Honda:

PGM-FI MIL 11 blinks (vehicle speed sensor) (Honda VTX1800C)

Turn the ignition switch to "OFF".
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Disconnect the vehicle speed sensor 3P connector. Check for loose or poor contact on the vehicle speed sensor connector.
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Connect the vehicle speed sensor 3P connector. Start the engine. Place the side stand up and keep the engine speed more than 5,000 rpm about 20 seconds or more. Put the side stand down, and check that the MIL blinks.	Does not blink →	Loose or poor contact on the vehicle speed sensor connector.
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11 blinks
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Turn the ignition switch to "OFF".
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Disconnect the vehicle speed sensor 3P connector. Turn the ignition switch to "ON". Measure the voltage at the wire harness side connector. Connection: Black/brown (+) - Green/black (-) Standard: 12 V	Out of range →	Open or short circuit in the Green/black wire of the engine sub-harness. Open or short circuit in the Black/brown wire of the main wire harness.
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Voltage exists
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Connect the speed sensor 3P connector.
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Disconnect the ECM connectors. Connect the test harness to the wire harness connectors.
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Support the motorcycle securely and place the rear wheel off the ground. Shift the transmission into gear. Measure the voltage at the test harness terminals with the ignition switch turned to "ON" while slowly turning the rear wheel by hand. Connection: Pink/green (+) - Ground (-) Standard: Repeat 0 to 5 V	Abnormal →	Open or short circuit in the Pink wire of the engine sub-harness. Open or short circuit in the Pink/green wire of the main wire harness.
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Normal
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Replace the ECM with a new one, and inspect it again.