TEB OBD-1 Tool

[ThreeEyedBandit]

Continuation from here

9/22/26 - And current status of data on at post #13

Not sure what to call this, so here it is.

If there was a standalone device, what all do people want? I know coolant temps. I have been farting around and have a dedicated fuel usage screen along with basic diagnostics and user settable alarms.

Also a decent web ui which will allow decoding check engine codes along with up to four analog voltage measurement channels coming next.

Any wish list items? Going to work on PCB design this week and hopefully order a batch before a trip the following week.

Also, I'm sure this isn't the right place to post this. Will start something as I work through the UI.

Bringing questions from the previous thread here, give me a moment to catch up.

 

[ThreeEyedBandit]

It's less of a real-time use, but a OBD-1 CEL code reader was what originally caused me to click on this thread. And I really like where you're going with coolant temp and alarms that can be set for any key values that are out of range. AFR would be a nice option for the turbo crowd. And for the fuel screen, distance to empty would be a nice modern convenience if you're able to calculate it.

@cts This should be easy to add. Will see how a second page looks to split up the data, but might cause a bigger display to be needed. Great idea!

 

[ThreeEyedBandit]

nice work! there is another box under the dash? does it have like 30 wires going to it? I'm guessing its not possible to get fuel trim data. if not o2 voltage data would be useful. Would be kinda nice to see the idle switch on the TPS. I don't own a gas 80 but might be interested in having it just as a scan tool if its quick to connect inline with the ECU.

@TheBussman
Nope, no extra box. Display and processor along with basic daughterboard is in my hand.
Only eight wires going through the firewall, four are unused but have plans as explained in a few. Whole cable is about 1/4" diameter.

The four extra wires are for monitoring 0-15v. DLC has both O2 sensors voltage and fuel trim available. All four are untested, but these are what I am planning on them being used for. Can be used for any available voltage in the DLC up to 15v.

The last bit of data am finally decoding from the ECU is;
Cold Start
Warm Up
Start Switch
IDL switch <---
A/C Switch
Neutral Switch
CEL status.

All of these are untested, but hope to get to them tomorrow after work. They will require another page on the device, which is becoming more apparent that a larger display might be in store for the near future.

The hardest/dumbest part is connecting it to the DLC. Currently I have bare male pins the you insert into the respective location, need four at a minimum to read live data. I am hoping to find a decent fitting connector, but the couple I have bought are so bad they wont fit the factory end..

 

[ThreeEyedBandit]

Transmission oil temperature. This is the only (useful) parameter, available to all 80 series ('93–'97), not exposed by OBDI/II.

There's a sensor in the cooler loop, but it's only accessible to the TCU circuit (or TCU in the '93–'94 models), for some (PITA) reason.

@Malleus Where are you seeing this? I looked through my 93 EWD and do not see anything in the ECT or or SFI section showing a temperature sensor, or any code for one in either.

Screen shot of the EWD or any data you have would be greatly appreciated!

Just an over temp switch for the light on the dash. If we could find a easy point to tap into the sensor we could use one of the extra inputs, do some math and read live trans temps. That would be super nice!

 

[Malleus]

It's in the cooler loop, on the front of the transmission, on the cooler line connection to the case. It does more than illuminate a light on the dash; it is integral to the engine shutdown for overtemperature.

The transmission harness connection is on the sensor, on both the A442F and A343F. If you look at the transmission, you can't miss it.

 

[TheBussman]

@TheBussman
Nope, no extra box. Display and processor along with basic daughterboard is in my hand.
Only eight wires going through the firewall, four are unused but have plans as explained in a few. Whole cable is about 1/4" diameter.

The four extra wires are for monitoring 0-15v. DLC has both O2 sensors voltage and fuel trim available. All four are untested, but these are what I am planning on them being used for. Can be used for any available voltage in the DLC up to 15v.

The last bit of data am finally decoding from the ECU is;
Cold Start
Warm Up
Start Switch
IDL switch <---
A/C Switch
Neutral Switch
CEL status.

All of these are untested, but hope to get to them tomorrow after work. They will require another page on the device, which is becoming more apparent that a larger display might be in store for the near future.

The hardest/dumbest part is connecting it to the DLC. Currently I have bare male pins the you insert into the respective location, need four at a minimum to read live data. I am hoping to find a decent fitting connector, but the couple I have bought are so bad they wont fit the factory end..

wow impressive you can read all that with just 6? wires. i was thinking of something like this:

i actually used these back in the day, unplug the ecu and plug this machine inbetween it and the rest of the engine. the factory toyota tool that plugs into the obd1 connector under the hood didnt even have that much info on it.

 

[TheBussman]

It's in the cooler loop, on the front of the transmission, on the cooler line connection to the case. It does more than illuminate a light on the dash; it is integral to the engine shutdown for overtemperature.

The transmission harness connection is on the sensor, on both the A442F and A343F. If you look at the transmission, you can't miss it.

it may do more then just turn the light on but I was pretty sure it was just a switch and not a sensor.

 

[Malleus]

What's the difference between a switch and a sensor? It's the signal that's being used, not the source.

 

[ThreeEyedBandit]

View attachment 4217226
What's the difference between a switch and a sensor? It's the signal that's being used, not the source.

Are you sure that is used on an OBD1 Cruiser? I can only find it referenced for 1995-1998 vehicles, and in the 1996 FSM wiring diagrams which does go to the ECM. Nothing in my 93 or 94 manual shows that sensor.

I know the one on the union of the A442F, it has a round single wire connector which matches the early wiring diagram going to the gauge cluster light.

I really hope I am somehow missing this in the early trucks, but can't find any information in my FSM's about the A/T temp sensor going to the ECM or TCM.

 

[ThreeEyedBandit]

wow impressive you can read all that with just 6? wires. i was thinking of something like this: View attachment 4217217 i actually used these back in the day, unplug the ecu and plug this machine inbetween it and the rest of the engine. the factory toyota tool that plugs into the obd1 connector under the hood didnt even have that much info on it.

It's funny, I remember dragging my old OTC 4000 around to friends houses with all the adapters and cartridges. Very glad it was as portable as it was!

I am pulling reading all the serial data from the ECU, which the Toyota scanner should have also. The 02 sensor and trim values are on separate pins in the DLC, and I am calculating fuel mileage stuff from injector pulse and speed. I'll add a list of all the info and where it comes from in a few.

 

[Malleus]

Are you sure that is used on an OBD1 Cruiser? I can only find it referenced for 1995-1998 vehicles, and in the 1996 FSM wiring diagrams which does go to the ECM. Nothing in my 93 or 94 manual shows that sensor.

I know the one on the union of the A442F, it has a round single wire connector which matches the early wiring diagram going to the gauge cluster light.

View attachment 4217327View attachment 4217328

I really hope I am somehow missing this in the early trucks, but can't find any information in my FSM's about the A/T temp sensor going to the ECM or TCM.

That's the sensor. It's the same on the A343F; and it's tied into the TCU circuit, whether the EWD says so or not.

 

[ThreeEyedBandit]

Here

That's the sensor.

Correct, and it is not on my A442F. Mine is a round single pin connector, no sensor like that on my A442F's.

P/N shows for a 95-98. I only have A442F/OBD1 trucks to test.

 

[ThreeEyedBandit]

Here is where the project is at as far as data being displayed, and the source. All are displayed on the web UI, ones marked with * are on display.

VF1~Serial Data from ECM, E1-TE2
Live data:
*Injector pulse width
*Ignition Timing(need to confirm/correct)
*IAC Step position
*RPM
*VAF(need to scale properly)
*Engine Coolant Temp
*TPS angle(need to confirm)
*Speed

Flagged values:
Cold Start
Warm Up
Starter Switch
Idle Switch(closed)
A/C
Neutral
CEL status

Calculated from above is;
*Current mileage
*Average Mileage
*Fuel used <- Moving to diagnostics page and adding Distance to Empty

Useful analog output available at the DLC;
Fuel pump voltage
First O2 voltage
Second O2 voltage
First O2 compensation
Second O2 compensation

These can be read from the four extra analog inputs, and visible/short graph from web UI.

One caveat, the first O2 sensor compensation is on the same pin as the serial data stream. This will not allow live data and reading this value at the same time.

Currently working on adding a CEL decode to the webUI, should be simple and pretty slick.

 

[Malleus]

What I posted above was for the 3rd generation 80s; it was the most handy. This is the 2nd generation 80 sensor. The fact that it's NLA, means you have to use the other one; they're interchangeable.

 

[Malleus]

Regardless of either sensor's intended use, they both are positioned in the cooling loop immediately adjacent to the case and are able to provide a direct temperature indication for the transmission fluid in the case.

 

[ThreeEyedBandit]

If that's the case can you show on a A442F truck where the temp sensor is wired to the ecm or tcm? No FSM that I have confirms this.

I have confirmed on my 94 that it's a single wire 'sensor' that is wired directly to the gauge cluster and no continuity to any pin on the tcm or ecm

 

[TheBussman]

View attachment 4217226
What's the difference between a switch and a sensor? It's the signal that's being used, not the source.

Switch opens and closes the circuit at a certain temperature I think its around 300 degrees on this switch. a sensor changes resistance with temperature. 90-94 defiantly does have this switch, its in the interment cluster section of the wiring diagram. I've drilled and tapped many of the unions and installed the extra short sensor from auto meter. works well.

 

[ThreeEyedBandit]

Either way getting we are getting off track. If we can get the data from the computer it would be great to easily be able to monitor the transmission temps. It'll be something for later self to figure out

 

[Malleus]

Tapping into the SENSOR circuit would be easier.

 

[ThreeEyedBandit]

Yup, that's my plan once I find an A442F that has a analog SENSOR that isn't a thermal switch like in both of my transmissions.