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Diagnostic mode is a simple way to check the proper operation of most sensors and actuators on your scooter, without any special tools. There is no way you can "screw up" your scooter by accessing the diagnostic mode, the worst you can do is erasing the history of error codes, which may complicate troubleshooting if you haven't noted these codes before erasing them, assuming there are any error codes recorded in the history to begin with. WARNING: AFTER SOME THOUGHTS, I THINK THERE IS A WAY YOU CAN SCREW-UP YOUR ENGINE IN DIAGNOSTIC MODE This have to be confirmed by people with more experience than me, see my next message in this thread. Do not attempt test 30 (ignition coil) and test 36 (fuel injector) unless you have disconnected the electric supply on the fuel pump, you should also disconnect the spark-plug cap before attempting test 30. The reason this could be dangerous is that if the fuel pump is connected, fuel will be sprayed in the cylinder if you test the injector, and testing the ignition can detonate the fuel in the cylinder without the engine being cranked, regardless of the position of the crankshaft and the position of the valves. This can potentially damage the engine and other parts, and may cause personal injury as well. The other tests in diagnostic mode are safe when the fuel pump is still connected. Disclaimer: I can only take responsibility for the good results you may get from reading this guide. If you manage to screw up, then it's all your own fault. I am not a professional mechanic, I am, however, an avid enthusiast. I do as much maintenance work as I can by myself. I can change fluids (oil, coolant, brake fluid), I can do variator and clutch tuning, I can check and adjust valve clearance, etc... The only thing I am not comfortable with yet is taking apart the engine itself. I learned most of what I know from reading thoroughly the service manuals of my bikes, and being not afraid to get my hands dirty. My first scooter is a Yamaha C3 50cc 2007 that I bought that same year, my second one is a Yamaha Majesty 400cc 2007 that I bought brand new in 2009. Both are still running perfectly fine even though I tinkered a lot inside them (especially the C3). This is the extent and limits of my knowledge and expertise. The following informations are from the service manual that covers the 2005-2007 range of Majesties (model numbers: YP-400T, YP-400V and YP-400W) I have no way to know if this information also applies to more recent Majesties, although I suppose that it should be very similar, if not identical. ACCESSING THE DIAGNOSTIC MODE If you are not sure you got the process right, you can safely reset the procedure at any time by turning the ignition key to OFF and starting over the process. -Ideally, but not mandatory, you should disconnect the wire harness coupler from the fuel pump. The reason for this: During diagnostic mode, the fuel pump will turn on and off in many tests when you turn the engine stop switch on or off- The noise made by the fuel pump makes it hard, if not impossible, to hear some relays and actuators in some tests, such as : Fuel injector, fuel injector relay and idle speed control valve. In order to disconnect the fuel pump, you must remove some plastic parts. Edit: Do not attempt test 30 (ignition coil) and test 36 (fuel injector) unless you have disconnected the electric supply on the fuel pump, you should also disconnect the spark-plug cap before attempting test 30. 1-Turn ignition key an engine stop switch to OFF. 2-Press and hold the SELECT and RESET buttons. 3-Turn the ignition key to ON. 4-Keep pressing the SELECT and RESET buttons for 8 seconds or more, then release them. "dIAG" should appear on the display 5-Press and release the SELECT button to choose between CO adjustment mode (Co) and diagnostic mode (dIAG). It seems that CO adjustment mode is not available on North-American Majesties, anyway, you should not touch the CO adjustment value unless you changed the breathing of your Majesty's engine (intake and/or exhaust modification). 6-After selecting "dIAG", press and hold the SELECT and RESET buttons for 2 seconds or more, then release them. 7-Now, use the SELECT or RESET buttons to choose the diagnostic code number you want to check. The diagnostic code number now appears on the display; it ranges between 01 to 70. To increase the diagnostic code number, press and release the SELECT button, to decrease the diagnostic code number, press and release the RESET button. 8-Verify the operation of the sensor or actuator according to the list below. -Sensor operation: The value measured by the sensor appears on the display. -Actuator operation: Move the ENGINE STOP switch to ON to operate the actuator. Move the ENGINE STOP switch to OFF to stop the actuator. -You should always move the ENGINE STOP switch to OFF before you change the diagnostic code number. 9-Turn the ignition key to OFF to exit the diagnostic mode. DIAGNOSTIC MODE CODES -Diagnostic code 01: Throttle angle. This diagnostic code checks the actual value of the throttle angle with the throttle position sensor. Numbers on the display should change according to how much throttle is applied. This value is in degrees, ranging from 0 to 125. Normal values are: Throttle fully closed: 15-16 Throttle fully opened: 97-102 Diagnostic code 03: Pressure difference (atmospheric pressure-intake air pressure) This diagnostic code checks the pressure difference between atmospheric pressure and intake air pressure. In order to perform this test, you must crank the engine. To crank the engine, you must move the engine start switch to on and push the starter. Normal value is 0 to 126 during cranking. Diagnostic code 05: Intake air temperature This diagnostic code displays the temperature measured by the intake air temperature sensor. Sorry, I am not sure if this temperature is in Celsius or Fahrenheit. I suppose that it should use the same system as your Majesty was set in (Imperial for USA, Metric for Canada). Diagnostic code 06: Coolant temperature This diagnostic code displays the temperature measured by the coolant temperature sensor. Sorry, I am not sure if this temperature is in Celsius or Fahrenheit. I suppose that it should use the same system as your Majesty was set in (Imperial for USA, Metric for Canada). Note: Intake temperature and coolant temperature uses two different sensors, and the ambient temperature normally available from your Majesty's display uses a third sensor located inside the RH side of the front fairing. When your Majesty is fully cooled down, both intake and coolant temperature should be similar. If both are similar, you can reasonably assume that both sensors are not defective. For more precision, you can compare the temperature display of the intake and coolant sensors with ambient temperature measured with a thermometer nearby, or measured by the ambient temperature display normally available on your Majesty. Diagnostic code 07: Vehicle speed pulse This diagnostic code displays the incremental number of pulses received by the speed sensor located in the LH side of the front wheel hub. The range is 0 to 999, returning to 0 after 999. The number should normally increase as the front wheel is rotated. Diagnostic code 08: Lean-angle cut-off switch This diagnostic code displays the lean angle cut-off switch values. Normal readings are: Upright: 0.4-1.4 Volts Overturned: 3.8-4.2 Volts Note: The lean angle cut-off switch is a gravity operated switch designed to shut-off the engine after an accident when the scooter is laying down horizontally on either side. I don't know the exact protocol for shutting down the engine according to this sensor. According to the service manual, the lean-angle cut-off switch is triggered when an angle of 45 degrees or more is reached on either side, but such an angle can occur during normal riding, I guess. I suppose that the engine will be stopped only if two conditions are met: The lean angle cut-off switch is triggered AND the registered vehicle speed is zero. The easy way to check the operation of this sensor would be to take it off from the frame while leaving the wires connected and tilt it on either sides and check if the values showed on the display are within tolerances. The hard way would be to tilt the bike more than 45 degrees on either side and check on the display if the lean angle cut-off switch is triggered. Do not attempt this unless you are strong enough. Diagnostic code 09: Fuel system voltage/battery voltage This diagnostic code displays the fuel system voltage/battery voltage when the engine switch is ON. Range is 0-18.7 Volts. Normal value is approximately 12.0 volts. Diagnostic code 20: Side-stand switch This diagnostic code displays whether the side-stand switch is on or off. Normal readings are: ON when the side-stand is retracted. OFF when the side-stand is extended. Diagnostic code 30: Ignition coil DO NOT ATTEMPT THIS TEST IF YOU HAVEN'T DISCONNECTED THE FUEL PUMP AND THE SPARK PLUG, SEE THE WARNING ABOVE When this diagnostic code is displayed, if the ENGINE STOP switch is turned from the OFF position to the ON position, the ignition coil is activated five times per second and the engine trouble light will come on. Note: You may need an ignition checker to perform this test correctly. Sparks should be generated at the spark-plug during this test. Diagnostic code 36: Fuel injector DO NOT ATTEMPT THIS TEST IF YOU HAVEN'T DISCONNECTED THE FUEL PUMP, SEE THE WARNING ABOVE When this diagnostic code is displayed, if the ENGINE STOP switch is turned from the OFF position to the ON position, the fuel injector is activated five times per second and the engine trouble light will come on. Diagnostic code 50: Fuel injection system relay When this diagnostic code is displayed, if the ENGINE STOP switch is turned from the OFF position to the ON position, the fuel injector system relay is activated five times per second and the engine trouble light will come on. (the light is OFF when the relay is ON and vice-versa). Note: You may not hear the fuel injection system relay activation unless you disconnected the fuel pump: The fuel pump noise is much louder than the relay noise. Relays emits a clicking noise. Diagnostic code 51: Radiator fan motor relay When this diagnostic code is displayed, if the ENGINE STOP switch is turned from the OFF position to the ON position, the radiator motor fan relay is activated, as well as the radiator fan itself, five times every five seconds, and the engine trouble light will come on. Diagnostic code 52: Headlight relay When this diagnostic code is displayed, if the ENGINE STOP switch is turned from the OFF position to the ON position, the headlight relay is activated, as well as the headlights themselves, five times every five seconds, and the engine trouble light will come on. Diagnostic code 54: Idle speed control valve When this diagnostic code is displayed, if the ENGINE STOP switch is turned from the OFF position to the ON position, the idle speed control valve fully closes, then gradually opens until it is at the standby open position. This process takes approximately 12 seconds to complete. Note: You may not hear the idle speed control valve operation unless you disconnected the fuel pump: The fuel pump noise is much louder than the idle speed control valve noise. The idle speed control valve emits a vibration noise. Diagnostic code 57: Grip warmer relay When this diagnostic code is displayed, if the ENGINE STOP switch is turned from the OFF position to the ON position, the grip warmer relay is activated and the engine trouble light will come on (light is OFF when the relay is OFF, and vice-versa). Diagnostic code 60: EEPROM fault code display Displays are: 01: CO adjustment value is not properly written on or read from the internal memory. 04: Throttle valve fully closed notification value is not properly written on or read from the internal memory. 00: There is no malfunction. Note: if there is a problem displayed under this diagnostic code, your ECU (engine control unit) is probably defective. Check with your Yamaha dealer. Diagnostic code 61: Malfunction history code display Displays the codes of the history of the self-diagnostic malfunctions (Which means: A code of malfunction that occurred once but has been corrected. Different from ACTUAL codes of malfunction) If more than one malfunction has been detected, different codes are displayed at 2 seconds interval. Display range is 00 to 61. 00 is displayed if no malfunctions were detected. Diagnostic code 62: Malfunction history code delete Displays the total number of malfunction codes that are being detected by the self-diagnosis function and the malfunction codes in the past history. When this diagnostic code is displayed, if the ENGINE STOP switch is turned from the OFF position to the ON position, the HISTORY of past malfunction codes is erased, but current malfunction codes are not erased. Display range is 00 to 19. 00 is displayed when there is no malfunction. Diagnostic code 70: Control number Displays the control number of the program. No use that I can find. |
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