I'm trying to get O2 sensors for my Accord, but am not sure which engine I have.
What is the difference between an A1 and an A4?
As far as I can tell the A1 = VTECH and the A4 = ULTECH, but I'm not sure.

I called my local Honda dealer, and they don't even know.

 

I just noticed the FAQ at the top of the forum list, and see that I was right about the VTECH thing.

 

yup .... it's a phone

 

Look at the logo on thevalve cover.

VTEC = F23A1

ULEV VTEC = F23A4

vtech= plug it into the phone line...

 

I'd be more inclined to plug the phone line into it... just sayin. hah. hah.

 

As has been said, look directly at the top of your engine.

If it says VTEC, it is an F23A1
If it says ULEV VTEC, it's an F23A4

If you want to be 100% certain, you could look for the stamp on the engine. It is to the left of the exhaust manifold beneath a radiator hose. Easy to see