On my 2002 road king, i want to see if there are any trouble codes in the ECM. The Haynes manual says to bridge 1 & 2, then disconnect the negative battery cable, then switch ignition to “on”. With the negative disconnected, how can you read the codes if theres no power to light up a display?

 

I’m not sure, but I think the ECM is grounded to the frame?

 

Typical Haynes manual. I'd sure like to know how the check engine light can flash with no power....

I haven't opened one, or used one, since I threw out the one I bought for my '78 Low Rider back in the day....

You'd do well to buy/get access to a Harley Factory Service Manual and/or Factory Electrical Diagnostic Manual... I'm not near my manuals, but will look to see if I have the procedure saved on my computer.

Otherwise, someone else is sure to post up the procedure...

Is your 2002 carbureted or EFI....?

 

I have the Carbureted version here with me.... If it's EFI, you'll have to hope someone else posts up.. I can't remember the differences off the top of my head....

 

Carb

 

That’s what I thought. Haynes messed up once again. Thank you all for your input and pages from a real manual. I should buy one, the last one I bought was for my shovelhead and i think it costed me $50 back in the 80’s. But it was money well spent.

 

I just turned my ign switch to on, all i get is the oil warning light. No engine light comes on at all, even after 10 seconds.
so i would think there are codes stored, yes? We shall see. Lol. I just looked at Harley scan tools….$400.00+ damn.