spddm0n

Ok, interesting...next question....where in the dash is the A/T Oil Temp Light? I've never seen it and I shined a light into the instrument cluster to illuminate each of the indicators while it was powered off. I don't know where in the display it would be. Any chance you could find the owner’s manual too? It might have a page that shows all the different lights in the dash in those little owner’s manuals (as apposed to the service manuals).

I'll update my previous post and add what each of the 5 pins from the control box goes to. Another interesting thing I found, is that I didn't look close enough the first time, but Toyodiy.com shows that Toyota part number actually has two different devices associated with it, denoted as NO.1 and NO.2. This little black box is probably NO.2, as indicated by the smaller purchase price (new at that time). The NO.1 is probably actually the ECT ECU itself (higher purchase price).

I'm hoping the transmission behavior I'm having is related to this box being bad. I need to find a used one somewhere (doubt I'll find any pick and pull junkyards around here with any of these trucks) and see if I can somehow find those little bulbs. Any ideas how to find those little replacement bulbs? I'm not sure how to search for a part number on something like that.

samwell121

I replaced the ECT ECU on mine and it behaved the same. Is your shift linkage sloppy as hell like mine?

samwell121

the A/T Oil temp light is bottom left side for me, not sure where on yours, Just know it's part of the A340 family

spddm0n

Interesting...yeah, that's why I'd like to test this stuff. I'm thinking about just purchasing the FSM from Techinfo Toyota. I'm not sure if they publish the testing procedures on those devices in the "Standard" subscription ($15 for 2 days). You might have to subscribe to the professional service ($55).

Ok, what year is your truck? the 87-88 DLX model (very basic - no tach), doesn't seem to show it. Actually, I'll have to go back and look. Now I think about it, I was looking for the O/D light, not the A/T OIL TEMP. The O/D light is in the center dash, near the ash tray.

spddm0n

Bummer. Turns out the Toyota Techinfo may only have 1990 and later model information.

I'll have to call them next week if I can't find the FSM in the meantime.

I'll do this the hard way for now...head back to the shop and test each of the wires for continuity and voltage response. I'll see if I can determine if the little black box is bad.

spddm0n

My shift linkage isn't bad ( could probably use a little bit of tightening ), but I don't think it's playing a huge role. I do know that the whole plastic assembly that surrounds the shift levers is broken and loose. That made me think that the shifter was loose, but I've disassembled most of it. I haven't actually been able to remove the whole thing though, because I can't figure out how to navigate the plastic face of that assembly up past the shift lever itself. I removed the shift lever handle and have it hanging to the side, but the two wires that go to the overdrive button do not seem to be able to be disconnected from the button itself. Have you ever removed the entire shifter? How do you get the entire plastic assembly out over the handles, when there is the overdrive button?

Having said all that, I determined that my quest to chase all the wires for the A/T OIL WARN COMPUTER may be irrelevant. It may not play a role in the operation of the over-drive anyway, except to simply warn the ECT ECU if the A/T Oil Temp is too high, but then that doesn't make sense either since the A/T Oil Temp sensor talks directly to the ECT ECU anyway. ??

I was thinking that since I found the A/T oil temp computer in the same general area that I expected to find the overdrive relay, and the plastic case says O/D, that it was important in that system. Since the wiring diagrams do not show any kind of overdrive relay for vehicles with the V6 engine, I assumed that this little device was taking over that same role. I don't know that to be true now.

I did manage to break the overdrive indicator light though. :-) At least I don't have to just find bulbs now, I need the whole light. :-)

i'll go back to the drawing board to try to figure out what is going on with this transmission

spddm0n

Do you know how to describe the process for checking for Codes from the transmission? I can rig up a small lightbulb to the broken overdrive light, so I can actually get a response. I haven't been able to figure out where the correct diagnostic port is for the jumper for the transmission. Some of the factory service manual's say there is a special port for this, and others say that you use the same diagnostic port for checking the codes in the EFI (main) computer.

Also, where is the EFI computer (TCCS) in these trucks physically located?

samwell121

EFI Comp is ECU in passenger kickboard, ECT Is under front of shifter. I have read several times Tranny codes go at same time as ECU codes..

samwell121

85, simple dash no tach, OD light in the ash tray PWR and NORM on the dash

spddm0n

Ah, cool. Thanks. I also just found a page in the '93 FSM showing that computer in the passenger-side kick panel. Thanks!

I also see that the process described to read codes from the transmission in there too. I was confused because the images for the diagnostic port didn't look the same as the port I have. Turns out, the image is just "upside-down" in the '93 FSM. Ugh.

I also found some new things last night on my new truck...weird.

I was worried that the truck may have originally been a 5-speed, converted over to auto. I found part of the clutch pedal assembly installed under the dash in the feet area of the driver side. I went on to find, what I can only describe as a aftermarket cruise control electronic box. I don't know if there was some relationship between Toyota and some aftermarket company making a cruise control setup that could be installed on vehicles without cruise control, or if this is a sloppy Toyota product, but it's certainly suspect. The cruise control lever that is on the steering column almost looks factory. That part is well made, but the electronic box is not factory and was tied up under the dash with a zip tie.

I noticed that the cable that connects the cruise control actuator to the throttle valve is broken off (not operating), so I think I'm just going to remove the whole mess.

This is when I identified another cable! It's the transmission kick down cable. That could also have something to do with my transmission kicking down two gears when it down shifts. Hmmm...more evidence.

I found the O/D light bulbs at Toyota. $10.00 each! Ouch! I need two now too. The second one just burned out. I also found the indicator lamp in a special Toyota salve yard in Denver. Wow, I need a parts truck. This stuff is adding up!!!

Hopefully, with the O/D light working I can check the transmission codes and find the solution to my truck being stuck in overdrive. I suppose I should probably started a new thread for this.