Pinpoint Test G: DTC C1840 - The Scan Tool Indicates Self-Test Failure When Attempting to Carry Out the Self-Test: Notes
WARNING: This page is about a different car, the 2010 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
Refer to appropriate SYSTEM WIRING DIAGRAMS article, Vehicle Dynamic Suspension for schematic and connector information.