the module is under the coils, unplug the wires, unbot all three coils and unbolt the module. Make sure to use plenty of dielectric grease for a good ground
Code 42 is the ignition module faulty or loose connections.
Begin by removing the wiring harness from your 1998 Chevrolet Suburban ignition module. Remove the ignition module retaining screws. Reverse the process to install your new ignition module.
Ignition module. See if spark plug wires have arched. Check for spark. You could change it yourself. Module plus new wires will cost you around $200.
All together depending on where you go parts and labor about 722.00 : - )
How do you change the ignition control module in a 1988 Chevy Silverado 5.7L
If you have disributorless ignition it will be mounted under the coil pack . If you vehicle still has a distributor it will be in the dist.
In a 1993 Chevy Lumina, the ignition module is typically located on the ignition coil pack, which is mounted on the engine. It is usually found near the front of the engine, close to the intake manifold. To access it, you may need to remove the engine cover or other components obstructing the view. Be sure to disconnect the battery before attempting any repairs.
Check your fuses
Remove the wiring harness from your 1995 Chevy Blazer ignition control module. Remove the ignition control module retaining screws. Reverse the process to install your new ignition control module.
Disconnect the battery. Remove the ignition coils. Remove the ignition control module that was under the coils, and replace it.
3 possibilities, camshaft sensor, ignition module, sparkplugs
Bad coils or perhaps a bad crankshaft position sensor.