Did a C-Code check (hold in tripometer and turn on key) yesterday and pulled 2 codes, 23 (open headlight circuit) which I assume was when a bulb went, and the mysterious code 21 which I cannot seem to find on any c-code list. Both were 46 key cycles ago according to the readout. Any ideas on what code 21 is?

 

I think Hammer posted a full list of codes some time back. They are also avail in one of the Service Manuals also

 

Yeah I've looked over lists, none of them have 21, I'd imagine its something in the headlamp circuit because it's the same amount of key cycles, but who knows!

 

It likely is related to your headlight fix if the cycles are the same.. but even if it isn't, it was 46 cycles ago, and not since.. I'd not worry any more about it..

 

I'm not worried persay, just curious as what it was.

 

Finally figured this out, 21 is dimmer switch input open, that coupled with the headlight code at the exact same key cycles stems from when I turned the key on with the headlamp/ dimmer switch pulled out while working on something!

 

Ive had a couple of c codes lately and every time i search to find the list this always pulls up, since ive read it enough times i have to agree i never found a 21, glad you got it fixed!!