Forward Collision Warning (FCW) in Honda vehicles is a driver-alert function within the Honda Sensing® suite that monitors the road ahead and warns the driver when a forward collision appears likely. On modern Hondas, FCW relies primarily on the forward-facing monocular camera (mounted behind the windshield) and—on models equipped with Adaptive Cruise/CMBS—front radar sensors.
The camera identifies vehicles, pedestrians, lane marking,s and some obstacles while the radar provides range/closing-rate data used by collision mitigation features. FCW provides visual and audible alerts and (when paired with Collision Mitigation Braking System / AEB) may initiate braking to reduce collision severity. Honda News
| Environmental interference — water on the windshield, camera/fog, sun glare, heavy rain/snow. | Severity/safety impact | Severity / safety impact |
|---|---|---|
| “FCW System Failed” or FCW/LDW amber/flash message on dash | Camera module fault, CAN communication loss, failed calibration, software fault. | Likely/common causes |
| False alerts (phantom braking, unnecessary beeps) | Camera module fault, CAN communication loss, failed calibration, and software fault. | Medium–High — nuisance or dangerous if brakes are applied unexpectedly. |
| Camera mis-recognition (glare, dirt), sensor misalignment, software algorithm regression, and radar reflection. | No alerts when hazards are present (missed detection) | High — loss of safety assistance. |
| Intermittent functionality (works sometimes) | Loose/worn wiring connectors, failing module, intermittent CAN bus errors. | Camera aiming/calibration not performed; aftermarket windshield affecting camera aiming. |
| Dashboard shows camera error codes (DTCs) or U-codes (U0073, etc.) | Communication bus faults, ground/power fault, module fault. | High — indicates electronics/communications failure. |
| System disabled after windshield replacement or collision repair | Environmental interference — water on the windshield camera/fog, sun glare, heavy rain/snow. | High — common after glass or body work; Honda requires OEM windshield and aiming procedures. |
| Error messages only in some weather/lighting (rain, glare) | Obstructed/dirty camera lens, damaged camera/radar, failed module, miscalibration, or environmental conditions. | Medium — situational but expected; usually temporary. |
Contents
Diagnostic Flowchart (text-based checklist)
- Initial safety check
- Park the vehicle on level ground, handbrake on, key off. Note the exact dashboard message(s) and when they occur.
- Visual / Quick-wins
- Inspect the windshield area around the camera for dirt, film, glazing tape, stickers, or adhesive residue. Clean with lens-safe cleaner and microfiber cloth.
- Check the front bumper/grille for damage or a missing radar cover.
- Verify no aftermarket tint/film directly in front of the camera.
- Battery and power sanity
- Check battery voltage (12.4–12.8 V at rest expected). Low battery or poor charging can throw modules into fault. Inspect battery terminals & grounds.
- Scan for DTCs
- Use a Honda-capable scanner (HDS/Honda Diagnostic System or equivalent aftermarket tool that reads manufacturer U-codes and camera DTCs). Save/print freeze frame and active/pending codes.
- Pay attention to CAN/U-codes (e.g., U0073) and camera module codes. These point to communications or module faults.
- Interpret the DTCs
- Communication codes (U-codes): check CAN bus wiring, connectors, and module grounds.
- Camera/camera-aim codes: check camera harness, connector seating, corrosion, and windshield mounting/aim.
- Radar DTCs: inspect bumper area, radar harness, and radar mount alignment.
- Electrical & connector checks
- Backprobe power/ground pins at camera/radar connectors (compare to service manual values). Wiggle test connectors while monitoring live data for dropouts.
- Inspect CAN bus continuity and short to ground/power, especially if U-codes present.
- Software/version checks
- Query module software/firmware levels using the dealer-level tool. Check for outstanding Technical Service Bulletins (TSBs) or software updates for the camera or FCW/CMBS modules.
- Calibration verification
- Confirm whether static or dynamic ADAS calibrations are required or previously performed (especially after windshield replacement, suspension changes, front-end repairs). Honda guidance indicates OEM windshield and aimed/calibration procedures.
- Functional tests
- With the scan tool and guided test mode, verify the camera image, target detection, and live data (object detection flags). Road test in safe controlled conditions to reproduce symptoms after repairs.
Troubleshooting Guide
A — Professional / Mechanic / Dealer-level procedures (assumes access to HDS / OEM tools, calibration rigs)
1. Confirm DTCs and capture data
- Connect a Honda HDS or equivalent capable of clearing/reading manufacturer codes, viewing camera image, and CAN traffic. Export logs.
- Identify primary vs. secondary DTCs (clear history, reinitialize, and see which codes come back).
2. Power & communications
- Verify 12 V supply and battery health. Use DVOM to measure voltage at the camera module connector with key ON/engine OFF; check grounds to body/chassis and the module ground circuit resistance (<0.1 Ω preferred).
- Use an oscilloscope or a high-quality scan tool to monitor CAN-H/CAN-L traffic at the camera module. Look for missing or corrupted traffic, or a bus short (dominant/idle voltages).
3. Connector & harness repair
- If intermittent CAN or power is detected, perform connector service: remove, inspect for corrosion, re-pin if damaged, apply dielectric grease, and use new OEM terminals if necessary. Replace the harness if chafing or internal damage is found.
4. Camera module inspection & replacement
- Inspect camera unit housing for water ingress, cracked optics, or impact damage. Replace the camera module with a VIN-specific OEM part if it fails or if replacement is required by the bulletin. Order a new camera using VIN (Honda guidance).
5. Radar sensor checks
- Remove the bumper to access the radar. Check the mount, connectors and radar lens for impact damage or water. Verify radar mounting height and frontal reference positions per the service manual.
6. Software & ECU updates
- Use the dealer’s software update process to install any FCW/camera module firmware updates. Some failure modes are corrected via firmware patches.
7. ADAS calibration
- Perform static calibration (target boards and alignment rig) or dynamic calibration per Honda procedures. Use OEM calibration targets or approved aftermarket systems that match Honda specifications. Verify post-calibration DTCs are cleared and the system is functional. Honda service guidance strongly recommends the OEM windshield and the specified aiming procedure after windshield or camera removal.
8. Road test with live data
- With HDS, view camera, and radar live parameters while driving in a test environment. Confirm object detection, distance estimates, and FCW alert generation. Document results.
9. Final steps & documentation
- If replaced or calibrated, log parts, recalibration method, software versions, and customer communication. Recommend drive-instructor verification if required by shop policy.
Enthusiast / DIY-friendly checks (no dealer tools)
Safety note: If live diagnosis requires module reprogramming, CAN bus work, or calibration, escalate to a dealer or qualified ADAS shop.
1. Simple cleaning & inspection (first, inexpensive step)
- Park safely, turn the car off. Clean the area of the camera behind the windshield (inside & outside) with glass cleaner. Remove any suction mounts, stickers, or applied films near the camera. Check the radar cover in the lower grill for debris.
2. Battery & obvious wiring
- Ensure battery terminals are clean and tight. If the battery is old/weak, consider replacement or charging; low voltage can cause module faults.
3. Check for obvious damage
- Look along the windshield base for cracked glass, displaced molding, or a replaced windshield with visible differences. If the windshield was recently replaced, flag calibration as suspect.
4. Read basic OBD-II codes
- Use a quality OBD-II scanner that supports manufacturer U-codes (many cheap scanners will show only generic codes). If you see U-codes or camera-related codes, note them and take pictures to bring to a pro.
5. Soft resets
- Some temporary software glitches clear after a power cycle. Disconnect the negative battery terminal for ~10–15 minutes (this can reset modules but may require radio codes or saved settings to be reentered). Reconnect and recheck. Do not remove the battery if you are uncomfortable — take it to a shop.
6. Observe behavior & collect data
- When the issue happens, note conditions: weather, time of day, whether headlights were on, recent repairs, or windshield replacement. This info is valuable to a mechanic.
7. When to stop & escalate
- If cleaning, simple connector reseating, and battery reset do not clear the failure, or if you find damaged connectors, broken camera housing, or repeated U-codes, stop and take the vehicle to a shop with ADAS calibration capability.
Best Practices & Prevention
- Use OEM windshields for vehicles equipped with Honda Sensing and insist the glass shop confirms ADAS compatibility—Honda guidance warns aftermarket glass may prevent correct camera aiming.
- After any windshield replacement, front bumper/grille work, or suspension changes, verify whether static/dynamic ADAS calibration is required and perform it if so.
- Keep the camera sightline clear: no decals, stickers, or DASH-mounted devices in front of the camera. Clean the windshield in the camera area regularly.
- Maintain a healthy electrical system (good battery, tight grounds). Many intermittent ADAS faults are rooted in marginal power or ground connections.
- Use OEM camera/camera harness parts where possible; reuse of non-OEM camera housings or aftermarket sensors increases the risk of misalignment.
- Document every repair, software version, and calibration step—modern ADAS repairs have legal/safety implications.
- Train technicians on ADAS procedures and use reputable calibration equipment (OEM or approved third-party systems). I-CAR/RTS and OEM service bulletins are good continuing education resources.
How to explain the problem & repair process to customers
Keep the explanation clear, non-technical, and safety-focused:
- “Your vehicle’s Forward Collision Warning uses a camera and sensors mounted at the front to detect hazards. Right now, the system has been disabled by a fault (we saw the ‘FCW system failed’ message and stored error codes). That means the vehicle will not warn you or automatically apply the brakes if the system detects a collision.”
- “Common causes are dirt on the camera, a power or wiring issue, module communication errors, or the camera needing to be re-aimed after glass or body repairs. We’ll start with a visual inspection and code scan, then test the camera and the wiring. If needed, we’ll update the module software and recalibrate the camera to Honda specifications.”
- “If we need to replace parts or perform a full calibration, we’ll explain parts, labor, and why calibration is necessary for your safety. Until the system is restored, drive as if the FCW/AEB features are not available and increase following distances.”
- Provide estimated costs only after diagnosis and offer to show the customer DTCs and camera live images (if available) so they can see the failure evidence.
