DO NOT REPLACE YET
Fan failure is a circuit problem until proven otherwise
GM Chart C-12A separates PCM control from relay, feed and motor operation. A non-running fan does not identify which element failed.
LT1 · 1994 · COOLING FANS
1994 LT1 Cooling Fan Diagnosis
Prove whether the fault is command-side or power-side before replacing fans, relays, PCM or temperature sensors.
APPLICATION: 1994 Firebird / Formula / Trans Am 5.7L VIN P LT1. Use the exact option/configuration wiring for the car.
Factory control architecture
The 1994 PCM controls the cooling fans through relay-control circuits. The factory chart provides independent checks of relay control and fan operation before PCM condemnation.
Gauge hot does not equal fan fault
First determine whether the engine is actually overheating. If fans operate but coolant temperature is still excessive, move into the cooling-system branch rather than continuing to replace electrical fan parts.
Modified-car checkpoint
Aftermarket fan wiring, manual switches, PCM tuning, A/C deletion and relay rewiring can invalidate the factory circuit path. Diagnose the wiring actually installed.
Safe diagnostic order
- Confirm actual coolant-temperature concern and inspect coolant level/cooling-system condition.
- Use scan data and a capable scan tool to compare commanded fan behavior with actual fan operation where supported.
- If a command is present but fans do not respond, isolate relay control, battery/ignition feeds, relay contacts and motor circuits using Chart C-12A.
- If the electrical fans work when independently commanded but are not commanded normally, return to PCM inputs, DTCs and control logic.
- Repair the proven circuit and verify both operating modes under the exact service-manual conditions.
Exact numbers stay exact-year
FPV does not borrow later-year fan temperatures or A/C-pressure thresholds. Use the 1994 chart and calibration-specific service data for numerical switch points.
DO NOT REPLACE YET
Do not replace a fan motor, relay, PCM or temperature sensor because the fan does not run in one condition. Follow the exact-year command-versus-response path and prove where the command or current path stops.
PARTS VERDICT
Replace the fan/relay/sensor only when its exact branch fails. If scan-command, wiring, power, ground or temperature-input evidence points elsewhere, repair that cause instead.
REPAIR → VERIFY
Heat-cycle or command the system through the original failure condition, verify the expected fan response returns and confirm the engine no longer overheats because of the same fan-control fault.
FPV DIAGNOSTIC RULE
SYMPTOM → TEST → ISOLATE → PROVE → PARTS VERDICT → REPAIR → VERIFY. A code, symptom or commonly failed part is not proof by itself.
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 →