2001 LS1 Cooling-Fan Diagnosis
The 2001 F-car uses two fans and three relays in series/parallel operation. Diagnose command, relay control, power feeds, grounds and motor operation as a system.
Understand the architecture first
GM describes two cooling fans and three relays arranged so the PCM can run both fans together at low or high speed.
Low-speed failure ≠ two bad motors
Because low speed uses a series path, a relay/contact/wiring problem can affect the behavior of both fans. Prove command and circuit state before replacing motors.
High-speed branch
When high speed is requested, the relay arrangement changes. Compare commanded state with actual fan operation to isolate control vs power-path faults.
Verify actual overheating
Before chasing fans, verify coolant level, temperature data and the actual overheating condition. A gauge complaint and a cooling-system fault are not automatically the same problem.
Modified-car checkpoint
Manual fan switches, rewired relays, aftermarket fan kits, radiator swaps, thermostat changes and tune changes can invalidate stock control assumptions.
DO NOT REPLACE YET
Do not replace the PCM or both fan motors because neither fan runs. Prove the shared relay/feed/ground path first.
Verification trail
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 →