habanero

Trying to get my 96 4runner, 3.4, california emmisions, manual, 4x4 truck state inspected but my OBD II is not connecting to the state's computer.

There is power at the ECU and power to the OBD II connector. I have power at some of the pins but I don't know if this is good or bad or both.

Any help would sure be appreciated.

MTL_4runner

You might try getting a simple $99 OBD II reader at the auto store and see if it can communicate or not. If not, then you'll definately need to do some diagnosis to get that up and running again.

habanero

The state has tried 4 different readers 8 times....and we've tried one ourselves, but no luck.

I guess I need to know what power I need to see where when I test the pins?

profuse007

http://www.mymp3car.com/MP3Car/obdII%20pinout.html

MTL_4runner

Ok, time to get knee deep in wiring diagrams, fun, fun, fun!

The OBD-II specification provides for a standarized hardware interface—the female 16-pin (2x8) J1962 connector. There are 5 different protocols which are used on all OBD II equipped vehicles. From those 16 pins there are some common ones between protocols and some are not but this should help.

Now Toyota started using J1850 VPW in 96-97 (due to their ties to GM at that time) and then switched to ISO9141 in 1998 and later vehicles so you'll need to check the correct lines for your vehicle for any power/data signals. On my 96, the OBD protocol is VPW.


SAE J1850 VPW (Variable Pulse Width) Protocol Pins

J1850 VPW uses pins 2, 4, 5, and 16. Most American cars use J1850 VPW (as well as early Toyotas).

Pin #, Description
2 - Data (on my 96 the wire is White, goes to ECU connector)
4 - Chassis Ground (on my 96 the wire is Brown, check to ground)
5 - Data Ground (on my 96 the wire is White/Black, check to ground)
16 - Power (on my 96 the wire is Violet and is fused, 10 Amp)


ISO 9141-2 Protocol Pins

ISO 9141-2 uses pins 4, 5, 7, 15 and 16. This is the most common type for non-US vehicles, especially Japanese models.

Pin #, Description
4 - Chassis Ground
5 - Data Ground
7 - Data
15 - Data (this pin is optional and may not be present)
16 - Power

Note that pins 4 (battery ground), 5 (signal ground) and 16 (battery positive) are present in the same location on all OBD II protocol configurations. My suggestion would be to do a continuity check from the connector all the way back to the ECU connector (white wire) using a DMM. If you find any broken (non continuous lines) you found your issue. Then check the connector grounds (continuous to ground) and the battery positive (12V+) contact. Finally if all checks out you may need to bring to a shop with a scope to see the data line signal. It may take a bit of work to track it all down but it is definately solveable. Also pay careful attention to the connector itself (damaged/loose connector pins, cracked plastic, etc). This ought to get you going in the right direction anyway.

OBD II connector pin locations:

habanero

Thanks!!

Had a friend scan with his Nemesys....and it scanned just fine, no problem. We tried it several times over a couple of hours and it worked each time so I ran it back over to the state's facility...wouldn't connect again.

Eesh! I am one frustrated person at this point.

JamesD

The only 4 pins on the OBD 2 connector is 2,4,5 and 16.

2 is White and that is the serial data line
4 is White/Black is ground
5 is Brown/Red and that is ground
16 is Violet and that is fused 7.5 amp 12 volts

Check number 4 for ground and get back with me.

James

MTL_4runner

It is a good sign that at least you can read it at all with any scanner. I have only ever seen one OBD II that gave me trouble with reading it (turned out to be an issue with the connector), otherwise they rarely have a problem. It sounds like the issue is likely at the connector itself (ie pins on the OBD cable aren't making contact when inserted.....pin size may vary so one cable/scanner might work while another might not). Definately have a look at the connector and see if you can spot anything (loose wires, cracked connector, terminals too wide.....since there is a male pin on the cable that needs to make contact when inserted, etc).

habanero

PROBLEM SOLVED!!!

Thanks everybody, pin 5, the signal ground, was open. A little hoodoo wiring and voila! Passed!

Turns out some readers don't need this to be grounded, but the state's computer does.

The information given was a big help.

I suppose now I should find where the break is...

Ryan31783

I need a little help as well... same problem, my computer isnt talking to the OBDii tester, it is in a 90 with a 96 tacoma engine, harness, and computer. the first go-around I wired it all correctly as far as I can see, I have bent the pins so that they will have full contact with the connectors. I am using pins 2, 4, 5, and 16

"pin 2" runs to pin 19E on the ECU, with shielding running all the way from the OBD connector til about 3" away from the ECU (would that uninsulated 3" matter?) the shielding splices into a wire that was 22IK2 on the Taco (goes to drivers side intake manifold ground)

pin 4 runs to the circuit open relay ground (i may have just grounded it, I need to go out and double check, but it shouldn't matter ...maybe it does)

pin 5 is also grounded to the drivers side intake manifold ground

pin 16 goes to some power source ...does it matter where it goes? I am under the assumption that as long as it is +12 it should work.

the truck runs awesome, I don't have a 2nd O2 sensor on it, but I built a fooler, maybe it isn't working? anyway I would just like to be able to read codes to see what it is.

Ryan31783

electrical wiring diagram for 96 TACO

hrt4me

thanks for the helpful info!

pc007chan

I know it a old thread. but I run into same issue. OBD commuite with my scanner but fail at station.
How did you ground the pin 5? spice a wire and ground it?

habanero

After finding pin 5 was open we ran a small bit of wire from pin 4 chassis ground to pin 5 data ground at the back of the connector to complete a ground. Still works great.