C1991 on 2003-2017 Ford Expedition — Lane Departure Warning System Fault
1 vehicles · 1 makes · $300-$1,500 repair
Most Reported On
C1991 is an OBD-II diagnostic trouble code meaning “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. This code is most commonly reported on 2003-2017 Ford Expedition, with repair costs ranging from $300 to $1,500.
Common Causes
Typical Repair Cost
Based on 1 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose C1991, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
FAQ
What does C1991 mean?
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.
What are the most common causes of C1991?
The most common causes of C1991 are: 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. The specific cause varies by vehicle.
How much does it cost to fix C1991?
Repair costs for C1991 range from $300 to $1,500, depending on the vehicle and root cause.
Which vehicles are affected by C1991?
Au7o has documented C1991 across 1 vehicle models from 1 manufacturers: Ford.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.