There are ways to troubleshoot a 1993 Chevrolet pick-up's engine by sight, sound, and checking for symptoms while you drive, but sometimes that can be time consuming, especially if you are not sure of all the symptoms have presented themselves. In many cases, the truck's On-Board Diagnostic system can be of great assistance. It will direct you to where the Chevy's computer is detecting problems. Because 1993 Chevy trucks predate the current standardized diagnostics, you will have to rely on the old system, which is known as flash code. It is not difficult to do.
Open the driver side door and locate the Assembly Line Data Link. It will be beneath the dash and near the fuse panel.2
Unbend a paper clip until it's straight, and then bend it into a long, tight "U" shape.3
Insert the "U" shaped paper clip into the ALDL port. The port features twelve slots, and the paper clip needs to connect two slots on the top row, to the far right. One will be at the end of the row, and the other will be to its immediate left.4
Turn the Chevy pick-up's electrical system on. You do not need to crank the engine.5
Count how many times the check engine light flashes. General Motors flash codes are two digit sequences. Numbers in the sequence will be separated by a short pause. For example, code 15 will consist of one flash, a pause, and five more flashes. A longer pause will separate the end of one code and the beginning of a new one. The first code relayed will always be "12." It is safe to ignore this. Write the code numbers down.6
Turn the electrical system off once the codes have finished. Remove the paper clip from the ALDL.7
Look up the codes online. While owning a Haynes repair manual for Chevy pick-ups is very useful, you can find the code descriptions online for free.8
Open the Chevy's engine compartment, and start the troubleshooting process based on the flash codes and their definitions.