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Diagnosing Yamaha’s EFI Self-Diagnostic Systems


For years now technicians and educated vehicle owners have enjoyed the benefits of the self-diagnostic functions of fuel injection systems. Evaluating fault codes is now a standard task in powersport vehicle service. Some fuel injection systems have expanded onboard diagnostic abilities that can be used to troubleshoot issues in addition to the simple fault codes.

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1. yamaha uses a diagnostic mode that can be accessed with the multifunction display2. inspect a faulty tps with the diagnostic mode3. electrical circuits can be activated and checked with the multifunction meter.4. The diagnostic mode can be used to operate sensors and actuators.


1. recently produced online service manuals for the Yamaha Raptor 700R sport ATV and WR250R dual sport motorcycle. These models, along with many other recent Yamaha vehicles, have a diagnostic mode that can be activated with the multifunction display. This diagnostic mode goes beyond just being able to read fault codes – it can operate sensors and actuators to troubleshoot the vehicles components and circuits. 


Like most fuel injection systems, the ECU can detect and store fault codes if it detects something amiss. Once the code has been expressed, the next step is to check the fault code number against the diagnostic trouble code (DTC) table to identify the suspect malfunction. The DTC table provides the symptom and probable cause of the fault code; all pretty typical so far for fuel injection troubleshooting. What’s new is a diagnostic code number that is provided with each relevant fault code. 


2. The fault code is the detected problem. For example fault code 15 is a faulty throttle position sensor/circuit. Its diagnostic code is d01. The diagnostic code is the code used with the diagnostic mode to troubleshoot the particular item. Consult the sensor/actuator operation table in the service manual for more information on using the specific diagnostic codes.


When d01 is activated in the diagnostic mode, the multifunction display will show a numerical value to indicate the throttle position. The sensor operation table has specific ranges for this throttle position number at throttle open and closed positions. The TPS and its circuit should be inspected in greater detail if the indicated number is outside of the specified range. 


This type of troubleshooting data analysis has typically required the connection of a special tool to the vehicle. Having this type of technology onboard is a huge advantage in that no expensive special tools must be purchased, and the diagnostics can be performed anywhere as long as one has access to the correct information. Note, the 2006 – 2008 and 2013 and newer Raptor 700 models do not have an LCD multifunction display, and they still require a special tool to use the diagnostic mode.


3. In addition to sensor troubleshooting the diagnostic codes can also be used to operate circuits and actuators to check system functions. Want to know if the radiator fan motor circuit is functional? Select the d51 diagnostic code to actuate the radiator fan motor relay repeatedly. This should cut the fan on two seconds, off for three seconds and repeat this cycle five times. If the fan or relay fails to operate this indicates a problematic component or circuit that needs to be inspected further.

4. The system can operate the fuel injector, fuel pump relay, ignition coil, EXUP valve and others all with the multifunction display. One only needs to have the information to use the diagnostic mode and be able to interpret the results. No special FI tool needed, and no need to pick up a multimeter until one has allowed the vehicle to diagnose itself. 

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