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Old October 12th, 2017, 17:28
JeepNoob JeepNoob is offline
NAXJA Forum User
Join Date: Oct 2014
Location: Pueblo, Colorado
Posts: 376
Re: Tracking a Short Help Requested

For what it's worth (and future reference), there's two kinds of shorts- a short to ground and a short to power.

For most folks, a "short" is short for a short to ground. That is to say a wire with voltage flowing across it somehow connacted a body panel, a ground wire, the enhine, a metal part attached to the engine, etc. The most common symptom of a short to ground is a blown fuse. That's what they're there for. When the wire shorts to ground, it wants to pull as much amperage as it can (which is as much as the battery will provide.) Ever accidentally welded a wrench to battery terminals or when you were trying to remove a starter? You get the idea. To trace a short to ground, I like to break the circuit into as many "pieces" as possible by disconnecting connectors. Then I break out my DVOM, set it to read resistance, and starting poking around. Place one lead on the wire or "piece" of the circuit you want to test and the other on a good ground point. Pretty much any old sheetmetal bolt should work. An "OL" reading indicates "these are not the droids you are looking for", but low resistance indicates you have found the "piece" of the circuit that is shorted. A good, visual inspection of said piece should reveal the short.

A short-to-voltage is a little bit different. This is when a circuit that have a set amount of voltage or variable voltage becomes shorted to a circuit with more or non-variable voltage. A great example would be the signal wire gor a TPS shorting out to the 5-volt reference wire. Indeed, sensor circuits are the most suspectible to shorts to voltage, and as a result, the most common sign of one is a CEL with an associated DTC. However, the same basic rules apply- break the shorted circuit into "pieces", break out your DVOM, but test for voltage on the circuit instead of continuity.
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