C0840
Air Suspension Solenoid Valve Circuit
One of the level control solenoid valves reports an electrical fault. The corresponding axle cannot be levelled.
- Check engine light: Not always
- Emissions related: No
- Repair difficulty: medium
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Common causes
Ordered by how often each turns out to be the cause.
- Solenoid coil openCommon
- Connector water damagePossible
Parts involved
- Air Suspension Valve
- Air Suspension Module
C0840 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.