Use what disappears during the failure to choose the branch. Do not start with an Optispark purchase.
If both are missing, move upstream into PCM power-up, security/fuel-enable state, distributor reference information and ignition-control circuits. If injector operation remains but spark is gone, the branch changes toward ignition output.
GM's 1993 ECM wiring identifies separate low- and high-resolution distributor inputs. GM also issued a revised DTC 36 distributor chart for 1993 F-body LT1 cars, so the latest applicable chart controls.
A cranking RPM indication can show that some reference information exists, but it does not prove the ignition-control path, coil output, injector enable, or secondary distribution are healthy.
PASS-Key II is part of the 1993 starting architecture. If the security state or fuel-enable path is abnormal, diagnose that system before buying fuel or ignition parts.
GM Bulletin 316528 revised the 1993 F-body LT1 DTC 36 distributor diagnostic chart. FPV does not substitute a later-year chart or a generic Optispark test for that exact-year strategy.
Do not replace the fuel pump, ignition parts, security components, PCM or sensors just because the engine cranks but will not start. First prove which required input—fuel, spark, injector command, synchronization or enable—is missing.
Replace only the component/circuit that fails its dedicated test. A no-start is a system state, not a parts verdict.
After repair, verify cold and hot restart, confirm the engine starts without extended crank, and recheck for returning DTCs or loss of the same required input.
SYMPTOM → TEST → ISOLATE → PROVE → PARTS VERDICT → REPAIR → VERIFY. A code, symptom or commonly failed part is not proof by itself.
Use the proven failed branch—not the original symptom—to choose the replacement. Go from diagnosis to the Parts Verdict →