C1736: OBD-II code C1736 flags the air-suspension compressor relay circuit shorted to ground or open — the compressor cannot run, so the vehicle cannot self-level.

Symptoms

• The 'Service Ride Control' warning is displayed and the vehicle may sag noticeably, especially after being loaded or after sitting overnight.
• The air suspension compressor never runs even when the vehicle should be levelling itself.
• Ride height stays at whatever level the vehicle settled to; adjustments and load-levelling are unavailable.

Common causes

• A blown compressor relay fuse or an unplugged relay causing an open control circuit.
• A short-to-ground on the relay control wire preventing the suspension control module from energising the relay.
• A failed suspension control module driver that cannot pull the relay control line low to activate the compressor.

What to do?

Check the compressor relay fuse and swap in a known-good relay. Verify the suspension control module is commanding the relay on with a scan tool. Inspect the relay control wire for a short-to-ground or open. Replace the relay, repair wiring, or replace the module driver as needed.