LT1 · 1994 · OBD-I / DISTRIBUTOR
1994 LT1 Diagnostic Architecture
1994 remains an OBD-I LT1. GM revised the distributor-ignition diagnostic chart for 1993–1995 F-cars, reinforcing that the ignition system must be isolated circuit-by-circuit.
APPLICATION: 1994 Firebird / Formula / Trans Am 5.7L LT1 only. Use the actual 1994 fan/distributor configuration on the car.
Use the revised DI logic
- Verify the basic diagnostic system check before entering ignition diagnosis.
- Separate spark output from cap/rotor/wires, coil/primary feed and distributor-to-PCM reference information.
- A low-resolution reference problem and a secondary ignition problem are different branches.
1994 configuration matters
- Do not assume one cooling-fan layout: identify the actual relay architecture before fan diagnosis.
- Do not import 1996 OBD-II P-codes or later vent-system expectations into the 1994 car.
Crank/no-start order
- Confirm battery/cranking condition and fuel in tank.
- Check PCM/system operation and security state.
- Establish spark, injector operation and actual fuel pressure.
- Only then isolate the failed subsystem.
DO NOT REPLACE YET
No-spark does not equal distributor. A revised factory chart explicitly separates coil/primary, secondary and distributor-reference paths.
FPV DIAGNOSTIC RULE
OBSERVE → MEASURE → ISOLATE → PROVE → REPAIR → VERIFY. A code or symptom identifies the next test, not the part to buy.
AFTER THE FAILURE IS PROVEN
Use the proven failed branch—not the original symptom—to choose the replacement. Go from diagnosis to the Parts Verdict →