Why does my 2021 Highlander have poor fuel economy?

Toyota Highlander Fourth Generation (2020-present)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

4 min read

742 words

Problem Statement

Learn how to diagnose and fix poor fuel economy issues in your 2021 Toyota Highlander with our step-by-step guide.

Affected Component

fuel system

Estimated Time

2-4 hours

Symptoms

•Decreased miles per gallon (MPG) compared to manufacturer specifications.
•Engine struggles or lacks power during acceleration.
•Unusual smells or sounds from the exhaust.
•Dashboard warning lights, such as the Check Engine Light (CEL).

Diagnostic Steps

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Screwdriver or pliers
•Tire pressure gauge
•Air compressor
•Fuel pressure gauge
•Multimeter
•Basic hand tools

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Solution

Problem Diagnosis: Poor Fuel Economy in 2021 Toyota Highlander

Step 1: Gather Preliminary Information

Owner's Manual: Check the fuel economy specifications for your model.
Driving Conditions: Consider if the driving has been primarily city vs. highway, and if there are any recent changes in driving habits.

Step 2: Check for Diagnostic Trouble Codes (DTC)

Tools Required: OBD-II scanner.
Instructions:
1. Connect the OBD-II scanner to the vehicle's diagnostic port (usually located under the dashboard near the driver's seat).
2. Turn the ignition to the ON position without starting the engine.
3. Follow the scanner instructions to read any stored trouble codes.
4. Note any codes that may be related to fuel economy, such as codes for the fuel system, oxygen sensors, or engine performance issues.

Step 3: Inspect the Air Filter

Tools Required: Screwdriver or pliers (depending on the air filter housing).
Instructions:
1. Open the hood and locate the air filter housing.
2. Remove the screws or clips securing the housing and take out the air filter.
3. Inspect the filter for dirt and debris. Replace it if it appears clogged or dirty.

Step 4: Check Tire Pressure and Condition

Tools Required: Tire pressure gauge, air compressor.
Instructions:
1. Use a tire pressure gauge to check the pressure of each tire.
2. Refer to the placard inside the driver's door for recommended tire pressures.
3. Inflate the tires to the recommended pressure if they are low.
4. Inspect the tires for excessive wear or damage.

Step 5: Evaluate Fuel Quality

Instructions:
1. Check if you are using the correct octane rating as specified in the owner's manual.
2. If the fuel has been purchased from a questionable source, consider using a different station or switching to a higher quality fuel.

Step 6: Inspect Fuel System Components

Tools Required: Fuel pressure gauge, multimeter, basic hand tools.
Instructions:
1. Fuel Filter: Check for clogs or restrictions. Replace if necessary.
2. Fuel Pump: Attach a fuel pressure gauge to the fuel system to check for proper fuel pressure as specified by the manufacturer.
3. Injectors: Use a multimeter to check the resistance of the fuel injectors. Clean them if they are clogged.

Step 7: Check Engine Performance

Instructions:
1. Start the engine and listen for unusual noises or misfires.
2. Look for any signs of a rough idle or fluctuations in RPM.
3. Conduct a compression test to evaluate the health of the engine cylinders.

Repair Instructions

Step 1: Replace Air Filter (if needed)

Remove the old air filter from the housing.
Install the new air filter, ensuring it is seated correctly.
Re-secure the air filter housing.

Step 2: Replace Fuel Filter (if clogged)

Relieve fuel system pressure by removing the fuel pump fuse and starting the engine until it stalls.
Disconnect the battery.
Remove the old fuel filter using appropriate tools.
Install the new fuel filter, ensuring the flow direction is correct.

Step 3: Clean Fuel Injectors (if clogged)

Remove the fuel injectors from the fuel rail.
Use a professional injector cleaner kit or take them to a service center for cleaning.
Reinstall the injectors and fuel rail, ensuring all connections are tight.

Step 4: Replace Spark Plugs (if worn)

Remove the ignition coil or spark plug wire.
Use a spark plug socket to remove the old spark plug.
Install a new spark plug, ensuring the gap is set according to specifications.
Reinstall the ignition coil or spark plug wire.

Final Steps

Reset the OBD-II codes (if any were found and addressed).
Test Drive: Take the vehicle for a short drive to monitor fuel economy and performance.
Monitor Fuel Economy: Record MPG over the next few fill-ups to evaluate improvements.

Conclusion

If poor fuel economy persists after these diagnostic and repair steps, it may be best to consult with a certified technician or visit a Toyota dealership for further assessment. Issues like transmission problems, improper wheel alignment, or engine control module (ECM) failures may require professional intervention.