 ECU, the sockets had to be soldered in. Earlier ECU’s use similar sockets where the chips simply push in and can be pulled out with a PLCC extractor tool. Some have reported using a small jewelry screwdriver if you’re very careful. You do not want to break the socket or connection problems may occur. In either case, you must carefully pull/pry the old chips out and then carefully reinsert the new chips while noting the indexing on the chips along with the chip markings of H and L (H refers to the high byte and L refers to the low byte). Now go out and enjoy your new software!