Help understanding the gt4dc citcuit for code 54

CMS-GT4

Active member
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?
 

Gary

Moderator
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)
 

**BETSY**

New member
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 :-(
 

scothaniel

New member
Hey Guys,

I used a standard Bosch 4 wire relay - nothing special.

The INT lead is what triggers the relay by giving it a ground path. DO NOT hook a 12V source to this wire directly. The ECU is only expecting a 120 - 160 mA power source from this wire.

The MTT wire either checks to ensure the relay is working properly, or is a test lead to check resistance across the pump.

M+ and M- are testing that the pump is working properly - (voltage drop).

Lev is grounded to simulate a properly functioning level sensor / switch.

For me, the light does not come on when the car is started - just when tb opens. It turns off after the car is idle for 30 seconds.

I helped wire up the 205 IC pump and level sensor on a guys 1st gen MR2 with a 205 swap. Everything was wired up, and he was still getting code 54. He replaced the ECU with another 205 ECU and it worked fine.
 

CMS-GT4

Active member
Here is a qustion.
Has anyone ever checked the mr2 ecu for this function?
Does the mr2 harness have wires coming out of mtt, m+, m- and so on? If so, I wonder if they have something built into the harness that prevents code 54, or they just removed it all together.
 

**BETSY**

New member
My MR2 ecu has no such pins and they are not shown in the ecu/wiring diagram.

I never get over this code and resorted to the rev3 ecu for my conversion.
It seems the "Work around" works on a st205 with the rest of the system in situ and allows the users to run a FMIC etc.
No such luck for us though :-(
 

CMS-GT4

Active member
I think my problem is in the relay I am using. I tried it again and nothing happend. I went to 3 part stores (napa, autozone, and advance) and finding a standard 4-pin relay seems to be harder than I thought. \
Here are the two I used. Neither of them kicks over to check for the pump.

Can someone post a relay part number so I can try and find a proper relay.

img3797qm8.jpg


thanks,
JC
 

**BETSY**

New member
It's not what you want to hear, but i to went with the easy option and bought a MR2 ecu 8)

Plug and play no more worries with error codes. sell the st205 ecu on ebay ;)
 

CMS-GT4

Active member
Bringing this thread back to life since I am going to take a whack at this again this weekend. This time I will post pictures of everything I am doing, so you can tell me if i am doing it right or wrong.
 

WannabeGT4

New member
The gt4dc diagram is ok if you have a stock ST205, otherwise you'll need to do something like this:
Code54Elimination.gif


It may be simpler to just ground the INT pin and send +12V to the two resistors.
This will only work if the ECU doesn't mind that the pump appears to be running constantly, otherwise a relay will be needed.

No relay:
Code54Elimination2.gif


If I were you I'd try it without the relay first and if that doesn't work go the more complicated route.
 

CMS-GT4

Active member
I just took everything apart and tried the light bulb method again to make sure I did it all right.

Same thing, the light is off, till I hit the gas then it comes on. The relay never kicks over to turn the light bulb on. So, someting related to the relay (maybe the INT) is an issue.

I tired the other two methods.

The relay method keeps the light off till I hit the gas, the w/o relay version does not work at all.

My issue is relay related. My INT is not kicking over the relay for some reason.

Is there a way to test that its sending a signal?
 

WannabeGT4

New member
Double check your relay connections.

there should be 12v going to the coil of the relay then from the coil to INT of the ECU. There should also be 12v going to the normally open contact of the relay and then to the two resistors going to the ECU.

If that doesn't work then the INT function of the ECU is probably burned out.
 
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