401-J10

I guess this is getting to be a pretty old swap, but I hope someone can help. I've put a 98 (I think) 4runner 3.4 engine and automatic harness into a 90 pickup that was a 3.0 M/T. The ECU is from a 98 4runner V6, M/T, 4WD. Most everything is done at this point, and the engine turns over fine, but it won't fire. I'm questioning the ECU the most right now. I've verified that its getting 12v+ constant and switched, and that its getting ground to the 4 pins its supposed to. While the CEL does come on when the ignition switch is on, I've tried 2 different OBD scan tools and neither will communicate with the ECU. I don't think I'm getting spark either. I've tried searching here and through the service manual and I haven't found a way of testing the ECU besides swapping it for another one.

So, while I do realize that there could be an issue with my wiring, my thinking is that if the ECU is getting power (as mentioned above) it should communicate something to the scan tool. Out of curiosity, I checked the signal wire at the OBDII port with a multimeter and got 12V+. I thought since this wire was supposed to send a signal from the ECU, that I shouldn't be getting stable DC current like that?

I think I can get an automatic ECU for fairly cheap locally, so I'm thinking about giving that a try. If I remember correctly, a M/T will run with an automatic ECU, it'll just throw codes? Any ideas or suggestions would be greatly appreciated.

Kolton5543

Are you sure you have all of the power to all the wires that need it. The ecu needs at least two. There might be three but I might be wrong. Also make sure that all of the coils and sensors have power too. They are fed power separate from the ecu. Also the fuel pump relay was controlled by the AFM on the 3.0. With the 3.4 it needs to be wired to operate with the ecu. An a/t ecu will run as a manual. Like you said it will set codes but it will run just fine. That's how mine is set up at the moment. I'll check my diagrams tomorrow and let you know for sure what all needs to be connected to what in order to start.

Also, how do you have it wired? Did you repin connectors? Make a PNP harness, twist and tape, or is things booty fabbed with switches everywhere?

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401-J10

Thanks for the reply. The Ecu is getting power at the batt and b+ terminals, well unless somehow it's not making it through the ecu connector. And I haven't checked all the other components, but the coils and igniter are getting power. And I did wire the COR to the fc terminal of the ecu. And I made a PNP harness, although I am using twist connectors temporarily so if I had to change something it would be easier. I didn't repin the connectors since the 98 uses the same connectors for auto and manuals. But I'm sure it wouldn't hurt to verify that the pinouts are all the same. Any other ideas?

Kolton5543

Sorry for getting back a bit late. I've been real busy lately. I looked at some of my diagrams and it looks like the pcm has power correctly. If you have power to your coils and injectors then you should be good there. Make sure to check for ground at everything too.

I think you need to start from the basics. Pull some plug wires and make sure you have spark while cranking. If not then we can go from there. If so then spray a little carb cleaner in the intake and see if it fires. If so then you got a fueling problem.

As for the scan tool issue I'm not too sure what to think about that. There certainly shouldn't be 12v on the data pin. Are you sure it's wired correctly? There should be three wires. One 12v, one ground and one data. I don't remember for sure exactly which pins are supposed to be what. I'll have to check my references again.

When I get the chance I'll attach a copy of my wiring tables. I put an engine from a 98 auto 2wd into a 94 manual 4x4 so it should be pretty similar. It worked perfect for me so if you double check your wiring with mine it should be pretty close.
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401-J10

Thanks for your replies. I went back and looked into the wiring some more, and I discovered what is most likely causing all my issues. When I bought the engine and harness, I was told they were a '98, and the ecu plugs worked with the ECU I had from a '98, so I assumed plugs E9, E10, and E11 were good. I'm sure you know this was a mistake. While a lot of the wires are right for a 98 ecu, some are wrong. So after going back on TIS, it looks like the harness is a 97.

So I've kind of been on the fence about whether to repin the connectors, or find another harness. But I think I'm gonna try to save some money for once and repin the connectors. I don't think it'll actually be that many wires that I have to change. I am still sort of wondering about the OBD port issue though, because the ecu was still getting power at the right terminals, and the OBD plug was wired right. But I guess it's hard to say what else was going on with that messed up wiring. I guess I'm just wondering if the ECU is fried at this point.

Kolton5543

Its easy to just repin the wires. Just do them one at at a time. Don't get carried away with it. Trying to find another 98 auto harness can take some time and can cost quite a bit extra.

401-J10

I ended up repinning the connectors, and redid my conversion harness. And I'm very happy to report that I got it running!
I used an automatic ECU I had, so I'm still not sure if the manual ECU is bad or not but hopefully I can try it tomorrow. I just want to say that I really appreciate everybody on this forum cause I definitely wouldn't have tried this without everything I learned on here.