Chassis Ground Issue 94' LT1
Thread Starter
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Joined: Jun 2007
Posts: 69
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From: Oceanside California
Chassis Ground Issue 94' LT1
We recently did a rebuild on the motor. Pulled the motor/trans and reinstalled.
Things are going well except I have several trouble codes that all led me to believe there was a ground issue.
I tested continuity to the ground going from the bellhousing/Cat hanger area to the chassis and I was right. Its not grounding to the chassis.
I then tested the negative battery to the same chassis area ground, no good.
I then tested another ground I located on the passenger side chassis and that too is no good.
Whats confusing the hell out of me is I have gone as far as to take a dremel, clean the chassis area to bare metal and I still cannot get continuity. No matter what the reading is .001 instead of the desired .000
I have tested all the other grounds and everything is working fine, what in the world is causing me all these issues with the chassis grounds?
Any help is greatly appreciated.
Things are going well except I have several trouble codes that all led me to believe there was a ground issue.
I tested continuity to the ground going from the bellhousing/Cat hanger area to the chassis and I was right. Its not grounding to the chassis.
I then tested the negative battery to the same chassis area ground, no good.
I then tested another ground I located on the passenger side chassis and that too is no good.
Whats confusing the hell out of me is I have gone as far as to take a dremel, clean the chassis area to bare metal and I still cannot get continuity. No matter what the reading is .001 instead of the desired .000
I have tested all the other grounds and everything is working fine, what in the world is causing me all these issues with the chassis grounds?
Any help is greatly appreciated.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Conventional ohmeters will not read zero ( 000.0) ohms so your measurements may really indicate a very low resistance to ground. Touch the two ohmeter test prods together and I am sure you will get the same reading as you do when measuring from the negative battery post to the frame.
Thread Starter
Advanced
Joined: Jun 2007
Posts: 69
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From: Oceanside California
Conventional ohmeters will not read zero ( 000.0) ohms so your measurements may really indicate a very low resistance to ground. Touch the two ohmeter test prods together and I am sure you will get the same reading as you do when measuring from the negative battery post to the frame.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Lets say your ohmeter is correct and the ground resistance is .001, one milliohm, that is close to what I would expect to measure with an ohmeter that CAN measure extremely low resistance, BUT....ohmeters that can accurately measure one milliohm are 4 wire ohmeters, that is, they make connection to the wire being measured with 4 total probes, not 2. Two wire ohmeters cannot accurately measure one milliohm resistance!
Thread Starter
Advanced
Joined: Jun 2007
Posts: 69
Likes: 0
From: Oceanside California
Lets say your ohmeter is correct and the ground resistance is .001, one milliohm, that is close to what I would expect to measure with an ohmeter that CAN measure extremely low resistance, BUT....ohmeters that can accurately measure one milliohm are 4 wire ohmeters, that is, they make connection to the wire being measured with 4 total probes, not 2. Two wire ohmeters cannot accurately measure one milliohm resistance!
Why would I get different readings if there is no issue?
Drifting
Joined: Dec 2007
Posts: 1,647
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From: Argillite KY
Don't worry even a little bit about .001 ohms. There is no functional difference between .001 and .000. Some meters are so sensitive that they can measure the resistance of the wire in the test leads. On these meters there is a delta-T button that can be used to zero the meter but really, there is no difference in a ground application between .001 and .000, they are both great.
Advanced
Joined: Sep 2010
Posts: 86
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From: Hampstead NC
additional info
Since I helped Tim with the rebuild/re-install, I thought it might be useful to add some more info that might (hopefully!) help: prior to engine removal, no codes, and engine idled normally. Now, when we started the car after reinstalling everything, we got a "Service engine soon" and ASR light. Very high idle, and the engine fans run full-time.
When the engine was removed, the bellhousing earth connections did rotate somewhat before we were able to secure the stud and then remove the nut to free up the earth connections -- the braided cable did lose its bellhousing terminal, which was replaced with a heavy duty crimp-on type connector.
As Tim mentioned in an earlier post, there are a ton of ECM error codes showing, and I wondered whether we had strained the grounding tab connectors that are located on the drivers side bellhousing ground point.
Also, it might be worth mentioning that Tim is using a Craftsman DVM (one of their $50-70 mid-range items) set for continuity testing (rather than resistance measurement). I have asked him to switch to the ohm ranges to see if he can get a resistance reading rather than the rather confusing 0.000 and 0.001 that he is currently seeing.
When the engine was removed, the bellhousing earth connections did rotate somewhat before we were able to secure the stud and then remove the nut to free up the earth connections -- the braided cable did lose its bellhousing terminal, which was replaced with a heavy duty crimp-on type connector.
As Tim mentioned in an earlier post, there are a ton of ECM error codes showing, and I wondered whether we had strained the grounding tab connectors that are located on the drivers side bellhousing ground point.
Also, it might be worth mentioning that Tim is using a Craftsman DVM (one of their $50-70 mid-range items) set for continuity testing (rather than resistance measurement). I have asked him to switch to the ohm ranges to see if he can get a resistance reading rather than the rather confusing 0.000 and 0.001 that he is currently seeing.
Last edited by atgordon; Nov 22, 2010 at 11:01 PM.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
I am not familiar with the Craftsman multimeter, but meters that do have a continuity function usually show the voltage across the test probes while the meter supplies constant current. Your instruction manual might explain what is being indicated in the continuity position. If you can crank the engine and the starter sounds like it is cranking at normal rpm, then your ground connection to the bell housing has such low resistance, in the milliohm range which is normal, the other problems you are having are not related to the ground connection and you need to diagnose each of the error codes to find out why they exist.
Further proof of the quality of the ground connection can be verified by measuring the voltage drop from the battery negative post to the bell housing immediately next to the ground connection. During cranking I would not expect to see more than 1.0 volt drop and probably less.
Further proof of the quality of the ground connection can be verified by measuring the voltage drop from the battery negative post to the bell housing immediately next to the ground connection. During cranking I would not expect to see more than 1.0 volt drop and probably less.
Last edited by jfb; Nov 24, 2010 at 08:12 PM.
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