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How to trace a bad wire in wire harness?


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1994 Lexus GS300 with 225,000

Check engine code bad wire harness replace.  ECU has been replaced twice.  First one lasted three weeks and then started shutting down.  Flagship One took a month to honor their warranty and send another out. But it shut down after two days.  After letting the car set for a couple of day it will start but as I said the check engine code said replace wire harness.  I have gone in internet and been told that there is a bad wire in the harness find that.  I do recall the mechanic that replace the motor had to run an wire from the harness to left side of front of motor.  So I want to know the best way to check each wire.  I know it will be a long process.  Also prior to replacing the ECU had another check map sensor and othe electrical.  I changed fuel pump, fuel filter, EGr value cleaned filter replaced, intake manifold cleaned, spark plugs replaced, 

2 Answers

With a schematic diagram, and a meter (or test light, or circuit tracer etc..).

Search Scotty's youtube channel for videos about it.


As @moutainmanjoe said you need to get a schematic for the system in which your code is for then it’s just a case of checking power and ground and continuity across those circuits to find the culprit and bypass it. Not the easiest task but it can be done