Seems like a silly question maybe but after slightly tugging on pin21 last night, now I cant start my car....

The fuel pump will engage for a split second but wont fully prime before cranking so I'm wondering if I pulled the ground wire loose from the ECU pin or worse from the harness. I did not tug on this hard at all which is the weird part, I simply pulled the wire out of the electrical tape I had wrapped around the wires for plug D.

Anyway...I took a voltmeter and tested a switched 12v source and took the negative probe of the voltmeter and tested pin 21 & 22 on plug D and it doesnt register 12 volts like a chassis ground would. The results are .01-.02 volts so I didn't know if this was normal or not.

I know the sensors and ECU dont utilize all full 12 volts current since electronics normally operate under low voltage but I'm trying to diagnose if this would count as a grounding issue since D21 (sensor ground) would also be used for say a wideband 02 ground for up to 5V although I'm not trying to hook up a wideband for which I already have.

 

We'll I found the answer to my question.....I plugged the D connector into the ECU and tested the voltmeter probe on D21 & D22 led's on backside of the ECU connector as shown and got a full 12volts on both so looks like i'm dealing with another issue.....

 

Is the pin all the way into the connector? Take the pin out maybe its broken.

 

If a circuit runs on 12v its using that much voltage. Its the current that varies.

Think of water pressure in a pipe.

The pressure is the voltage, the amount that flows through the pipe is the current. If there's a restriction in the pipe that's the resistance.

That's why some wiring is smaller than others. Its based off current not voltage.

 

I found out what the problem was.....completely unrelated. The issue was the ROM that was used. I had burned a ROM to my chip last night also and the image must have been lacking an advanced option from Crome such as the P30 option byte hack or something but I tested cranking the car on a known working image I had saved and it cranked right up with no issues so I just rebuilt the current image with the table values that I was testing along with all the proper advanced table features.

I cant explain how the ROM with issues could have lost these settings or maybe it became corrupted somehow but went undetected since the image was able to be pulled from Crome but the issue is resolved...

I suspected that the sensor grounds could have been an issue since I pulled the wire loose from electrical tape wrapped around the wires on plug D last night but never cranked the car until today.