1G Continuity from Sensor Ground to Chassis Ground?

[greddy_1700]

Hello,

I have a very odd problem that I am trying to track down. I recently did a lot of electrical work on my car (stripping the harness back, extending wiring, etc) and have an interesting problem. It seems my MPI circuit is cycling from various interior inputs like my turn signals, high beams, hazard lights, etc. It causes a weird spike in input to my ECU causing a lot of odd readings in Link, and causing my fuel pump even to cycle for 1 second intervals.

Long story short, I think its a grounding issue due to the wide variety of inputs that cause this problem. I started probing back through my harness, and found that I have continuity between my ECU sensor grounds (Green / Black wires) and the Chassis ground. When I probe from ECU Chassis Ground to ECU sensor ground, I see about 1M ohm of resistance. Its very high, but does show some continuity. I assume that there should be absolutely 0 continuity between these sources?

Can anyone probe between pins 24 and 101 on their ECU connectors and verify these readings?

I did wire in my IAT sensor, and Wideband and MAP sensor grounds into my ECU ground as well, but that shouldnt cause any issues?

 

[steve]

Assuming a factory 1G ECU. I measure a tenth of an ohm between pins 24 and 101 which is pretty much what I expected. Sounds like your sensor ground might have vaporized and given the behavour you describe there might be a few other issues in you wiring.

You must be logged in to view this image or video.

 

[greddy_1700]

This is helpful for sure. Is there any continuity on the wiring harness side of those pins? IE does the Green / Black wire have any continuity to chassis ground? My wiring diagrams show no continuity, but this is where I have the 1M ohm resistance.

 

[steve]

1M resistance is leakage not continuity. Someone else will have to make that measurement for you, I'm not bothering the wasps.

 

[Vegas Smith]

This is helpful for sure. Is there any continuity on the wiring harness side of those pins? IE does the Green / Black wire have any continuity to chassis ground? My wiring diagrams show no continuity, but this is where I have the 1M ohm resistance.

I can check on my extra harness tomorrow.

 

[steve]

With a harness out of a car I expect infinite ohms between the ECU sensor ground pins (17 and 24) on C-61 and any chassis ground terminal in the harness..

 

[greddy_1700]

Interesting, so this likely isn't my issue then. I was just surprised that I would see any resistance show between the two since I didnt see any connections between 17 and 24 and chassis ground. When you say leakage, where would that come from? Is it possible that its through my AEM gauges that are connected to sensor ground?

I suppose I now need to go back through the entire harness and look for anything that could be interfering with the ECU or the MPI circuit. Its a very strange issue to say the least.