C1991 on Ford
Lane Departure Warning System Fault
C1991 on Ford vehicles indicates lane departure warning system fault. Au7o has documented this code across 1 Ford model — most commonly on Expedition. This is a manufacturer-specific chassis/safety code indicating a fault in the Lane Departure Warning (LDW) system. Lane departure warning uses a forward-facing camera (and on some vehicles related modules) to detect lane markings and alert the driver if the vehicle drifts out of its lane. C1991 sets when the system's module detects an internal failure, a sensor/camera problem, or a condition that prevents reliable operation. The lane-departure feature may be disabled and a warning indicator may appear, while basic driving is unaffected. Typical repair costs on Ford range from $300 to $1,500, depending on the specific model and root cause.
Common Causes of C1991
- •Blocked, misaligned, or dirty forward camera/sensor
- •Faulty lane departure warning camera or module
- •Windshield replacement requiring camera recalibration
- •Wiring or connector fault to the camera/module
- •Low system voltage or power/ground issue
- •Software/calibration fault needing an update or relearn
- •Communication (network) fault with the camera module
C1991 on Ford by Model
Ford Expedition(1 issue)
- Air Suspension Compressor Failure and Rear Sag2003-2017
The 2003-2017 Ford Expedition with optional air suspension (standard on Eddie Bauer, King Ranch, Platinum, and EL/MAX trims) suffers from air suspension compressor failure, air spring leaks, and ride height sensor malfunctions. The compressor, located under the vehicle, is exposed to road debris, salt, and moisture which degrades the motor and valves. When air springs develop leaks, the compressor runs continuously trying to maintain ride height, leading to premature burnout. RepairPal estimates compressor replacement between $666 and $724, though dealer pricing can reach $1,200. NHTSA has received hundreds of complaints regarding air suspension failures. Strutmasters.com notes that 2007-2011 Expedition and Navigator share the same air suspension system and failure patterns. Many owners opt for air-to-coil spring conversion kits as a permanent, lower-cost solution.
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View C1991 across all makes →Frequently Asked Questions
What does C1991 mean on Ford?▼
C1991 stands for "Lane Departure Warning System Fault." This is a manufacturer-specific chassis/safety code indicating a fault in the Lane Departure Warning (LDW) system. Lane departure warning uses a forward-facing camera (and on some vehicles related modules) to detect lane markings and alert the driver if the vehicle drifts out of its lane. C1991 sets when the system's module detects an internal failure, a sensor/camera problem, or a condition that prevents reliable operation. The lane-departure feature may be disabled and a warning indicator may appear, while basic driving is unaffected. On Ford specifically, this code is documented across 1 model.
What causes C1991 on Ford vehicles?▼
Common causes on Ford: Blocked, misaligned, or dirty forward camera/sensor, Faulty lane departure warning camera or module, Windshield replacement requiring camera recalibration, Wiring or connector fault to the camera/module, Low system voltage or power/ground issue. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix C1991 on a Ford?▼
Repair costs on Ford range from $300 to $1,500, depending on the specific model and root cause.
Which Ford models have C1991 documented?▼
Au7o has documented C1991 on 1 Ford model: Expedition.