Kymco speedometer (km/h) not work

[mikarut]

I am the owner of a Kymco Downtown 300i, year 2011, and I need technical advice regarding a difficult electrical and engine problem.

The main problems are:

1. The speedometer (km/h) does not work.

• ABS system works correctly now.
• ABS sensor has been replaced.
• The ABS control unit sends a speed signal on the grey/red wire.
• I measured the signal at the instrument cluster connector.
• The dashboard was checked by an electronics technician and he confirmed that the instrument cluster is OK.
• All other dashboard functions work normally.

1. Engine running problem:

• While riding, the engine does not go above approximately 5000–6000 rpm.
• On the stand, it can reach higher rpm.
• When TPS is connected, the ECU seems to reduce injector operation after 5000–6000 rpm.
• When TPS is disconnected, the engine behavior improves.
• TPS has been replaced and adjusted.
• Throttle body has also been replaced.
• Fuel system, injector and sensors have been checked.

I would appreciate your advice on:

• Possible ECU problem or ECU programming issue?
• Correct speed signal waveform from ABS module to dashboard?
• Any known problems on Downtown 300i models from 2011 with these symptoms?
• Recommended diagnostic procedure.

I am an experienced technician and I have already performed many measurements, so any technical information, wiring diagrams or service recommendations would be very helpful.

Thank you very much for your support.

Best regards,

Milan
Kymco Downtown 300i 2011 owner
Serbia

 

[Alan]

You've clearly already done the legwork most people skip checking the signal at the connector and having the cluster tested rather than just guessing and swapping parts blind. The rpm ceiling tied to the TPS being connected is the odd one that really does sound like the ECU is second guessing the throttle input rather than a simple wiring fault. Out of curiosity does the rpm cutoff happen the same way regardless of gear or load or only under real riding conditions like you mentioned?