TDCL, Toyota OBD1 diagnostic port reader, poor man's scanguage
 

I was searching for a pinout for the toyota diagnostic port on my 1994 geo prizm to see if I could get more than just the O2 sensor off of the connector, and I found a tool that might work. primavistalab.com/myengine/ - Translator Down at the bottem of the page is the English version.

I'll test it when I have a chance to build the cable, but it looks promising. Looking at the translated version, the software can show fuel consumption. I know a MPGuino is a better long term solution for a FCD, but this allows me to see what the ECU is seeing so I can find any issues with my car.
EDIT: I found a PDF that outlines behavior in diagnostic mode, it looks like you can setup a micro-controller real easily to read the code.
http://carina-e.ru/download/file.php?id=20531
I found what looks to be the source code for the software, or it might not be, I can't tell, but it has the same results, it looks like what I found can be re skinned for English, gallons, and miles.


EDIT:
Cartester8000 seems to work for reading the data stream. A USB to RS232 dongle off of ebay and a simple cable is all that is needed hardware wise.

OBD-1 Serial Interface - Toyota Wiki

Update: It works, I just need to work out issues with the cable to get it to read right.

Interesting find. I'll be looking out for more information as I own a 1993 LSi 1.6 w/4spd.

V0.1 of my cable was held together with wire nuts and used the sheilding as a capacitor, it didn't work very well because of interference when the engine was running. I'll need to revise the design to get it to work better, but I did get output last night and I got fuel consumption, RPM, timing advance, coolant temperature, feedback state, rich running indication, throttle position, MAP, target air fuel, knock sensor, speed, and IAC duty rate. It refreshes I think every 1.3 seconds, but when trying to find an issue, it still can be of help on our OBDI toyotas. If you have a TE2 pin, you likely have support for this on your car.
V0.2 of my cable will use a twisted pair cable and better pins to connect to the diagnostic connector with. I'll post a video next time I have enough free time to mess with this.

Are there any Updates ? :)

I'm trying to figure out why it won't work anymore.

The software is getting a signal, the ECU is sending a signal, but it isn't displaying anymore.

I'll see if I can dig up a windows XP laptop and run it on that or maybe it is the cable I soldered together that is the issue.

wow thanks for replying, im still hoping i can use this in my toyota starlet from 1991

did u make a video of the old working setup that you could show, i would love to see it

No. The setup wasn't that complex anyway, just TE2 jumped to E1, E1 connected to the serial port pin 5, VF1 on serial port pin 6, and a capacitor (1.5nF-3nF) between VF1 and E1.

OBD-1 Serial Interface - Toyota Wiki

Update: This works.

http://i.imgur.com/eXV2NAF.png

I used the cheapest USB to RS-232 dongle I could find on ebay and really short wires leading up to the RS232 dongle.

I'm still following this, so looking forward to see a good result from you

Thanks for the info, I was wondering if it would be possible to get ScanGauge data on an ODB1 vehicle somehow. (In my case, a 1991 Toyota Corolla.)

It looks like if you have a TE2 pin on the diagnostic connector, you have TDCL.
I'll do a cleaner write up when documenting Project E. Currently working on a Bachelor of science in Electrical Engineering so time is tight. I have the material, just no time to track everything down.

hi
looks like a very nice app :o
but what capacitor is needed? is there a specific one with a range of 1.5-3.3 or can u choose from either 1.5, 2.3, 3.2 etc?

and do you have a video of this thing in operation?:o

and what voltage is the capacitor supposed to be at? 12volts or something else?

You can choose. I just used a random cap that was in the capacitance range but you may want at least a 12V cap (voltage can be higher but not lower).