Toyota MR2 Message Board - View Single Post - mr2's. fires. ground potential. what you NEED to be doing to your car right now.

TomsMR2 · 02-16-2009, 06:04 PM

if you ever dig through a toyota wiring harness, you'll find something called common grounds.. its those clusters of small diameter brown wires all crimped together and grounded in one spot. its usually 5 wires or so. again, this is for ground potential.

toyota does this to ensure that a group of sensors all has the same, equal ground. if that ground gets a little corrosion, it'll give an equal (but worse) ground to all sensors and they will read appropriately.

what we're trying to do is make the entire car a common ground with the same potential for everything.

if you want to quantify your ground quality, or potential.. you can easily check it with a multimeter for a more scientific approach.

connect a multimeter to the ground clamp directly at the battery. set your meter to ohms and test multiple spots on the car with the other probe.. to test for bad grounds, test the resistance between the negative post and the chassis of the car, on clean, bare metal.. you can test at the frame rails or something. write down that measurement, it should be very low, fractions of an ohm.

now test directly from the negative terminal to the engine block, cylinder head, and transmission. you SHOULD have an extremely equal measurement between all the engine components.. and ideally, your engine will have the same impedance as your frame rail. if your engine has more resistance, you've just verified a poor ground between the engine assembly and the frame.

you can also disprove the junky ground "kits" using this method. take a piece of metal and a block of wood or something. place the wood on your trunk and lay the metal ontop. measure resistance between the piece of metal and your engine. it will be an open circuit (no connection!). now attach a piece of wire from the block to your engine. your resistance will now be very, very low.. maybe .001 if you have an amazing meter that reads that low. now attach another wire.. still .001. and another, still .001.. and then keep in mind we're talking about components that wont be effected by even .01 resistance and you can see that adding on tons of wires does nothing

once you've got a good ground, you cant get better.

02-16-2009, 06:04 PM	#13 (permalink)
TomsMR2 Formerly Tom Brokaw Join Date: Feb 2005 Location: Bay Area Posts: 2,497 Thanks: 8 Thanked 233 Times in 168 Posts Blog Entries: 1 iTrader Rating: (0/0% )	if you ever dig through a toyota wiring harness, you'll find something called common grounds.. its those clusters of small diameter brown wires all crimped together and grounded in one spot. its usually 5 wires or so. again, this is for ground potential. toyota does this to ensure that a group of sensors all has the same, equal ground. if that ground gets a little corrosion, it'll give an equal (but worse) ground to all sensors and they will read appropriately. what we're trying to do is make the entire car a common ground with the same potential for everything. if you want to quantify your ground quality, or potential.. you can easily check it with a multimeter for a more scientific approach. connect a multimeter to the ground clamp directly at the battery. set your meter to ohms and test multiple spots on the car with the other probe.. to test for bad grounds, test the resistance between the negative post and the chassis of the car, on clean, bare metal.. you can test at the frame rails or something. write down that measurement, it should be very low, fractions of an ohm. now test directly from the negative terminal to the engine block, cylinder head, and transmission. you SHOULD have an extremely equal measurement between all the engine components.. and ideally, your engine will have the same impedance as your frame rail. if your engine has more resistance, you've just verified a poor ground between the engine assembly and the frame. you can also disprove the junky ground "kits" using this method. take a piece of metal and a block of wood or something. place the wood on your trunk and lay the metal ontop. measure resistance between the piece of metal and your engine. it will be an open circuit (no connection!). now attach a piece of wire from the block to your engine. your resistance will now be very, very low.. maybe .001 if you have an amazing meter that reads that low. now attach another wire.. still .001. and another, still .001.. and then keep in mind we're talking about components that wont be effected by even .01 resistance and you can see that adding on tons of wires does nothing once you've got a good ground, you cant get better.