AE86 Tech #86-32: Who are you and what is your function.

There are things that we'd always wonder it's function. But for the AE86 owner, there's 3 little plugs that hang on the harness.  What the do these plugs that hang on the bulkhead do? Since I was bored, I decided to do a bit of digging.

The plugs themselves look like little squash hanging on a vine. At least for the owners of the 84-85 RWD Corollas equipped with the 4AGE engine. The 86-87 (Kouki) models, have the diagnostic box with acronyms describing the function of each terminal. It's pretty much self explanatory and can be found online.

Let's start with the biggest squash of them all.his plug has 3 female connections. 1. The chassis ground. 2. Is the power point, which is on when the car is running. 3. According to the wiring diagrams, this is the Vf terminal.  It’s part of the EFI diagnostic check.  Unlike the TE1 and E1 check, this goes a bit deeper on how the how the engine is running, are you lean or rich.   This is probably most helpful during those pesky rolling smog checks that us CommieCalifornians have to deal with ever two years.  Maybe I’ll take a deeper look into that another time.

The next one should be familiar to all owners. If not, then I recommend you sell your car now because you cannot afford nor have the know how to work on these cars. This is known as the check engine light (CEL) diagnostic connector. This was the early on board diagnostic (OBD) system.  The trouble codes can be extracted from the computer by jumping the terminals (TE1 and E1) hidden underneath the cap. There’s more information available on the web, just ask Jeeves Google it. 

 
For those with the later model (86-87) models will have a different type of connector.

O2 plug on the left, diagnostic plug on the right

Now for the last squash. Smallest of them all, it has only 1 connection terminal. This is the oxygen sensor (O2) feedback. Checking live readings of the O2 sensor can be made here.
So what can you do with these plugs? The B+ on the big plug can be used as a power point to power a work light or some other gadget.

Running air/fool fuel meters by using the power and ground on big plug and the O2 sensor plug. No cutting no mess, too bad I can't say that about the rest of the car.

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