ICP

LPS

Lockout

Low pressure / freeze

Suction dropped out the low-pressure switch.

First check

1 Prove inducer and the live code

Do not pull power — that clears the ICP PGC active code. Write LPS. Is the inducer spinning on this call? Silent inducer is not a pressure switch. Charge / leak. Filters and indoor coil first — a dirty rooftop ices like a starved piston.

Expect: 120 VAC at the inducer on a heat call. Wheel turning.

If fail: 120 VAC missing → IFC / door switch / incoming power. Voltage + dead motor → inducer.

If pass: Inducer running + this code → trap, hose, switch, vent (step 2).

The rest of the walkthrough is Diagnose.

On the plates

Charge / leak. Filters and indoor coil first — a dirty rooftop ices like a starved piston.
TXV / orifice. Economizer dumping 40 °F OA on the coil can look like a freeze-stat trip.
Do not add gas because suction is low.

Plates that use LPS

PGC
ICP/Heil/Tempstar packaged G/E · under 15 t
Diagnose PGC — Sign in

First check

On the plates

Plates that use LPS

Same number, other makers