Thread: OBD2 -> OBD1 stepdown harness diagram

I figure if I solder the wires and get a good connection I should be ok. Just have to keep a clear mine...

You technically could crimp it onto the wiringharness. I think I'm going to do that eventually to avoid the whole stepdown bs.

I thought about that, then you doing all that work on the floor of the car in a tight space. Then if the car ever goes back to stock for some reason, you can drop in a stock ecu with no issues.

So i'v run into a small issue, OBDI does not have a wire coming out of slot 111, do i need to add the wire in there or does it not need to be connected. It does show in the diagram that OBDI 111 needs to be connected to OBDII 115.

On the OBDI diagram it shows 111 as a Heated Oxygen Sensor and on the OBDII side it shows Front Heated Oxygen Sensor...

I don't trust my step down for long term purpose. Especially the solder, once you start soldering you'll understand better.

That's very odd that you dont have that wire! Make sure you got it traced properly .

Tomorrow I may go to the junk yard and check out another harness to see if that wire is missing or what. The more I look at the B14 ecu and having to connect wires to it the more I understand why you want to do whAT You want to do. If my car wasn't my daily, I would definatly consider. Who knows I may do the step dawn then later down the road do what you mentioned. Do you have a stepdown now? If so can u check out pin 111 on the OBDI side.

Thank you Vadim



quick picture, notice 111 has no wire. front row slot 3

Something to keep in mine, when staring at the pinouts, they will be showing the ECU side. Now there is a good chance it might be missing the heater (due to the age of the ECU harness). In that case just pull another pin out and add it to the correct location.

So let's say 91-92 vs 93-94 would or would'nt have the heater line, does that go for the ECU as well?

Well I'm running a 92 ecu, not sure about the year of the plug though. As far as I know the header seems to be working fine .

Hi guys,
Im having a problem with my conversion harness, i bought it some time ago, and now that im using it, the car does not shut down when i remove the key, to explain a little bit more, i remove the key to turn off the car, and the engine still working.. dont know what to do... now i had to push the brakes and then in 1st gear get my foot of the clutch to turn the engine off, later i have to remove the ECU by hand... im sick of doing that... does anyone knows what could be wrong with the conversion harness?

Thanks,