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My 1988 Pickup doesn’t have a square diagnostics box (on the passenger side next to fuse box) that seems present on all 1988 trucks. (see photo)
It also doesn’t seem to have the round diagnostic plug(s) on the driver’s side that seem to be present on pre-88 trucks. (see photo)
Therefore I’m not sure how to complete procedures such as setting ignition timing, checking ECU codes, etc. as per the procedures in the FSM (because they all require the diagnostic port).
I’D LIKE TO HEAR YOUR THOUGHTS ABOUT…
Is there another way to properly set the ignition timing without a diagnostic box (and other test procedures for that matter)? Only idea I’ve discovered in my research is grounding terminal "T" at the ECU (read more about this idea on this thread).
Should I try to install a diagnostic box into my truck? For example, I’ve considered finding a square diagnostic box, an ’88 harness, and swapping it all in. But then it seems I’d have to swap injectors and possibly other items that might not make that a viable option. Any other ideas?
Aside from not being able to properly set the timing, should I be concerned about other issues due to the absence of a diagnostic box?
So any help would be greatly appreciated. Bonus, if you’re in the Albuquerque area & you know of a good mechanic for these trucks, definitely let me know!
My understanding is that this isn't a vacuum advance distributor. I'm thinking the two hoses from that unclear photo you saw go to the power steering. Can you let me know what you think based on this photo, which is hopefully clearer? I'm happy to take more if needed.
And here's some drive / passenger engine bay shots for easier reference...
I would guess you looked for the port just hanging loose in the harness??
Are there any plugs on the left inner fender by the coil that don`t appear to go any place??
Yeah, I've looked all through the engine bay and I can't find any connector or wire that isn't already hooked up. When I pulled the motor I had documented all the connections and everything went back together as it was before during the reinstall. It was only after reinstalling the motor when I tried to follow the timing procedure did I discover the need for a diagnostic port.
Now refresh me has this engine ever run since you bought the truck or did the truck come in a big box in pieces ??
The truck was like this when I bought it and it did run / was driveable. It leaked like crazy and I wanted to learn about it so I pulled the engine and rebuilt it. It was throughout this process, as I was learning about the truck, was ordering parts, when I discover it wasn't the original engine, diagnostic box was missing, etc. It's been running okay since the rebuild despite not being able to properly follow the timing procedure.
Now that manifold is of earlier vintage for sure ??
My guess is that's it's pre-88 but I really don't know. When I bought the truck, it had an O2 sensor in the manifold that was not plugged in. I discovered this as I was documenting the wiring in order to pull the motor. During the rebuild I blocked off the O2 spot in the manifold. The truck also has an O2 sensor right before the cat that does appear to be connected.
Who can say what was done manifold engine harness and engine from all different years??
I've read your other threads and from my personal experience it looks like that engine and harness or at least part of it is from and earlier 85-86 truck or possible 85 Celica. In the other thread you mention you have no knock sensor but do you have the plug for one? Also the o2 sensor on 88 trucks are mounted before the converter and have four wire while the 85-87 are mounted in the manifold and have 1 wire. That engine also has a temp sensor in the thermostat housing which was gone in 88. The (black box) is in the engine harness that gets pulled when you pull an 88 motor but on the 85-86 models with the round connector it stays in the engine compartment because its on the driver side fender. Best fix would be to try and find an 88 harness that way everything would work right. Or you can use an earlier ECU but you would have to run some wires to make things work. Without diagnostic box the only way to set your timing and read codes is jump terminal T at the computer to ground. My opinion would be to get a harness with a diagnostic box and if your worried about the injectors just cut and solder the plugs from your harness to the new harness, install a knock sensor and hope the previous owner didn't mess with the other wiring in the truck. What part number ECU are you using?
Hey 854x4, thanks for jumping in on this conversation!
Here are some responses...
In the other thread you mention you have no knock sensor but do you have the plug for one?
It does have a knock sensor. That earlier thread was very early on in this process and I was struggling with all the pieces. I'm still not an expert, but I'm confident I was mistaken and it does have a knock sensor. My bad.
Also the o2 sensor on 88 trucks are mounted before the converter and have four wire while the 85-87 are mounted in the manifold and have 1 wire.
Yeah, my truck has an o2 sensor before that cat and it's a 4-wire sensor. The wiring runs up into the cab on the driver's side. There's a connector next to the driver's seat and then it disappears into the dash near the fuse panel.
What's always bothered me about the unconnected o2 sensor that was in the manifold is that there was no connector for it in the engine bay. I would have thought that, if my harness is pre-88 donor harness, there would be a single wire for the o2 sensor laying around but I haven't found one.
The (black box) is in the engine harness that gets pulled when you pull an 88 motor but on the 85-86 models with the round connector it stays in the engine compartment because its on the driver side fender.
That is very good to know! I didn't realize the diagnostic box stayed with the harness. That makes a little more sense why my diagnostic box was deleted when previous owner swapped in a pre-88 harness.
Best fix would be to try and find an 88 harness that way everything would work right. Or you can use an earlier ECU but you would have to run some wires to make things work. Without diagnostic box the only way to set your timing and read codes is jump terminal T at the computer to ground. My opinion would be to get a harness with a diagnostic box and if your worried about the injectors just cut and solder the plugs from your harness to the new harness, install a knock sensor and hope the previous owner didn't mess with the other wiring in the truck.
Thanks for this recommendation! I was considering sourcing an 88 harness as well. Come to think of it - I wouldn't mind getting new injectors anyway (witchunter mentioned one of them was nearing end of life anyway when he cleaned them).
I may have more questions about a full harness swap later. I'm curious if there are any other '88 style connectors will need to be present (other than injectors) for the swap to happen.
Maybe I could jump terminal T at the computer to ground as a way to get the truck tuned properly while I'm looking for an 88 harness.
What part number ECU are you using?
The numbers on the ECU are kind of thrashed. The top number looks like 39661-35020 or 89661-35020. Here's a picture of it.
OK that ECU 89661-35020 comes from a 1985 22re I have the same one in my 85. If you want to run a 1988 ECU you will need part number 89661-35130 if its California emissions or 89661-35110 if its federal emissions. I would try to get the 89661-35110 federal since I don't see an EGR temp sensor or air injection on your engine. My 88 has both air injection and EGR temp sensor and I run a California computer. The reason the connector is not there for the o2 sensor in the engine bay is because the harness that the connector would be on 85-87 stays in the truck when the engine is pulled. I would try to set your timing and find out what codes your getting. For right now you could run a wire from the engine bay o2 sensor into the cab and to terminal ox on the ECU. Or you can use the o2 underneath the truck but you would have to check and make sure its hooked up right. All plugs except for the injectors should be the same between the years. Let me know if you need help.
Sounds good. The wire you need to ground is in the 1st picture middle connector and 3rd from the left, should be green with a yellow stripe. It looks like this wire just runs about six inches to another connector shown in the bottom right of the 2nd picture and would plug into your vehicle harness. Shown better in the 3rd picture. On 85-86 that wire would run from the bottom connector to the vehicle harness and then to the driver side fender where the round diagnostic plugs would be. On your 88 that wire should run from the ECU and just quit right at that bottom connector in picture 2, I don't think your vehicle harness would have this wire on the other side.
As far as the O2 sensor it has 4 wires
1- Signal wire
2- Sensor ground
3- 12V Heater
4- Heater ground
The heater ground is going to be your problem because the 88 computer grounds this wire internally. You can however ground this wire permanently, this will allow your O2 to heat up and work normally. I will check my diagrams on the o2 wiring and get back to you on the colors.
BTW the harness and computer in the pictures come from an 85-86 so it should be the same harness you have in your truck.
One more thing if you set it up so you can put your ECU into diagnostic mode and set timing, check codes and get the O2 wiring sorted out then you really wont need to find an 88 harness or computer, provided nothing else comes up. Just a thought.
Also I made a mistake in my previous post that I went back and edited the part numbers for the ECU are
89661-35130 California 1988 22RE
89661-35110 Federal 1988 22RE
Not 89661-35010 like I posted earlier that part number would be for a 85 Celica.
It sounds like someone has swapped in different years of harnesses. 88 is one year injectors only but really from 84-88 each year is different. I have seen so many changes from year to year that if you don't know what to look for you would think the 85-87 are the same. I can identify those years just by the wiring in them. 85-86 is about the closest to each other but there is a few things that separate them.
Make sure all your harnesses are 88 specific. The part number for your main harness is on a white tag just above the steering column. You will need to remove the speedometer cluster and I think you can see it with the cluster out. I forget, but there is a place you can enter your part number and it will tell what it goes to.
Even each main harness is different for the same year. From what I can tell the main harness part number changes with each option that is wired into the main harness such as standard/automatic transmission, cruise control, headlight reminder, low level fuel light, glove box light, and some other options that I cant think of right off.
Even something that should be the same such as the wiper motor, Toyota changed the plug connector and wiring colors. All 4 wires are blue but they changed the stripes on two of the four wires from year to year.
Just a couple of things to help identify which year harness
84 has an external voltage regulator
85 usually does not have a starter relay/white injectors-87, same computer as 86
86 will have starter relay/round diagnostic connector,O2 sensor in manifold,
87 has the diagnostic port on passenger side
88 has red injectors, O2 sensor by transfer case
89 has different red injectors
Those are just some quick differences, even the fuel pump/tail light harness plugs are different along with several other small things that I cant think of right off. Get all of your harnesses off of the same donor truck.
An 85 wiper motor plug is the exact same plug as the starter relay. Before I knew of the differences I connected my wiper motor to the starter relays plug. When I went to install the starter relay and could not find the plug for it, it took me a while to figure it out. Had I stayed all the same year, that would not have happened to me as Toyota does make each plug fool proof for the entire harness that is for the same truck.
I could write a book on just the differences that I am aware of and sure there are other things I am unaware of.
The wire you need to ground is in the 1st picture middle connector and 3rd from the left, should be green with a yellow stripe.
Perfect. I'm not going to be able to look at the truck for the next few days (I'm out of town) but I will have a look next week.
It looks like this wire just runs about six inches to another connector shown in the bottom right of the 2nd picture and would plug into your vehicle harness. Shown better in the 3rd picture. On 85-86 that wire would run from the bottom connector to the vehicle harness and then to the driver side fender where the round diagnostic plugs would be. On your 88 that wire should run from the ECU and just quit right at that bottom connector in picture 2, I don't think your vehicle harness would have this wire on the other side.
Ah, I'll see exactly what's up w/ that connector in picture 2 on my truck. I haven't actually investigated if the vehicle harness is still '88.
The heater ground is going to be your problem because the 88 computer grounds this wire internally. You can however ground this wire permanently, this will allow your O2 to heat up and work normally.
Awesome. That sounds like a good temp fix.
One more thing if you set it up so you can put your ECU into diagnostic mode and set timing, check codes and get the O2 wiring sorted out then you really wont need to find an 88 harness or computer, provided nothing else comes up. Just a thought.
Yeah, that's a good point. I may ultimately aim to get it all back to '88 wiring but if I can actually get the truck in diagnostic mode and the o2 sensor working, I'm happy to run it like that for a while.
Also I made a mistake in my previous post that I went back and edited the part numbers for the ECU are
12-27-2015, 09:23 PM
