This procedure is for 4-pin Bike-Side Harnesses only. Check the label on your harness. A 4-pin Bike-Side Harness will have a part number beginning with 4P.

You will need a digital multimeter set to DC volts.

Before You Begin

Disconnect the USB DataLink from the Bike-Side Harness, or remove the weather-seal cap from the Bike-Side Harness connector.

Looking at the face of the connector, opposite the side where the wires enter, identify the four wire positions:

• Red
• Green
• Yellow
• Black

Make sure you are testing the correct terminals before continuing.

Test 1: Red to Black

Turn the motorcycle's ignition ON.

Measure voltage between the:

• Red wire
• Black wire

Expected result: approximately 12 V

The voltage should be solid and consistent.

If the Reading Is Low

If you see less than approximately 12 V, there may be a connection problem with the Red or Black wire.

Check that the related terminals are:

• Installed in the correct ECU connector positions
• Fully seated in the connector
• Properly locked into place
• Not loose or backed out

Also verify that the terminal orientation matches the installation instructions for your harness.

Test 2: Green to Black

If Test 1 passes, measure voltage between the:

• Green wire
• Black wire

Expected result: approximately 7-12 V

If the Reading Is Low

If the reading is below this range, there may be a connection problem with the Green or Black wire.

If Test 1 produced a solid 12 V reading, the Black circuit has already passed that test, so pay particular attention to the Green wire and its connections.

Test 3: Yellow to Black

If the previous tests pass, connect the multimeter leads between the:

• Yellow wire
• Black wire

Observe the motorcycle's fuel pump.

If the Fuel Pump Primes

If connecting the Yellow and Black terminals causes the fuel pump to prime, there is a problem with the Yellow wire or its connection.

At this point, the Black circuit has already been checked during the previous tests.

Inspect the Yellow-wire connection carefully and make sure the terminal is correctly positioned, fully seated, and locked into the ECU connector.

If Your Results Do Not Match

If any of the tests above fail, carefully recheck the Bike-Side Harness installation before attempting another ECU flash.

Pay particular attention to:

• Correct ECU pin locations
• Terminal orientation
• Fully seated terminals
• Connector locking mechanisms
• Loose or backed-out pins
• Damaged wires or terminals

If all tests pass but you are still unable to communicate with or flash the ECU, record:

• Motorcycle year, make, and model
• ECU part number
• Exact Tuning Suite error message
• Red-to-Black voltage
• Green-to-Black voltage
• Result of the Yellow-to-Black test

Questions or Concerns?

If you have any questions or concerns regarding this test or your flashing hardware, please contact us at sales@ftecu.com.

When possible, include your motorcycle's year, make, and model, ECU part number, exact Tuning Suite error message, and the results from each test above so we can better assist you.

This test requires:

• A small jumper wire or bent paper clip
• A digital multimeter set to DC volts

This procedure is for 6-pin Bike-Side Harnesses only.

Before You Begin

Disconnect the USB DataLink from the Bike-Side Harness, or remove the weather-seal cap from the 6-pin connector.

Look at the face of the 6-pin connector, opposite the side where the wires enter the connector, and identify the Red, Orange, Yellow, and Black wire positions.

The connector positions used by the 6-pin Bike-Side Harness are:

• Black = A
• Yellow = D
• Orange = E
• Red = F

Use the molded letters on the connector to confirm the positions before performing the test.

Test 1: Red and Orange

1. Turn the motorcycle's ignition OFF.
2. Use a jumper wire or bent paper clip to connect the Red (F) and Orange (E) terminals at the 6-pin connector.
3. Turn the ignition ON.

If the fuel pump primes

There is likely a connection issue with the Red or Orange circuit.

Check the related connections carefully. Make sure the terminals are:

• Installed in the correct locations
• Fully seated in the ECU connector
• Properly locked into the connector
• Not loose or backed out

If the fuel pump does not prime

Turn the ignition OFF and continue to Test 2.

Test 2: Red and Yellow

1. With the ignition OFF, remove the previous jumper.
2. Connect the Red (F) and Yellow (D) terminals.
3. Turn the ignition ON.

If the fuel pump primes

There is likely a connection issue with the Yellow circuit.

Check that the Yellow-wire terminal is installed in the correct position, fully seated, and properly locked into the ECU connector.

If the fuel pump does not prime

Continue to the voltage tests below.

Test 3: Check Orange Circuit Voltage

Set your multimeter to DC volts.

Measure between:

• Black (A)
• Orange (E)

You should see approximately 5 V and the reading should remain consistent.

Test 4: Check Yellow Circuit Voltage

Measure between:

• Black (A)
• Yellow (D)

You should again see approximately 5 V, with a reading that is consistent with the Orange-circuit measurement.

If the Voltage Readings Are Incorrect

If the readings are low or inconsistent, recheck the Bike-Side Harness installation and connections.

Pay particular attention to the Black ground connection. The ground eyelet must have a solid metal-to-metal connection with the motorcycle frame.

Do not install the ground eyelet over:

• Paint
• Clear coat
• Corrosion
• Other material that could prevent a solid electrical connection

Also verify that the Orange and Yellow terminals are fully seated and installed in the correct ECU connector positions.

If All Tests Pass

If both jumper tests and both voltage tests pass but you are still unable to communicate with or flash the ECU, the Bike-Side Harness may not be the source of the problem.

At that point, record:

• Motorcycle year, make, and model
• ECU part number
• The exact error shown in the Tuning Suite
• Whether the ECU can be read
• Results of both jumper tests
• Orange-to-Black voltage
• Yellow-to-Black voltage

Questions or Concerns?

If you have any questions or concerns regarding this test or your flashing hardware, please contact us at sales@ftecu.com.

When possible, include your motorcycle's year, make, and model, ECU part number, exact Tuning Suite error message, and the results from each test above so we can better assist you.

In the Tuning Suite, go to:

Help → Test Interface

Then check Test Inputs.

For these tests, only look at the number shown in parentheses. Ignore the colored dots.

Test 1: DataLink USB + Bench Harness

Connect only the:

• DataLink USB
• Bench harness

Do not connect the ECU or power supply.

Expected result: 37

Test 2: Connect the ECU

Connect the:

• DataLink USB
• Bench harness
• ECU

Leave the power supply disconnected.

Expected result: 0, 10, 20, or 30

Test 3: Apply Power

Connect the:

• DataLink USB
• Bench harness
• ECU
• Power supply

Turn the power supply on.

Expected result: 6, 16, 26, or 36

Understanding the Test Numbers

The hardware test uses the following values:

• 1 = Red/Ground
• 2 = Orange
• 4 = Yellow
• 10 = Green
• 20 = Brown

When troubleshooting an unexpected result, pay particular attention to the Last digit.

For example, if the ones digit is 6:

6 = 2 + 4

This corresponds to the Orange (2) and Yellow (4) circuits.

The expected results for each test are the values listed above. If your result falls outside those expected values, record the number shown and use it to help identify the affected circuit.

Questions or Concerns?

If you have any questions or concerns regarding this test or your flashing hardware, please contact us at sales@ftecu.com. When possible, include your motorcycle's year, make, and model, along with the results from each test above, so we can better assist you.

If you receive “Invalid ECU Image” / “Write Attempt Failed,” first identify which situation applies.

Stock works, unrestricted fails

If the stock file for your exact ECU part number flashes successfully, but the matching unrestricted file fails with Invalid ECU Image, the unrestricted ECU image may be invalid or corrupted.

Quick fix:

1. Open the working stock file and the matching unrestricted file.
2. In the unrestricted file, right-click ECU Mapping and select Copy.
3. In the stock file, right-click ECU Mapping and select Paste.
4. Confirm the popup shows Paste Operation Successful for the applicable items.
5. Save the modified stock file as a new file using Save As.
6. Flash the newly created file.

This keeps the known-good stock ECU image while carrying over the desired mapping changes from the unrestricted file.

Please also email sales@ftecu.com with your ECU part number, the exact stock file that works, and the exact unrestricted file that fails. This lets us locate and correct the affected file in our File Manager.

File worked before, then failed after a change

If the same file flashed successfully before and only starts giving Invalid ECU Image after you change one or more settings, save both versions.

Send us the last working file, the failing file, your ECU part number, and a description of what changed.

Stock file also fails

If the matching stock file also produces Invalid ECU Image, do not assume the workaround above applies.

Contact sales@ftecu.com so we can review the ECU, files, and flashing history.

DETAILED EXPLANATION

Hello everybody!

This post covers an issue we see fairly often: “Invalid ECU Image - Write Attempt Failed.”

A common situation is that you first download the stock file for your ECU part number and flash it successfully. Communication is good, the write completes, and your license is assigned.

You then download the unrestricted file for the same ECU part number and attempt to flash it. The write reaches approximately 99% and then fails with “Invalid ECU Image” / “Write Attempt Failed.”

WHAT THIS USUALLY MEANS

When the matching stock file flashes successfully but the unrestricted file does not, the unrestricted ECU image is the first thing we want to rule out.

Occasionally, an unrestricted file in our File Manager may contain an invalid or corrupted ECU image even though the matching stock file works normally.

The important diagnostic pattern is:

Stock file = successful

Matching unrestricted file = Invalid ECU Image

If this is what you are seeing, please email sales@ftecu.com with your ECU part number, the exact stock file that works, and the exact unrestricted file that fails. If possible, use the exact file names shown in File Manager.

Reporting the affected file pair allows us to locate and correct the unrestricted file so other customers do not run into the same issue.

HOW TO WORK AROUND IT

Before continuing, verify that the stock and unrestricted files are for the exact same ECU part number.

1. Open both files in the FTECU software.
2. In the unrestricted file, right-click the ECU Mapping folder and select Copy.
3. In the stock file, right-click the ECU Mapping folder and select Paste.
4. Verify the popup shows Paste Operation Successful for the applicable items.

Once complete, save the modified stock file as a new file. Right-click the file in the navigation tree on the left and select Save As.

Then flash the newly created file.

This uses the known-good stock ECU image as the base while carrying over the desired mapping changes from the unrestricted file. In most cases, the new file can then be flashed normally.

IF THE FILE WORKED BEFORE

Invalid ECU Image can also appear after changing a file that previously flashed successfully.

Example:

File A flashes successfully.

You make one or more changes.

You save the new version as File B.

File B now produces Invalid ECU Image.

If that happens, one of the changes between File A and File B may be causing the ECU image to become invalid.

This does not necessarily mean you configured something incorrectly. A particular setting, combination of settings, or software behavior may be responsible.

Please send us both File A and File B along with your motorcycle year/make/model, ECU part number, and a description of the changes between the files.

If possible, do not make additional changes before sending them. The closer the working and failing files are to each other, the easier it is for us to isolate the cause and provide a corrected or test file.

IF THE STOCK FILE ALSO FAILS

If the matching stock file also produces Invalid ECU Image, do not assume the map-copying workaround above applies.

This guide is primarily for the situation where the stock file flashes successfully but the matching unrestricted file does not.

If the stock file also fails, your issue may have a different cause.

Contact sales@ftecu.com with your ECU part number and the files you are working with so we can investigate further.