How to Diagnose and Fix a Knocking Noise in Your Honda Fit

How to Fix Knocking Noise

A knocking noise from your 2020 Honda Fit can be alarming, but it's often related to specific, fixable issues. Based on real owner reports, these noises frequently stem from parts like the oil pan lip, suspension components, or corrosion-related problems, especially after exposure to winter conditions. Addressing it promptly can prevent further damage. As one owner dealing with a similar undercarriage issue noted, "Really would like to avoid paying $200 if I can, but also don’t want salt destroying everything underneath in winter." This highlights the balance between cost and protecting your vehicle.

Symptoms

Owners describe a variety of symptoms that accompany or indicate the source of a knocking noise. A common theme is a sound that occurs during specific conditions, such as driving over bumps, during acceleration, or when turning. The noise is often described as a metallic clunk, a repetitive knock, or a concerning rub or scrape from underneath the vehicle.

You might also notice physical signs correlated with the noise. This includes visible damage or misalignment of underbody components like splash guards or the oil pan lip. After winter driving, increased corrosion on metal parts like the battery terminals or suspension components can lead to poor connections and unusual sounds. In some cases, the noise may be tied to recent modifications, where a new part isn't fitting correctly with existing components, causing interference.

The environment plays a significant role. Owners in snowy regions report a marked increase in these issues due to road salt accelerating corrosion and potentially damaging protective underbody panels. The noise might be intermittent at first, occurring only on certain road surfaces or when the chassis is under a specific load, but it can become more constant if the underlying cause is not addressed.

Most Likely Cause

The most likely cause of a knocking noise in the 2020 Honda Fit, based on owner discussions, is interference or damage to underbody components, particularly the oil pan lip or splash guards. These parts are vulnerable to impact from road debris, speed bumps, or accumulated snow and ice. When bent or cracked, they can contact other parts of the drivetrain, suspension, or the road surface itself, creating a distinct knocking or scraping sound.

This problem is exacerbated in winter. Road salt causes corrosion, which can weaken mounting points and brackets. A loose or corroded splash guard or a slightly bent oil pan can move out of position, leading to that troubling noise. Furthermore, attempts at DIY modifications or installing non-OEM parts without proper test-fitting can create similar interference issues, as parts not designed for exact fitment may contact surrounding components.

How to Diagnose

Diagnosing a knocking noise requires a systematic approach to isolate the source. You will need a few basic tools: a flashlight, a set of socket wrenches, jack stands, and a floor jack. Never rely solely on the vehicle's jack for safety. Start by noting when the noise occurs—is it over bumps, during acceleration, or at all times? Try to replicate the sound by slowly driving over a known bump in a safe, empty parking lot.

Safely lift and secure the vehicle on jack stands. With a good flashlight, perform a thorough visual inspection of the entire undercarriage. Look for obvious signs of impact on the oil pan, which is typically a black aluminum component at the lowest point of the engine. Check all plastic splash guards and underbody panels for cracks, loose fasteners, or sections that are hanging down. Look for shiny, scraped metal or plastic—this is a telltale sign of contact.

Pay special attention to areas showing heavy corrosion, especially around mounting brackets. Check the suspension components—control arms, sway bar links, and struts—for excessive play by trying to move them by hand (a pry bar can help check bushings). Also, inspect the exhaust system for loose hangers. If you've recently made any modifications, double-check the clearance around the new parts. As one modifier wisely advised regarding fitment, "Note: if you have a FMIC that uses a top center mount and choose to get this set. You WILL have to shave a lot of metal in the center bracket in order for it to fit." This principle applies to any new part; improper clearance is a direct path to noise.

Step-by-Step Fix

If your diagnosis points to a damaged oil pan lip or a loose underbody panel, here is a step-by-step guide to address it.

1. Gather Parts and Tools: Secure a replacement splash guard or oil pan if necessary, along with the correct fasteners. You'll need your jack, jack stands, socket set, screwdrivers, and possibly a trim removal tool.

2. Safely Elevate the Vehicle: Park on a level surface, engage the parking brake, and chock the rear wheels. Lift the front (or relevant corner) of the vehicle with your floor jack and place it securely on jack stands. Never work under a vehicle supported only by a jack.

3. Remove the Damaged Component: Locate all the fasteners (typically plastic clips, Phillips-head screws, or 10mm bolts) holding the affected splash guard or panel. Remove them carefully. If the oil pan itself is cracked or severely dented, this is a more advanced repair requiring oil drainage and potentially dropping the subframe—consider professional help for this.

4. Inspect and Prepare the Area: With the panel removed, inspect the mounting points on the vehicle's frame. Clean any debris or heavy corrosion from the threads. If the oil pan lip is only slightly bent and not leaking, you may carefully bend it back into position using a hammer and block of wood to avoid further damage. The goal is to restore clearance.

5. Test-Fit the New Part: Before fully installing, loosely position the new splash guard or confirm the straightened oil pan has clearance. Ensure it doesn't contact any moving parts, the exhaust, or the drivetrain. As one owner looking for parts emphasized, the search is for something that "won’t slide around" and fits the space perfectly. Proper fitment is critical.

6. Secure the Component: Once satisfied with the fit, install all fasteners. Tighten bolts to a snug fit but avoid overtightening, especially into plastic retainers. Ensure the panel is flush and secure.

7. Lower the Vehicle and Test: Carefully lower the vehicle to the ground. Remove the wheel chocks. Take a short test drive over the same routes that previously caused the noise. Listen carefully for any recurrence.

8. Address Corrosion: Since this is often a winter-related issue, consider applying a rust inhibitor or undercoating to vulnerable areas to prevent future corrosion and bracket failure. This proactive step addresses the root cause mentioned by owners worried about salt destruction.

Parts and Tools Needed

• Replacement Splash Guard / Underbody Panel: Honda OEM part is recommended for guaranteed fitment. Check part numbers based on your specific trim (LX, EX, Sport).
• Oil Pan: (If cracked) Honda OEM oil pan assembly and a new gasket/sealant.
• Fasteners: Assortment of the specific plastic push clips, screws, or bolts used for your underbody panels. These often break during removal.
• Tools: Floor jack, (2) Jack stands, Wheel chocks, Socket set and ratchet (typically 10mm, 12mm, 14mm), Screwdrivers (Phillips head), Torque wrench, Flashlight or work light, Trim removal tool, Hammer and block of wood (for minor bending).

Real Owner Costs

The cost to fix a knocking noise varies dramatically based on the cause and who does the work.

• DIY (Splash Guard Replacement): This is the most common and affordable fix. A new OEM splash guard can cost between $50 and $150. Fasteners may add $10-$20. If you already have the basic tools, your total cost is just the part. As reflected in owner sentiment, the goal is often to "avoid paying $200" for a simple panel.

• Professional Repair (Splash Guard): A shop will charge for the part (at a markup) and 0.5-1.0 hours of labor. Total cost can easily range from $150 to $300, hitting the price point owners hope to avoid.

• Professional Repair (Oil Pan Replacement): This is a major repair. The oil pan itself can cost $150-$400. Labor is intensive, requiring oil drainage, part removal, and resealing. Total shop costs can range from $500 to $900+ depending on labor rates.

• Suspension Component Replacement: If the noise is from a worn control arm or sway bar link, part costs range from $100-$300 per component, with 1-2 hours of labor. Total professional cost typically falls between $250 and $600.

Prevention

Preventing knocking noises centers on protecting the undercarriage and being mindful of modifications.

1. Winter Preparation and Cleaning: Before winter, apply a quality fluid film or rubberized undercoating to metal components to resist salt corrosion. During winter, regularly wash your vehicle, including a thorough spray underneath to remove salt buildup.
2. Drive Mindfully: Be cautious over speed bumps, potholes, and steep driveways. The 2020 Honda Fit has modest ground clearance; scraping the undercarriage can bend components.
3. Secure Modifications: If you install any aftermarket parts, especially suspension components, ensure they are designed for your exact model and year. Double-check all clearances and torque all fasteners to specification. The fitment issues highlighted by owners swapping suspensions—"Will these fit my 2019 JL?"—are a cautionary tale.
4. Regular Visual Inspections: Periodically, perhaps during an oil change, take a look underneath. Check for loose panels, signs of new scrapes, or developing corrosion. Catching a loose clip early is a simple, free fix.

What Owners Say

Real experiences from HONDA owners:

Owner Experiences

"Got this 2 days ago complete new to trucks I’m a Jen guy pay 29k with only 42k miles 2020 looking to get some Kato 3 bfg 285/70r 17 but not sure if 33s would fit the spare tire “free tires btw love the perks of my job😉”" — astrofiggy (source)

"Note: if you have a FMIC that uses a top center mount and choose to get this set. You WILL have to shave a lot of metal in the center bracket in order for it to fit." — AceCubesMcfrost (source)

"Factory Rubicon suspension on unlimited sport? There's a local guy selling a set of Rubicon fox shocks control arms and springs from a 2020 Rubicon JT and claims they only have 2000 miles on them." — djdb05 (2,000 miles) (source)

Real Repair Costs

"Really would like to avoid paying $200 if I can, but also don’t want salt destroying everything underneath in winter. Any suggestions or leads would be appreciated!" — Dry_Preference1208 (source)

"Or maybe a universal fit that works? Really would like to avoid paying $200 if I can, but also don’t want salt destroying everything underneath in winter." — Dry_Preference1208 (source)

"Had my $125 Amazon one since 2020, and it's flawless except for where I broke it pushing stuff in that didn't fit. Good news is they're still $125, so if it ever quits latching I'll replace it for cheap." — asbestoswasframed (source)

FAQ

Q: Can I drive my Honda Fit with a knocking noise? A: It depends on the severity. A light scrape from a loose splash guard might be okay for a short, careful drive to a shop. However, a loud, metallic knock from the suspension or drivetrain could indicate a serious safety issue like a failing joint or bracket. It's best to diagnose immediately and avoid driving until you identify the source.

Q: Is this a common issue on the 2020 Honda Fit? A: While not a universal design flaw, knocking from underbody panels is a common occurrence across many compact cars, including the Fit. Its low ground clearance makes it susceptible to impacts. Issues related to winter corrosion are also common in regions that use road salt.

Q: DIY vs mechanic—what's recommended for this fix? A: If the issue is a simple, accessible plastic splash guard that you can identify, replacing it yourself is a very achievable DIY project that can save significant money. However, if the noise is linked to the oil pan, suspension, or requires complex disassembly, a professional mechanic is strongly recommended. Misdiagnosis or improper repair of these components can lead to oil leaks or unsafe driving conditions.

Q: How long does it take to fix a loose splash guard? A: For a DIYer with the correct replacement part on hand, the job typically takes 30 to 60 minutes. This includes safely jacking up the vehicle, removing the old panel, and installing the new one. A professional shop would likely complete it in under an hour.

Q: Could the noise be related to my battery? A: Yes, indirectly. Owners mention checking the battery negative terminal. Severe corrosion at the battery terminals can cause electrical gremlins and, in rare cases, a poor ground might affect sensors in a way that could be misinterpreted. However, a physical "knock" is almost always a mechanical contact issue. Always check for a tightly secured battery and clean terminals as part of general maintenance.

Q: I installed new parts and now hear a knock. What should I do? A: This strongly points to an installation or fitment issue. Revisit the installation instructions and check all fastener torques. Look for any contact points between the new part and the vehicle's body or other components. As one owner's experience with modifications shows, sometimes "you WILL have to shave a lot of metal" for proper fitment. You may need to uninstall and check for required modifications or contact the parts manufacturer for guidance.