hi i have a 98 t100 and ive been trying to pull the error codes from the ecu. but when i hok up the reader it will not connect. i dont have a manual right now, and i can understand why it will work on every other vehicle i pull codes on, but not mine. i have pulled codes on other toyotas so i think its working fine. and it has never failed on other vehicels. <img src="/forums/images/graemlins/confused.gif" alt="" />
is there a circuit that needs to be closed to connect the circuit. can someone send me a pic of the wiring diagram that has this portion. i cant find my service manual now that i need it.
my check engine light comes on when in overdrive and i can feel the engine *sputtering* a little on acceleration. i have replaced one of the coils so far a few months ago. and its acting like the same problem.
thanks bill

No special tricks are needed. You should be reading when you hook up, running or not, as long as the key is on.

I have found the connection problematic for driving with the scanner hooked up. It will very easily lose the connection momentarily.

If it's been a long time since anything has been connected to the OBD-II port it's possibly dirty enough to prevent a good connection.

well ive had the truck for 5 years, and i have tried to have the local auto parts store try to read codes and they get the same no connection....
ill look at the connections but i think they are clean.
i thought maybe there was a switch that needed to be turned on. on older importd you have to put a jumper in to read the check engine codes (flashing).

all the wires look like they are ok in the plug. can i do a connection check or a voltage check on the wires to see if they are connected. do these wires go strait to the ecu or do they go to the fuse box or somewhere else first.
thanks bill

The battery connection goes to the fuse box. The two wires for the data signals go straight to the ECU.

Sounds like you're going to need a factory manual to do some deeper troubleshooting. You'll need to check wire continuity from the OBDII connector to the pins on the ECU. Maybe some wires got cut during a botched stereo or alarm install?

If the wires are OK, you could have a bad ECU.

There were three OBDII interface electrical standards in use for your era vehicle.

Those are the VPW (Variable Pulse Width Modulation) used primarily on General Motors vehicles, PWM (Pulse Width Modulation) used by Ford and, the International Standard or ISO 9141 used by the Chrysler motor vehicles, European and Asian manufacturers, including later model Toyotas.

Does your OBDII scanner you are trying to use support, and is it set to the ISO 9141 standard, used by your 98 T100?

im not sure if the scanner/reader is set to the ISO 9141 standard. ill check it later tonight, however i went to 2 different autozones stores and it would not work at either one of thoes locations.
the plug itself looks just like the one that is in my toyota sienna and chevy equinox, also pulled the the codes on my sisters olds 1998 minivan with no problem.
i think it should read the codes on my truck, but ill check with the scanner manual again.

thanks bill

I have a 97. It does NOT speak ISO9141. It speaks PWM - the Ford standard. This is very peculiar I think for Toyota.

You can tell by looking at the contacts installed in the OBD connector.

FWIW since our trucks are a joint collaboration it seems with GM, since they have GM parts I would expect it to be read by anything that will read a GM.

I just did mine the other day and it worked fine, your sure your doing it from the hookup under the dash right? Cause that thing under the hood it seems is only for special scanners (got one at my shop) or a toyota specific scanner tool.

Yea i use the under dash hookup. ill try to look tomorrow when it warms up a little. maybe one of the wires is pushing out the back of the plug...

thanks bill

can someone tell me how many wires should be in the plug