TOYOCOM :: UNIVERSAL MODE how to monitor fuel trim

Getting fuel trim into toyobd1

All pre-obd2 diagnosis box have the VF(1) contact pin.
Depending on the ECU and production years some can output the obd1 data stream ,some will only give the fuel trim.

following the theory found here https://people.well.com/user/mosk/Vfsignal.htm a toyocom sensor curve was written for it.

The fuel trim tells us how much the ECU believes the engine is out of tune, a near 0% is a perfect score.

Android app setup

With toyobd1 running and the bluetooth connection established with your toyocom.
Go to main menu /configuration / Display
in there check the VF1 checkbox

Go back to the main display, there you will find the new VF1 cell
in that cell you will find a button in it`s upper right corner. Press on it.
a dialog will appear for you to choose a sensor curve to use for VF1.
In there using the drop down menu select 'Toyota obd1 fuel trim'
then press the apply sensor curve button
the dialog will go away and the new senor curve will be applied on the VF1 display cell.

TOYOCOM :: UNIVERSAL MODE

WHAT IS IT DESIGNED FOR

Meant for Toyota cars before the obd1 data stream. Quite limited in comparison with the OBD1 mode and more involving but still relevant on cars with nothing at all. On older cars VF (fuel trim) can be read directly off the diagnosis box, this tells us how much the engine is out of tune, with the added installation of  the 'one wire setup' one can see the injector usage in conjunction with the fuel trim at any given RPM making for a deeper understanding of the situation, useful for engine tuning on stock ECUs or health monitoring for a daily driver.

 ENGINE ERROR CODES

Engine error codes output can be triggered with the tool, depending on the car`s wiring diagram it may lack the W wire in the diagnosis box to get the codes into the toyocom, in this sitatuation one must rely on eye reading and compare with the chart built into the error codes glossary built into the android app. On cars with complete wiring the error codes are fed into the tool and the android app.

CUSTOM INPUTS

Additionally it allows to read simultaneously custom inputs from different spaces in the diagnosis box, (VF2,TS,TT,AB) This allows to replace the SPD,RPM,INJ reading with custom sourced signals which are read more often (faster on screen). It also allows to just route additional sensors into the tool.

TOYOCOM :: the one wire interface

 Allows to compute fuel consumption ,trip information and basic injector usage out of one added wire on nearly all early EFI toyotas, without the obd1 data stream.

benefits

• extremely easy one wire job, fast and simple.
• allows to get many information out of it
• -injector opening
• -engine rpm
• -injector duty cycle
• -fuel consumption
• -fill the built in trip computer
• faster refresh rate than regular obd1 mode

pitfalls

• loses RPM when injection stops, happens when deceleration fuel cut off occurs

*All pictures in this post have been highlighted in blue to improve understanding

TEST MULE

1997 1mz-fe V6 in an MR2  , without relying on obd2 or obd1, using only the Toyocom universal mode

PHYSICAL WORK ON THE CAR

• you need to have a toyocom as found on www.zf-scantools.com
• you need a diagnosis box with at least +B and E1 (grey and black diag boxes have it, obd2 cars might lack some pins)

1MZ-FE DIAGNOSIS box with added VF2 contact pin

install a new wire from VF2 in the diagnosis box to one injector wire of cylinder 1 (#1 or #10 on the wiring diagram of your engine. for this particular installation the last cylinder of the front bank was chosen due to the ease of reach.

A T-junction was made at the #6 wire where it was easy to reach

the same zone seen from a far before the new wire was tucked in

follow this link to understand how to open up the diagnosis box and add a new metal contact in there for your new wire

ANDROID APP SETUP

following this video you should be able to mimick the setup for your own car. resumed below are the steps.

• go to main menu
• go to display settings
• show GPS
• show VF2
• show VF2-2
• remove obd1 specific fields
• go back to main menu
• go back to main display
• click on VF2 cell
• apply injector opening sensor curve on VF2 (leave MS as the measurement unit)
• apply injector opening sensor curve on VF2-2 (swipe up on the cell to reach either RPM4,RPM6,RPM8)
• go to main menu
• go to device features
• set the tool to UNIVERSAL MODE
• set VF2 as frequency input
• set rpm channel to VF2-2
• set injector channel to VF2
• set speed channel to GPS
• press apply device config
• go back to main menu
• go back to main display
• you can additionally remove VF2,VF2-2 if you wish to clean the display, this won`t break your setup.

THEORY OF OPERATION

Free from the phone itself we get GPS moving speed.
By monitoring an injector wire we can get 2 different readings

• injector opening duration
• engine rpm

with those 3 key readings are computed injector duty cycle, fuel consumption,MPG and the trip computer data.

TOYOCOM:: Universal mode with a carburetor.

A LITTLE BACKGROUND

A year ago I was given a 1990 tercel DX coupe. It had issues to fix and I was glad to know how to.
It was then 28 years old while still showing under 100k km (about 60k miles) on the clock.

It got fixed here and there in the last year span; tires,suspension,brakes,body panels and exhaust system, engine valve seals and timing belt to name a few. The good old trusty 3E grew on me in that time lapse since it was so reliable, overshadowing the fact it is under powered to the extreme.

ENGINE OVERVIEW

It has got 82 hp and an A/T 3 gear transmission. starts like a charm on cold weather

It's an 1.5L 3E engine from 86 to 90. This engine uses a carburetor and a computer to control some peripherals and monitor it's overall operation. Very few existing sensors are useful on it, an oxygen sensor is there at least. all other sensors are switches. no analog sensors at all.(digital throttle position switch and digital temperature and vacuum switches)

The vacuum diagram is as complicated as a wiring diagram for a much more complex engine.it was the time where carburetors had to let got to full EFI.

Only E1(ground) and the VF (fuel trim) were available in the diagnosis box for the TOYOCOM to use. not even switched power (+B). Improvements had to be made to take full advantage of this setup.

GETTING  SOMETHING INTERESTING INTO TOYOBD1

An android car radio was installed to be able to gather data all the time from the TOYOCOM unit installed in the engine bay (blue box in the upper right corner of the preceding picture). this radio is setup to connect to the TOYOCOM every time TOYOBD1 starts.

• VF is already there
• E1 is already there
• +B was routed from the engine harness reaching the fuse box.
• Ox(oxygen sensor)  was routed into AB
• Moving speed is taken from the android car radio GPS

Even though there were still custom inputs available on the TOYOCOM nothing else was routed to the diagnosis box yet.

WHAT WAS LEARNED FROM TOYOBD1

• the alternator is poorly working but still operational. (battery voltage is low under all conditions)
• the engine runs rich while idling and lean when held at WOT for a long time in 2nd or 3rd gear. it might have fuel delivery or carburetor issues
• the fuel trim is always negative ,meaning the ECU suspects the fuel consumption is less than expected. It might be the oxygen sensor, might be fueling issues again. 
• throttle position and temperature switches are working OK, the system goes from closed to open loop following engine load and growing engine temperature.

WHAT IS COMING AHEAD

More custom sensors are to be mounted on the engine to even out MPG calculations reserved only at this time to EFI engines. more sensors will be added to monitor the engine tune and improve it along the way as possible.

• fuel flow sensors on fuel lines
• MPG calculations for a carbureted engine in TOYOBD1
• dirt cheap wideband oxygen sensor setup
• rpm input from the igniter