Can someone help design a 5 volt circuit
Yes I realize this is an RV forum but the post is related to wiring on my tow vehicle. I have a diagram below of what I am trying to do. But I will spell it out as best as I can first. My hope is that...
Forum Discussion
My understanding is you are trying to pull codes from a 1993 OBD1 EEC-IV controlled engine.
The neutral safety switch on the 1993 donor vehicle controlled pin 30 on the EEC. The EEC verified the neutral switch position on pin 30 prior to entering the self test mode. If the transmission was not in park or neutral it won't initiate the diagnostics sequence. Your 1977 vehicle does not have this feature. As you stated, the 1977 NSS controls the starter solenoid directly. The good news is you can force the EEC to think the NSS is controlling pin 30 by connecting EEC pin 30 to pin 46.
I assume you used the original 60 pin EEC connector during the swap and I hope you left some wire on each pin to splice onto. Not knowing what vehicle your '93 donor engine came out of the following are assumptions.
What you call 5V OUT should be STI on EEC pin 48. It's actually an input being pulled to ground to initiate the self test. Grounding this pin starts the self test sequence
What you call 5V Return should be Test Ground on EEC pin 46
Once you enter self test mode, the codes can be read as pulses on EEC pin 17
Are my assumptions close to accurate?
The neutral safety switch on the 1993 donor vehicle controlled pin 30 on the EEC. The EEC verified the neutral switch position on pin 30 prior to entering the self test mode. If the transmission was not in park or neutral it won't initiate the diagnostics sequence. Your 1977 vehicle does not have this feature. As you stated, the 1977 NSS controls the starter solenoid directly. The good news is you can force the EEC to think the NSS is controlling pin 30 by connecting EEC pin 30 to pin 46.
I assume you used the original 60 pin EEC connector during the swap and I hope you left some wire on each pin to splice onto. Not knowing what vehicle your '93 donor engine came out of the following are assumptions.
What you call 5V OUT should be STI on EEC pin 48. It's actually an input being pulled to ground to initiate the self test. Grounding this pin starts the self test sequence
What you call 5V Return should be Test Ground on EEC pin 46
Once you enter self test mode, the codes can be read as pulses on EEC pin 17
Are my assumptions close to accurate?
