U1900 on Ford: How to Diagnose & Fix
CAN Communication Bus Fault
2 Ford models · 2 documented issues · $250-$1,400 repair
U1900 on Ford by model: symptoms, diagnosis and fix
S197 Mustangs are known to suffer from water intrusion at the cowl/windshield area that reaches the Smart Junction Box (SJB)/fuse box, leading to erratic electrical behavior. Owners report inoperative or self-activating wipers, lighting faults, battery drain, no-start conditions, and multiple unrelated electrical issues after rain or car washes. Ford published service information addressing water leak diagnosis and SJB-related corrosion concerns on these cars.
Common Symptoms
- Wipers operate by themselves or stop working
- Headlights or interior lights malfunction
- Battery drain after rain
- Intermittent no-start
- Multiple electrical accessories acting erratically
How to Fix
Inspect the passenger-side cowl, windshield seal area, body seams, and SJB/fuse box for signs of moisture, corrosion, or water tracks. Repair involves correcting the leak path, cleaning or replacing corroded connectors, and replacing the SJB if internal damage is present. Drain paths and cowl seals should be restored so the replacement module is not damaged again.
Sources for this issue (1)
The Mach-E SYNC 4A infotainment system with the 15.5-inch touchscreen experiences freezing, black screens, and spontaneous reboots while driving. Since the touchscreen controls nearly all vehicle functions (climate, charging, drive modes), a frozen or rebooting screen can leave the driver unable to adjust settings or use navigation. The system may take 30-90 seconds to reboot, during which the backup camera and climate controls are unavailable. Ford has released multiple OTA updates to address stability.
Common Symptoms
- 15.5-inch screen goes black while driving
- Screen freezes and does not respond to touch
- System reboots spontaneously showing Ford logo
- Climate controls unavailable during reboot
- Backup camera blank when screen is rebooting
- Apple CarPlay/Android Auto disconnects
How to Fix
Install all available OTA software updates — Ford has released numerous stability fixes. Perform a soft reset by pressing and holding the power button on the center screen for 10 seconds. For a full system reset, disconnect the 12V battery for 2 minutes. If freezing persists after updates, the APIM (Accessory Protocol Interface Module) may need replacement under warranty. Avoid running many apps simultaneously to reduce memory pressure.
Sources for this issue (2)
U1900 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does U1900 mean on a Ford?
U1900 stands for "CAN Communication Bus Fault." U1900 is a manufacturer-specific network code (commonly Ford) indicating a CAN communication bus fault, often a receive error. The CAN bus is the high-speed network that lets control modules such as the powertrain computer, ABS module, and instrument cluster share data. This code is set when a module stops receiving expected messages from one or more modules on the bus. Because so many systems depend on the network, a bus fault can trigger multiple warning lights and erratic behavior across systems. On Ford it is documented across 2 models: Mustang, Mustang Mach-E.
What are the most common causes of U1900?
The most common causes of U1900 are: Damaged, corroded, or loose CAN wiring/connectors, A failed or offline module pulling down the bus, Short to power or ground on a CAN line, Open circuit or broken CAN harness, Failed instrument cluster or ABS/PCM module, Low system voltage or weak battery, Water intrusion into a connector or module. The specific cause varies by vehicle.
How much does it cost to fix U1900 on a Ford?
Published repair estimates on Ford range from $250 to $1,400 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for U1900 on a different make?
View U1900 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.