Code 42 relates to the Electronic Spark Timing (EST) system.  The computer puts out a square wave timing signal to the ignition module..  It also puts out a 5v 'Bypass' signal.  The bypass voltage causes an electronic switch in the module to click over to EST.  Without the 5v it's in the 'Bypass' position and runs off internal base timing.  In bypass the EST signal is pulled low by the module and in the EST mode, it is not. 

The following picture illustrates.  Top is bypass and bottom is EST.



Something as simple as setting the ignition timing will set the code 42 because the bypass is unplugged to force base timing for adjustment.

Otherwise, the switch in the module was not following command, wiring , or computer problems.  I suggest just clearing the code and see if it comes back.  Probably not related to your 'flare'

If you need to find a qualified technician in your area with good access to information resources you may use this tool:

http://www.iatn.net/dir/search.asp