C0840 code meaning
Air Suspension Solenoid Valve Circuit
What C0840 means
C0840 is not documented anywhere in public; no list, bulletin or manual of any carmaker uses it. The title concerns the electrical side of the valves that route air in a self-levelling suspension. Some systems carry one switching valve per air spring in a central block next to the compressor, as in a Continental patent that also places fast lowering valves there; older Ford and Lincoln designs put a two-position vent solenoid on top of each spring, opened by the vehicle dynamics module to fill or vent. A circuit fault means the module sees an open, a short or wrong current on a coil. Bentley logs such a case as C11C613, an open circuit at the rapid filling valve of the Bentayga, and checks the connector first. The affected corner can no longer be raised or lowered.
C0840 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0840
- Air suspension warning or service message
- One corner sags or ride height cannot be changed
Common causes of C0840
- Most likelyWater or corrosion in the valve connector (Bentley 2064579/1 checks the plug first)
- PossibleOpen or shorted valve coil, often after moisture got into the system
- Less likelyChafed harness at the valve block or air spring
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Air suspension valveAir suspension moduleSensor wiring
What each part of C0840 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 40 | The exact fault in that area. |
What to do next
- Note C0840 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C0840
What does C0840 mean?
C0840 means "Air Suspension Solenoid Valve Circuit". C0840 is not documented anywhere in public; no list, bulletin or manual of any carmaker uses it. It is a generic code, so it means the same on every make.
Is it safe to drive with C0840?
Drive gently and only to a workshop. With C0840 the car can go into limp mode (reduced power) to protect itself.
Will C0840 fail an emissions test?
C0840 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C0840 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will C0840 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.