Hey guys,

I am pretty good with wiring and such and wondering if anyone has made their own 4rt code reader?

I know there is a yellow diagnostic port and in the manual it mentions counting flashing lights on the code reader to determine faults. I am wondering if a 12V power supply and LED could be rigged up to do the same.

Any thoughts?

I can't help feeling it must be more complex than that. Surely you need to know what the flashing lights represent - what is being read? There must be a chip to allow the diagnostic to perform?

I can't help feeling it must be more complex than that. Surely you need to know what the flashing lights represent - what is being read? There must be a chip to allow the diagnostic to perform?

I'm not so sure. I suspect that if you put 12V to that ECU pin, it puts it into diagnostic mode and outputs the signal that the diagnostic tester displays as a flashing light. If I weren't afraid to fry my ecu I may play w/it

Most little diagnostic flashers like that will use a 9v battery to power things up. 3 npins, power, ground and the signal wire. No idea what is on them.

Edited April 18, 201214 yr by copemech

Hey nerds

I made a home-built diagnostic tester that fits a Honda Montesa 4RT. Basically it is very simple to make, but I have chosen to take the full step and fit it all in one box.

As can be seen in the picture here.

But for those who really want to make a simple and inexpensive diagnostic tests and only have to read diagnostic trouble codes - I think it can be made for under 10 pounds.

Here is my approach.

Remove the plug to the condenser and connect the plug to an external 12 volt battery

Remove the plug to the fuel pump otherwise it will start.

The next thing to do is to connect a diode to 12 volts on one side of the diode and the other side must be connected to the white / blue wire that goes to ECU pin number 8 - which is called FI VARN.

In my diagnostic tests, I used a diode from the Guardian called "GWL20 12V Red Led".

So simple it can be.

To conclude, I will just say that if you start to make a tester is at your own risk.

Do not start if you are not familiar with electrical systems and their operation.

I say it again - it is at your own risk.