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Old 09-26-2013, 03:54 PM   #1
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Need to learn how to measure ground resistance, help please

Ok, long story not so short, engine run pretty bad or not at all. My mechanic did lots of testing and find out that MAF is fine but the ground was spiking, not constant. He was about to test ground resistance of ground wire and at the output of ECU (pin 9 of connecter 2 I think) but while getting ready for testing, everything got back perfect and engine was running good. He could never confirm if it's a short of ground wire or from the ECU generated ground.

So I had to drive back home, hoping it would never happened again. Well 2months later, it's back. So i need to check ground resistance to confirm it's the same problem again and to determine if it's the ECU ground generated that is wrong or if it's a short at the ground wire from ECU to MAF.

So, how I do that? I know nothing about electronic and electricity. I have a multimeter, what seting I set it? I have to stick the red pointer of the multimeter in the MAF connector at the brown/white wire, were to i put the black pointer? I put the key to ON position? What reading I'm looking for?

See how newbee I am, but I would like to learn. Anyone can help with a walkthrough?

Thanks
Chris
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Old 09-27-2013, 01:19 AM   #2
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Chris..
Lets just assume (?) you dont have a faulty high ECU resistance ground caused by corrosion / loose connections or by corroded battery terminals etc.etc. The ECU connection plugs must be cleaned and if its OK try the following. Before you go beating around the bush looking for high resistance connections, try this.

ADD another ground between the chassis and engine. Or from the throttle body to the engine. Any length of spare electrical cable will do, as its temporary.
Connect the temp wire / cable from a CLEAN engine or gearbox mounting bolt to the chassis - again a clean chassis bolt with no paint or corrosion. Just wrap the temporary wires under the bolt heads and snug up. You now have an alternative to the (?) faulty ground connection.

What you are doing is circumnavigating potentially high resistance faulty grounds with a (temp) new ground cables without reverting to testing out the resistance values of the existing old cables.
Let us know if you have success.
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2001 Boxster S (triple black). Sleeping easier with LN Engineering/Flat 6 IMS upgrade, low temp thermostat & underspeed pulley.
2001 MV Agusta F4.

Last edited by Steve Tinker; 09-27-2013 at 01:27 AM.
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