Unable to connect to ECU...

[Chewy]

Hey fellas,
I've been on the forum for a while but haven't really posted that much. I just recently completed my swap, putting a 1UZ from a 97' SC400 into my '98 4Runner. I had Doc over at Phoenix Tuning do the harness conversion for me.

Well, the big problem I'm facing right now is not being able to connect to the ECU. I was on the phone for a few hours yesterday with Doc; we tried testing different wires, connections, etc with no luck.

When you plug in an OBDII reader into the data port under the dash, it gets +12V power. The problem is when you try to link to the ECU; an error comes back saying "unable to establish link" or "link error", etc. depending on which reader you use (I've tried several).

The data port has four wires; the "data" wire, +12V power, and two grounds. I've checked the continuity of the data wire from the port to the 40-pin ECU connector and it's good. I also made sure the wire wasn't grounding out somewhere along the way. So as far as I can tell, the data is able to "physically" pass from the port to the ECU and vice versa. I also checked the OBD fuse and tested the two ground wires and they're good.

So at this point I'm out of ideas. Doc thinks it might be a loose ground somewhere or an outside chance that it may be the ECU itself. I looked everywhere and all the grounds are clean and secure. Short of buying a new ECU, do you guys have any suggestions?

Oh yeah, the motor runs but it sounds like it's missing. I've checked some simple things like making sure the plugs were wired correctly, wires grounded, etc. But before I start tearing the motor back apart, I'd like to be able to connect to the ECU and have IT tell me what's wrong! Any ideas?

 

[Chewy]

OBD-II connection issues

After troubleshooting just about everything, I decided to try a new computer. I hooked it up and still have the same problem of not being able to connect to the ECU. :34: So now I'm officially out of ideas.

The way I understood it, the 12V+ wire and one of the grounds were used to power the scanner, and the signal (SDL) wire and other ground were used to communicate with the ECU. Is there something else? What is the "process" that enables a scan tool to connect to the ECU? Are there any specific signals or inputs that need to be present in order for the scanner to connect (other than the SDL wire)??

 

[Udlman]

Have you cleaned all the crap out of the holes in the socket?. On my half cut my cabin diag port (big round socket under steering wheel) was full of grease and it made it hard to trace the wires.

 

[Chewy]

Yeah, I've done all of that already...cleaned the contacts, re-did the chasis/block grounds, checked continuity, etc.

It just seems like I'm missing something; like there should be another wire or connection that needs to be made somewhere...

 

[sideshow]

have u tried hooking up the older dlc3 plug i think
obd2 on tooyotas has different wires to that of a gm or ford
ive don e many aussie toyota late model desiels and never have had any probs
i would get the doc to go thru his diags and see if the 97 actually had an obdii port

as most of the later 1uzs ive done dont actually have one
till maybe 2000

 

[Chewy]

Success!! I'm finally able to connect to the ECU!!!
I was on the phone with Doc Tweak yesterday and asked him about the pin-outs on the OBD-II connector. Looking at the 4Runner's port, it had pins at 16, 4, 5, and 7. This made sense with what I'd read; most Asian vehicles use this ISO 9141 protocol.

Well we figured this was used with all Toyota/Lexus vehicles until we looked closely at the wiring diagram for a '97 SC400. Turns out the signal wire is on pin 2, not 7!! I swapped the pins and just like that I was able to connect to the ECU and pull codes! Now I'm off to troubleshoot two misfires. :ugh1:
Thanks for the help guys... :bigok: