I'm pretty sure you're right about something being broken. What I don't yet have enough information to assess is whether or not it's something I did inside the CPU, or something external to the CPU that I enabled it to tell me by fixing it. Without a schematic it's hard to tell what's supposed to be grounded and open, where, and when.

My lock barrel is super worn (I can start the car with a penny and pull the key out at any time), so the key warning with the door switch as a component holds water and had not been considered.

Is the one in the manual the posh trim or the pauper trim? I saw in a manual just two days ago a schematic for an RX7 CPU that included a door beeper (among other things). I should have taken a photo with my phone, but the guy said he had a PDF of a better manual that also broke them down by year and he would email it to me (which hasn't happened yet).

 

Responding to Satch now:

That sort of connection to the diagnostic cluster is exactly the sort of thing that makes this as challenging as it is. My diagnostic cluster is all kinds of toasty inside (see my build thread, it's like a science experiment in there), so a connection there could be the short that's causing my problem.

 

unplug it, and see what changes.

 

The weather has not been my friend... I sort of stumbled into a spare CPU, plugged it in, and it looks like whatever was causing it to beep was internal. The new CPU is only partially functional, but at least it's not beeping and the important stuff seems to all be working. Must have shorted something when I resoldered it. I haven't had a chance to dig in and see where I did what, but it'll happen sooner or later... Other things are higher priority at the moment, and I'm way behind everything with all the goddamn rain...

 

I have known it for years but have never addressed the issue with my own cpu, but bad capacitors screw up the cpu. I bet everyone could pull the boards out of their cpus and there will be capacitor crust on their cpu's less they have been rebuilt already.

 

OK! I finally managed to dig into this a little deeper. I checked the CPU out to some degree looking for shorts and found none. I rigged up a way to test individual wires in the plug to see which one was causing the annoying noise, and I figured out which wire it is... Unfortunately, the wiring diagrams are not... Or maybe I'm not good enough. I don't know. Whatever the shortcoming, I can't figure out where to look down the line to try to stop whatever short I'm having.

The wire in question is thicker, and green with a white stripe. The third from the top left here:



I tested it for continuity to ground, and that's what it does. Here's the schematic in case anyone is brighter than me...



I have an '86 NA "luxury" pkg car, so I don't have an ignition light, door light, or courtesy lights in the doors (which is what I think is going on there). If anyone can help me figure out where to look for the short, it would be appreciated.

 

I realized the door lock cylinder light and the courtesy lights (I'm pretty sure that's the lights in the door panels that I don't have) are all on the door harnesses, which go through holes that could very easily lead to chaffing. I pulled the plugs between the main harness and the door harnesses and tested the G/W wire for continuity... and it's still shorting.

I don't have a lock cylinder light, and I don't see where there would be provisions for it... My steering column cover is broken, and the key warning switch is probably broken (the barrel is very worn), but there doesn't seem to be anything missing there. Did those exist in '86? I'm sure even if my car didn't come with it, the provisions would still be there in the harness...

 

Do you have the G/W wire at connector FDR-01?

 

Is that the plug between the front harness and the door harness? If so, I tried unplugging both sides independently to see if the short to ground went away, and it did not.

I just verified the schematic, then went out there with a flashlight to make sure my memory was correct, and there is not a green/white wire at FD01. At least I think... It's hard to tell which is FDR01 and FDR02...

 

The G/W wire turns on the small bulbs by placing a ground signal on this wire thus the question remains is the ground coming from the CPU or the wiring harness. If it's from the CPU then it's probably not an issue.

 

With my multimeter in the continuity test setting, if I put one probe on the G/W wire and connect the other to ground it beeps loud and proud. The way I narrowed it down to this wire was by removing the CPU board from the box, and individually connecting each terminal until it started squawking. Then I verified that that wire went straight to ground and started trying to figure out where to look for the short*. With most of the things it's supposed to do cryptic/not on my car, it's proving a bit more difficult.

Based on what you just said, if the bulbs it's supposed to be lighting are getting power from elsewhere and the CPU switches them to ground, they're coming in pre-grounded and it sounds like where the CPU should be grounding through its actual ground, it's trying to ground through the G/W wire.

Where/what are all these bulbs? I don't have the majority of them regardless, so which of them would an '86 have provisions for in the harness?

EDIT: *Though it occurs to me that it must also be getting power for it to make the CPU squawk.

 

It's been a pretty intense few weeks, but I finally found some time to try to finish this. I'm hoping that by sorting out my ECU issues, maybe my engine issues (which appear to be intermittent and electrical in nature) resolve themselves.

I've spent the morning with a multimeter probing the main CPU board that I resoldered a while back, and then following things up with the associated plug. When I was last messing with it, it seemed that the Green/white wire was the source of my frustration. I poked and prodded like a prom date trying to figure out what the issue could be and couldn't track anything down that was remotely out. I consulted the schematics again, and started looking at the various wires that are associated, and discovered that the plain blue wire (immediately adjacent to the black ground wire) may also be partly culpable. I could go into great detail as to how I came to this conclusion, but at present it doesn't beep with the blue wire out of the plug.

According to the schematic, this blue wire goes to the theft deterrent control unit (which I don't have) and the ignition key reminder switch. Now from previous fiddlings, I know that the CPU will beep with the doors open and that that has everything to do with the key switch. I thought it was the doors only and didn't realize there was any association with the key, because mine simply beeps if the doors are open regardless the state of the key. Ergo, mayhap something is amiss with the key switch.

Is this the key reminder switch (cream colored plastic box roughly centered in the frame)?


If so, it's looking like a promising candidate for the source of my frustration (at least regarding the beeping). I pulled the other plastic part off the ignition barrel, and that appears to be nothing more than the switch itself, so this is about the only other option. A fact contributing to that guess is that the wires leading to it were spliced (extremely poorly), and disconnecting one of them (and reconnecting the blue wire at the CPU) results in no beeping (door or extra chirp). The fact that neither of the wires is blue though is directly counter to the schematic... What's the deal?


From the switch, the wires appear to go to this plug before disappearing into the harness. Any ideas what the other two wires are for?

 

I've confirmed the plug and wire colors. The blue wire goes to the plug I pictured and I found the security system harness plug and found it there as well. The wires just change color at that plug. Cool. The other two go to the E and 7(?) wires on the ignition switch (which I'll figure out here in a second). It seems like leaving the (completely unnecessary) key reminder switch out of the loop won't hurt anything. Unfortunately, it doesn't seem like it could be the root of my power loss issues... Unless that short was causing issues with some other component related to the cpu that could somehow cause the issues I've been experiencing...