Pin 38 issue please help!!

[Talon_Man]

So when my key is off my findings are like .85 .62 volts, when pin 82 sees 12 volts pin 38 goes high instead of low and doesn’t float around 12v. Key off either pin 38 with key on will see 8.5 volts and with key off pretty much 0 volts. I have power to pin 80, 12v there and tested to see if 12 volts show up on pin 82 and they do. Fuses all been replaced, MFI is receiving 12v on both red and black stop wires however the MFI will not activate due to the weird activity from pin 38.

I also had a injector circuit malfunction and a volume air flow malfunction code before this happen. I’m to the point I believe I should send the ECU away for repair.

I’m at a loss what could cause voltage to pull up not down on a pull down circuit?
And why doesn’t it float around 12v?
And 0 volts key off weird, I think the ECU is at fault.

I heard the transistor can blow do you think that may be the problem please help.
I heard “steve” is good with the ECU operations maybe he will see this.

I have also checked the fuses under the hood and they are. Made sure voltage is present at pin 80 of the ECU connector and tested the ECU connector pin 82 12 volts on/off with key like it should.

Reason I’m asking is because the mud and check engine light used to work and suddenly just stopped. Maybe caps blew in the ECU. I opened it everything seems fine. If I jump the MFI relay, the check engine light comes on and off and I can load up DSMlink, however the car still won’t fire up. I have spark but no injectors firing I’m starting to believe the ECU grounds are damaged and I’d like to know for sure.

Any help as I know it’s not supposed to do this normally I’ll take whatever help I can get thanks

Sorry, car is a 95 GSX with the 96 style MFI harness, the one where MFI and fuel pump are separate.

 

[steve]

It took me awhile to parse your post. read it over and make sure in my editing I didn't change the points you were trying to make.

You can double check some of what you reported by disconnecting the ECU and measuring the voltages again being careful that you have the correct pins.

With the ECU disconnected you should still have battery voltage on the Blue/Green wire at ECU pin 38. This comes from the MPI relay coil pin 2 and should be there key on or key off. If you don't, since you do have battery voltage on the Red/Black wires from the MFI fuse to pins 3 and 4 of the relay, the relay would be bad or the wire shorted.

As mentioned with the ECU connected, the Blue/Green wire at pin 38 should have battery voltage at it until you turn the ignition switch on which should provide battery voltage to the Black/White wire at ECU pin 82 and in response to this the ECU should pull the Blue/Green wire at pin 38 to ground. If it doesn't the most common cause I've seen is from a wiring error that put straight battery voltage on the pin without any current limiting (resistance) blowing the transistor in the ECU that trys to pull the pin to ground.

Since you can get the ECU to boot by forcing the MFI relay on (grounding ECU pin 38/MFI relay pin 2) and connect to DSMLink, you should get a log making sure to include both KeyOn and KeyStart in addition to the normal parameters to make sure the ECU is seeing these inputs.

dsmlinkloggableparams [ECMTuning - wiki]

www.ecmtuning.com

Please make sure your posts are readable or I won't be able to respond.

 

[Talon_Man]

Okay I will read your reply and focus on your information as I’m very appreciative of your input I’ve seen you all over the forums and I know your input is valuable so.. I will go over everything you said and post results late tonight or tomorrow
Sorry my post was all over the place I’ll try and keep it more simple so it’s easier to follow

I will post everything until resolved as this may help some one els figure out a similar problem thank you steve

 

[Talon_Man]

Okay so update I know I’ve been slow on the results to this topic I work full time as a technician I know I know then you should be able to figure it out …. I am going to go over what steve said in the next few days I will update results sorry I haven’t been able to get the information for you I will soon tho as I very much appreciate the help I miss my dsm !!

 

[Talon_Man]

Found the problem I believe, sending ECU to Tom @ ECMTuning. Awaiting their findings but that look’s like corrosion to me.

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[Talon_Man]

Okay for any one who is wondering when your mfi relay won’t activate he’ll send out the ecu I was right the ecu was messed up here’s the after of the above repair in the pictures I am going for start up tomorrow

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[Talon_Man]

Okay so a little update on the car I got the ecu repaired but then started to question the wireing so this happpen as you can see in the pictures I’ve decided to rewire the whole car with a factory oem harness I’m wrapping this up soon I’ll post a running video on the the before and after thanks to all who are still following hoping to see the check engine light come back and everything start acting normal again wish me luck keep you all posted

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