Code Definition

C1840 — Air Suspension Disable Switch Circuit Failure

System: Chassis  |  Type: Manufacturer-Specific  |  Make: Ford

About C1840

C1840 is a manufacturer-specific chassis diagnostic trouble code recorded for Ford vehicles. It belongs to the C-prefix family of codes, which covers chassis, braking, steering, suspension, or stability-control faults.

When C1840 is stored, the module has detected an electrical-circuit fault in the wiring, connector, or driver associated with the named component.

Scanning & clearing: Chassis (C) codes are stored in the ABS, traction control, or stability-control modules. An enhanced or OEM-level scan tool is usually required to read and clear them.

C1840 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

DTC C1840 is a manufacturer specific chassis code used on Ford and Lincoln vehicles fitted with air suspension, including the Town Car, Expedition, and Navigator. These vehicles have an air suspension disable switch, usually located in the luggage compartment or behind a side trim panel, which allows the system to be switched off before towing, jacking, or hoisting the vehicle. The air suspension control module monitors the state of this switch circuit, and sets C1840 when it detects an open circuit or an implausible signal that prevents it from determining the switch position. When the code i...

Join TaT to view the complete code information and diagnostic details.

Quick Facts