100mgbluep

iTrader: (1)

Ok ill check that today

100mgbluep

iTrader: (1)

An update: 92 sc300 manual with vvti coils and iginiter.

With a fully charged batter the car will only start for half a second a die. Throws codes 14, 21 and 31. As we were trying to sort out the problem the battery began to die and with a low voltage battery the car would start and run. Very strange.

Per the manual for code 14 (igf signal) i check the v at the ecu and got 5v, would this indicate that we have a bad igniter?

Ali SC3

iTrader: (10)

So code 31 is an issue with the map sensor, meaning either the map sensor is bad, or it is not wired correctly. When that happens, the ecu will read the signal as high and will dump fuel and pull timing like you are in boost.
Basically if you can get the car to run at all without the map sensor working or with a code 31, it will not run very well.

That is where the code 14 comes in, when its not running correctly, it probably is misfiring and if the ecu misses enough IGF signals (ignition confirmation) from misfires, it will shut the engine down to not flood the cylinders and catalytic converter.
Now if it never ran for more than a few seconds, or if you didn't have a code 31, I would suspect the ignitor or wiring to ignitor, but since you did get it to run (I am guessing not well with the code 31), that means the ecu was getting enough IGFs so the wiring and ignitor are probably fine.

So basically change gears and start looking at the map sensor. you should have 2.1-2.3 volts with key on engine off (reading atmosphere), and with the engine on it should drop down to 1.x something volts depending on how its running.
If it does not do that and you are seeing 5v all the time, you have a bad map sensor or the ecu is fried. this can happen if you let the 5v and ground wires touch ever while connected to the ecu.
Usually it is a bad map sensor, or the wiring is off, or the connector is loose. make sure all the pins are seated there and at the ecu. once you fix the code 31, the code 14 will stop showing up, 95% sure.

The other code is related to the o2 sensor, not as important right away but make sure it is wired right also.

100mgbluep

iTrader: (1)

Im not 100% sure that i wired the map sensor in correctly, its kind of hard to tell per the diagram which wire goes on either side of the one in the middle (depending on how youre looking at the map sensor)

Ali SC3

iTrader: (10)

look at the picture on page 1 again, it shows the map sensor with the probe facing down. look at it the exact same way and make sure its wired correct then.
make sure the key is not in or on when you do the wiring changes as you don't want to short out the 5v circuit. pull the battery cable if you want to be extra sure.

100mgbluep

iTrader: (1)

Ok ill check it this weekend when i can get back over to the car. Still curious how we could explain the low battery situation?

Ali SC3

iTrader: (10)

who really knows, the map sensor might read a little bit lower with a low voltage at the battery? somehow it misfires less?
It really doesn't matter what is happening when you have a code 31, the map sensor is the most important sensor on this ecu so it wont run right with that code.

100mgbluep

iTrader: (1)

So the map sensor was in fact wired backwards. Fixed that and while i was at it i made sure i was getting 5v to the blue wire. Plugged it all back together and still having the same result and still have the code 31.

With the fresh battery it will start for about about half a second and die.
With a really low/dead battery it will start and run very well.

Polarisman

Hey,

You need to vet out your ecu as a culprit here. The cluster of caps near the voltage regulator may be to blame as the low battery may have something to do with the voltage going to or signal from the map. Or having it miswired may have killed it.

Ali SC3

iTrader: (10)

You might have fried the map sensor at some point, I would test that or if not the ecu fried or something else is wired wrong is my guess.

100mgbluep

iTrader: (1)

Would the car run with the map sensor disconnected? (assuming all the parts and wiring is good)

Ali SC3

iTrader: (10)

It won't run very well if it does at all. 50/50 chance it might stay running is my experience and when it does it will die without throttle input. You need to get a multimeter and start checking for what's bad, ecu, map sensor, or wiring. That is about it. You did move the signal pin at the ecu to pin b62 right?
I've seen people have this code at least 6-7 times and it's always one of those. It really doesn't matter how it runs without the map sensor, it needs to read the map sensor properly.

100mgbluep

iTrader: (1)

Yessir the pin was moved over, what areas can i check on the ecu to see if its good or bad?

Sorry im not more competent with this setup, i mostly do subarus, this is my first tt ecu swap lol

Ali SC3

iTrader: (10)

I would first make sure the 5v wire is putting out 5v with the map sensor disconnected, the 2 outsde wires on the connector are 5v and sensor ground
If it is then test the map sensor output (middle wire) with a multimeter as said above with the map sensor plugged in. if you are not seeing the 2.x volts with the key on engine off, then something is fried or wired wrong.
if you are not seeing 5v at all, then make sure the pin is seated properly at the ecu (hear the click when you put the pin in the connector), a few people had that issue.

It is a map sensor with only 3 wires, but you will be surprised how many people mess it up and fry the map sensor or ecu, and then go and sell those parts.
That is why I usually tell people to check if the parts work or get it from someone who was using it on a running setup (getting harder to do).
So it wouldn't be crazy to have a bad ecu or map sensor at this point, they are all pretty old anyways by now unless you purchase them new which is pretty expensive.

you can also look up online how to troublehsoot a 2jz map sensor, its the same on all 2jzgtes and non vvti 1jz's.
There is plenty of info out there especially on supraforums, which is where I found it.

100mgbluep

iTrader: (1)

Im getting 5v to the signal wire and the outside wire with the map sensor unplugged. When i plug it in, on the signal wire (middle that runs to b62) im getting 1v that climbs up to 16v and the cycles back down to 1v. Pretty strange?