Low refrigerant charge from a slow leak; Faulty or out-of-range A/C refrigerant pressure sensor, or its wiring or connector; Compressor clutch not engaging, or a worn compressor not building pressure; Restricted system, such as a blocked orifice tube or expansion valve, or a blocked condenser; Poor condenser airflow from faulty cooling fans or debris blocking the condenser; Faulty compressor relay, blown fuse or damaged control wiring; Software fault in the control module where a manufacturer update exists for the model.

P1547

A/C System Performance Degraded.

GMC
Powertrain
Manufacturer code
Low severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
5: AreaVehicle speed, idle control and auxiliary inputs
47: FaultThe specific fault in that area

What it means

P1547 on a GMC means the control module has judged that the air conditioning system is not performing as expected. It compares readings such as refrigerant pressure and compressor operation against what it expects for the conditions. The exact criteria vary by model, engine and year, so check the manufacturer data for the vehicle in front of you.

Symptoms

A/C blows warm or only slightly cool air
A/C compressor cycles rapidly, or does not engage at all
Air conditioning warning or fault message on the dash, on some models
Engine cooling fans running more than normal with the A/C on
Reduced cooling at idle but better when driving

Possible causes

Low refrigerant charge from a slow leaklikely
Faulty or out-of-range A/C refrigerant pressure sensor, or its wiring or connectorlikely
Compressor clutch not engaging, or a worn compressor not building pressurepossible
Restricted system, such as a blocked orifice tube or expansion valve, or a blocked condenserpossible
Poor condenser airflow from faulty cooling fans or debris blocking the condenserpossible
Faulty compressor relay, blown fuse or damaged control wiringpossible
Software fault in the control module where a manufacturer update exists for the modelrare

How to diagnose

Read all stored codes and freeze frame data, noting A/C pressure, ambient temperature and engine speed when the code set, and check for related codes
Visually inspect the compressor, pipes, hoses and condenser for oil staining, damage or blockage by debris or leaves
Check the A/C fuse and relay, then inspect the pressure sensor and compressor clutch connectors for corrosion, damage or poor pins
With a scan tool, watch the A/C pressure sensor reading with the system off and then running, and compare it with the expected values for the model
Confirm the compressor clutch engages when A/C is requested and the cooling fans run as commanded
Measure system pressures with manifold gauges, and check vent temperatures against the manufacturer specification
Use a leak detection method such as UV dye or an electronic detector to find any refrigerant leak
Check for a service bulletin or software update for the vehicle if no fault is found

How to fix

Repair the leak, replace the faulty component, then evacuate and recharge to the specified refrigerant type and weight; refrigerant must be recovered by a suitably qualified person
Replace a faulty pressure sensor or repair damaged wiring and connectors
Replace a failed relay or fuse after finding out why it failed
Replace the compressor, along with the receiver or accumulator and the restrictor, if internal wear or contamination is found
Clear a blocked condenser, repair or replace faulty cooling fans, and clear any restriction in the system
Apply a manufacturer software update only if one is confirmed to cover this fault

Can I keep driving?

Low severity

The car is normally safe to drive, as this is a comfort system fault. Book it in soon, because running with low refrigerant can damage the compressor, and a failed compressor clutch or seized compressor can affect the belt drive.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.