LS1 · 2002 · COOLING FANS

2002 LS1 Cooling Fan: Command vs Temperature Diagnosis

When a car runs hot, first determine whether the PCM is requesting fan operation and whether the fan circuit responds. That separates a control/input problem from a relay/fan/power problem.

APPLICATION: 2002 Firebird / Formula / Trans Am 5.7L LS1. Do not apply fan thresholds from LT1 years.

Compare temperature input to reality

Check ECT plausibility from cold start through warm-up. An implausible input can mislead the control strategy and the technician.

Command the fans when supported

A capable scan tool can help separate the fan hardware/circuit from the temperature-based control decision. Follow the exact 2002 procedure already linked in FPV.

If commanded but not running

Move into relay, feed, ground, connector and fan-motor testing rather than replacing the ECT sensor or PCM.

DO NOT USE LT1 FAN NUMBERS

1993–1997 LT1 and 1998–2002 LS1 control strategies are kept separate. Use the exact-year LS1 material for this car.

FPV RULE

OBSERVE → MEASURE → ISOLATE → PROVE → REPAIR → VERIFY. A symptom is a starting point, not a 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.

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 →