LT1 · 1997 · COOLING / FAN CONTROL

1997 LT1 Cooling-Fan Diagnosis

Separate an actual overheating problem from fan-command, relay, motor, power/ground and airflow faults on the exact 1997 LT1 application.

APPLICATION: 1997 Firebird / Formula / Trans Am 5.7L LT1 (VIN P); exact-year cooling-system and PCM fan-control information.

SYMPTOMMake the failure repeatable.

TESTMeasure the system in the failed state.

ISOLATESeparate input, control, output and mechanical branches.

PROVEDemonstrate the failed branch before buying parts.

REPAIRRepair the proven cause.

VERIFYRepeat the same test state after repair.

Start with the complaint

Fans never run, only one operating state is present, fans run constantly, and the engine overheats with apparently working fans are different faults.

Prove temperature data

Before blaming fan hardware, make sure the PCM is receiving plausible coolant-temperature information and that the engine is actually at the condition being diagnosed.

Command vs power stage

Separate PCM request from relay switching, fan-motor power/ground and motor/mechanical condition. A commanded fan that does not run is not the same fault as a fan never commanded.

Cooling-system branch

If the fans operate but temperature still climbs, move to coolant level/condition, pressure integrity, airflow, thermostat/flow and mechanical engine causes instead of continuing to replace relays.

Modified-car checkpoint

Lower-temperature thermostats, fan-switch/tune changes, aftermarket radiators and added fan wiring can change expected command behavior. Record calibration and wiring changes before interpreting the system.

DO NOT REPLACE YET

Do not replace fan motors, relays, ECT sensor or PCM from temperature alone. Prove which side of command-to-output failed.

FPV DIAGNOSTIC RULE

SYMPTOM → TEST → ISOLATE → PROVE → PARTS VERDICT → REPAIR → VERIFY. A DTC, gauge reading or symptom chooses the next test; it does not choose the part.

1997 starting/charging →1997 diagnostic architecture →Exact year navigator →Start over by symptom →

PUBLISHABLE SOURCE

Exact-year verification trail

1997 Pontiac Firebird LT1 service manual — Repair and Diagnosis

This page intentionally omits hard values that are not reproduced from an exact-year source on the page. Use the linked exact-year service information for connector-level tests, pinouts and numerical limits.

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 →

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.