Forum » EFI Wiring Fundamentals » Pull Up resistors

Pull Up resistors

EFI Wiring Fundamentals

Discussion and questions related to the course EFI Wiring Fundamentals

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Just figured I'd post this article on " floating state " and undefined voltage for anyone who wasn't exactly sure what it meant.

Admins,if this is not aloud please delete .

Nah that's great Joe, more info is always better. I struggle sometimes finding a good balance between getting my point across and not delving into too much electronic background knowledge that isn't really relevant when wiring up a car. But tech info on the forums is always appreciated! :-).

Oh by all means this course was awesome and very informative.def worth it for the knowledge I obtained .you definitely explain things thoroughly.

Will the worked examples be released anytime soon along with advanced motorsoprt wiring ?

I will also add a comment to this subject...

The term "pull up resistor" in automotive ECU language can be used to describe a couple of quite different scenarios. One case would be something like an ECU trigger input or digital input where it is used to prevent a floating input as per the article Joe linked.

The other scenario where the term pull-up resistor is used is for analog temperature inputs for resistance type temp sensors. In this case its purpose is not to prevent floating but it is actually one side of a voltage divider circuit used to convert the variable sensor resistance into a voltage. I guess a more correct term for this kind of case maybe something like "bias resistor" but it still seems common in the automotive world to call it a pull-up resistor.

G'day Adam.

Yeah, I left voltage dividers out of the fundamentals course on purpose, as creating one manually in the harness usually leads to having to generate a custom calibration for the sensor in question, and although not incredibly complex, is a more advanced topic than I wanted to go in to in the fundamentals course.

Sorry, I havent watched the video and didnt even notice this topic was related to that originally. I was more just trying to clarify to readers of Joe's post that "pull-up resistor" may have more than one meaning in automotive ECU talk. For instance the temp channel's bias resistor inside many ECU's configuration software is often labelled "pull-up".