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

TOYOCOM :: Universal mode on the AW11 blue top 4A-GE

WHAT'S THE BIG IDEA

Having modern day diagnostic features on an car is very useful. On a +30 years old car it is a luxury that is rarely found. For Toyotas there is hope now. Using the toyocom 'universal mode' you can get a fair level of information out of our  mid 80s toyotas.

Doing so requires of the car owner to do some electrical work to splice into signal wires we care for. A compromise was made to leave the wiring harness untouched. It may be more ambitious but certainly not out of the reach of the DIYers.  What requires to be done is to solder wires on the underside of the ECU main board, exactly where the ECU connector are soldered. This location gives us acces to every wires going into the ECU and is conveniently labeled on most toyota ECUs.

RANDOMNESS STRIKES

Believe it or not, while working on this blog post a friend passed by with a beaten up mr2 while being in transit to somewhere else. It was shear luck,so we took the time and tried the modified ECU on it!
The car was in really bad shape but running,no exhaust with the blue top 4A-GE not running on all cylinders. we were able to get our readings while being quick at it to not wake up the city neighbors.

WHAT YOU CAN EXPECT IN THE ANDROID APP

mandatory features from universal mode on an early EFI toyota.

• Error codes readout
• battery voltage
• fuel trim

mandatory wires you have to solder

• B+ 12v power
• E1 ground
• T (TE1) trigger error code output
• W check engine light
• VF (VF1)  fuel trim

additional wires you should monitor before anything else

• IGT this is the igniter control (for RPM input)
• #10 this is the first injector pair control
• VS  this is the air flow meter output
• OX this is the oxygen sensor
• THW this is the coolant temp sensor

reasoning

• having RPM & injector activity allows us to get injector duty cycle
• having the air flow reading tells us about the engine load which is always useful.
• having the oxygen sensors allows us to troubleshoot fueling issues against engine load & rpm
• having coolant temperature allows us to know if we overheat and guess the fueling choices.

WHAT YOU NEED TO GATHER

• a toyocom scan tool from www.zf-scantools.com
• a spare ecu for your engine is best.
• a junk yard diagnosis box, preferably a late black one from an obd2 toyota.
• new contact pins from digikey (only usable with the late black diagnosis box)
• 10 wires of different colours. about 1' long 20ga

WHAT REQUIRES TO BE DONE ON THE ECU

To understand how to install contact pins in the diagnosis box follow this earlier post.

where each wire goes in the diagnosis box

ORANGE                =         +B
RED                        =         VF1
DARK GREEN        =         E1
NORMAL GREEN  =         AB
YELLOW                =         W
WHITE                    =        TE1
BROWN                  =         TT
BLACK                   =        TS
BLUE                      =        TC
PURPLE                 =        VF2

• install contact pins on each new wires you need  ( a feet long is comfortable to work with)
• place the wires in the diagnosis box at the specified spaces in the top cover

• Add a shrink wrap sleeve to your new bundle of wires
• Remove both top and bottom ECU cover plates
• on the TOP side,read the labels for the connector pins to know where your signals are located.

YOU WILL BE SOLDERING ON THIS SIDE

where each wire goes on the ecu connector

ORANGE goes to +B
RED goes to VF
DARK GREEN goes to E1
NORMAL GREEN goes to VS
YELLOW goes to W
WHITE goes to T
BROWN goes to THW
BLACK goes to #10
BLUE goes to OX
PURPLE goes to IGT

Overview of the work done ot the ECU

PLEASE EXCUSE THE HASTY SOLDERING

• solder each wire to it's matching pin
• reinstall the top cover plate.

• Applying hot glue with a glue gun over your work is suggested for shielding and dampen vibrations.

before installing the bottom plate you want to add washers to shim the cover and use longer bolts to compensate, doing this drops the chances of the wires cutting themselves due to friction.secure the added wires to the ECU case using hot glue, to lock them in place.

• connect your ECU to the car and the toyocom into the diagnosis box.
• at this point follow the toyocom user manual given with the tool to start using it.