Help understanding the gt4dc citcuit for code 54

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Postby Gary » Mon Nov 06, 2006 6:49 pm

Another throry, every relay has internal resistance.
Thus, if you connect INT to 12V directly, the ECU (if it's that smart) could realize that there is somthing wrong.
Try put a small resister on the INT line and see if it works.
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Postby CMS-GT4 » Mon Nov 06, 2006 6:59 pm

Already tried that with a 3rd 1k resistor. I hate code 54...
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Postby CMS-GT4 » Tue Nov 07, 2006 2:34 pm

I m just going to use the light bulb route. Only problem now is that they no longer print the wattage on the package or the bulb.

So as soon as I find a 10 W bulb, I will wire this up and call it a day.

Went to the website to get a part number for a 12v 10w bulb. So I will go pick it up in the morning.
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Postby CMS-GT4 » Thu Nov 09, 2006 12:22 am

:x :x :x :x :x :x :x :x :x :x :x :x :x

So.

I hooked it up exactly how scott did and I still get code 54. Its off for a few seconds then turns on.

Does it matter the kind of relay I use? I pullede a 4 wire relay out of my st205 fuse box.

The light comeson when I turn the key to acc, but shortly after starting I get code 54....

I also treid a variation of things to make this work. Even mixing resistors with bulb.
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Postby Gary » Thu Nov 09, 2006 3:58 am

:shrug:
That ECU has a mind of its own. :shoots:
Sell the damn ECU and get the MR2 one.

Someone with ST205 and FMIC setup please check the voltage at each terminal for him....
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Postby CMS-GT4 » Thu Nov 09, 2006 6:07 pm

Does the amperage of the bulb matter? They took forever to find a 10W 12V bulb. They did say the amerage was sorta weird on it. Its a jetta bulb.

If I knew the amps required, I could get a resister thats the same value as a 10W bulb.
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Postby hacker_720 » Thu Nov 09, 2006 8:07 pm

P= VA
10W = 12(A)
A = 10/12
A = .8

I can't see the amp mattering for the ECU, it's just sinals, it will be like 2-40mA (0.02 - 0.40 amps) so that bulb will probably work for you.
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Postby hacker_720 » Thu Nov 09, 2006 8:11 pm

oh.. sorry. resitance...

V=IR
12 = (.8)R
R = 12/(.8)
R = 15

yup thats about right, I aggree a bulb is probably 15 ohms

what you really want to know is what is the resitance of the sensor in the IC then just put that resistance in, don't get carried away with the old bulb trick.
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Postby hacker_720 » Thu Nov 09, 2006 8:16 pm

CMS-GT4 wrote:Here is an image and reply from Kris (Who did the writeup).

Hi JC,

glad you find the article fairly useful...so far! Not so good is that you are having problems getting it to work for your particular installation.

I fear that the control of the pump is a bit tricky and on the 205 this is not a straight forward solution, unlike the 165 and 185.

For the stock setup on a 205 the article I wrote works fine. The IC level sensor is bridged and the resistors are added to the wiring AT THE PUMP.

The monitoring of the circuit so that the ECU does not throw a code is open for debate, and I know that this has been tried before, without success

I have a diagram I sent to someone before and can send you that may help? Please drop me an e-mail to kris@gtfours.co.uk and I'll reply with the diagram.

The solution may work around when the ECU activates the pump relay, and using this signal/voltage may help.

For background info the pump operates like this on the stock 205:

Press throttle - pump starts and runs all the time the throttle is pressed
Throttle released - pump continues to run for 30s and then stops
Throttle pressed - pump runs again

Hope that helps?


The image looks like the circuit we made at the ecu.

Image

Sofar what it looks like is I prevent the code at startup. So it much check for the LEV first, then it checks for the connected curcuit. Which is why at start up and idle the current setup at the ecu keeps the light off. Once i get ovre 1700 rpm, the relay activates the pump which looks for the pump working. So somehow for this to work at the ecu, I think the INT needs to trip a relay that might send a signal to MTT, M+ and M-

What I wonder is, if at idle the base value is fine, is just needs to change. So maybe a relay with a different resistor. Activated by INT then a resisted 12V passes through the relay to the rest of the cucuit.

If I can't get this to work, then I will just do the light bulb method.


this is wrong, that 1k resistor that is going from ground to 12v is not doing anything.
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Postby CMS-GT4 » Thu Nov 09, 2006 11:03 pm

Update.

I was working on it again. I started all over again from scratch to do the lightbulb method.

So here is the thing.

INT acts to trigger the relay. INT is not supposed to trigger the intercooler relay till you press the gas. Yet the light turns on as soon as the key is set to acc.

I though something did not seem right. So I started messing around.

I decided to switch the INT trigger wire with the lightbulb. I turned the key on and the light did not come on. Either I was reading this relay wrong or its printed backwards.
However, the cel stayed off till I hit the gas.

So anyway. I think the relay is broken. I just used an old relay out of the st205 fuse box.

I am going to get a new relay in a few and see if that works.
Coldiron
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Postby CMS-GT4 » Sat Nov 11, 2006 1:24 am

So I got a relay. Maybe I am just plugging it in wrong. Maybe the wrong kind of relay. The relay looks for a gound to close.

I do not think INT grounds the relay does it?
Coldiron
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Postby Gary » Sat Nov 11, 2006 2:13 am

I don't think the INT is directly grounded.
There might be more stuff inside the ECU.
(like switching circuit to turn the pump on)
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Postby **BETSY** » Sat Nov 11, 2006 7:21 pm

Hi Guys, tried all the above to make the st205 ecu work on my st165 and never got it to work :-(

I bought a mr2 ecu.. car fires up great no error codes but runs only for a couple if seconds then dies :-(
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Postby CMS-GT4 » Sat Nov 11, 2006 7:53 pm

Did you move the pins around? I think the mr2 has a few pins differnt on the ecu.
Coldiron
92 st185 (205 swap) | 03 350Z Track (sold) | 13 Pilot | 17 Mazda3
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Postby **BETSY** » Sat Nov 11, 2006 9:44 pm

hi, the mr2 pins are not needed on the celica set-up..
its a Lil bugger thats for sure!
Steve Gillies
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