While replacing my heater hoses I noticed this green wire that had been pulled out of the engine harness, cut, electrical taped, and tucked down behind the wiper motor. This is right before the harness passes through the firewall. I can't tell what this is, or what effect it might have been having (my car is 2 months on jack stands replacing, fixing, tightening, cleaning and demystifying my engine bay).

Wiring diagrams for the engine harness show green for the IAT and crank angle sensor, but I'm not sure that the car would have ran without either of these, and the ECU wasn't throwing any codes. Weirdly, I get continuity between this wire and every connector on the harness, and also any point on the engine block (though not the chassis). I haven't figured out how that is happening.

 

Do you have more history on the car?
Perhaps the previous owner used it as a sensor ground. That’s what it looks like to me.

 

Green wire = not OEM Mazda

 

You're gonna need to trace that thing. Getting continuity readings like that on a wire that was added is not good. See if you can get lucky and look down by the ecu. Maybe the other end will be visible

 

Not much history on the car unfortunately, I've been uncovering a lot of hacking though so an added wire kind of fits the profile. This gives me some new leads (get it?) thanks guys.

 

Might just be a replacement firewall ground strap that often breaks over time. From the factory it's a braided jumper between the uim and the firewall.

*disregard, didn't realize it originated from the engine harness

 

Yeah that's an aftermarket wire someone added in. You'd probably need to put in a ton of effort to unwrap the harness and see what it's tapped into, if the car is running and driving OK just tape it up and move on.


Dale

 

Yeah, no signs of the other end, so knowing it's not OEM I can leave well enough alone.