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After a long time off the road, OHM-RIDE seems to have finally been repaired (see details on this thread)

The conclusion by the GM engineer and the repair technician is that a set of LED fog lights I hooked to a ground was considered the ultimate source of the problems. Why it would become a problem after many months I don't know but there it is.

So I wanted to give a heads up to all Gen 1 Volt owners that if you are having odd computer glitches of any sort one part of your diagnosis should be to check the "critical grounding stud" shown in the photos below and make sure it's free of corrosion and tightened up properly.

Also, according to the GM engineer, NEVER attach any aftermarket items to this stud, leave it alone, period!

Seriously, if it's so damned sensitive and important I don't know why it's not painted a warning color, or covered, or placarded with a warning label or something, but it isn't.

So for future reference to all other Gen 1 Volt owners....





 

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Having multiple grounds can cause multipathing issues and crash computers easily. Even in an older transistor component stereo system, multiple grounds can cause feedback loops even as far as causing hum in the speakers. (re: "single point of failure design" caption)

Since you are probably grounding back through your load to where ever you picked up the power feed or the through the lighting mount point, I can see this causing huge issues.

One thing that all technicians should look for: non-standard customization. It is usually the last thing touched that causes a new issue. All circuits should be normalized back to stock before diagnosis begins.
 

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Thanks for letting us know and depicting it so well. Very good to know.
Kind of crazy that a disturbance there resulted in significant loss of braking power.
I wonder if the same grounding issue was related to the older topic about how one owner's HID upgrade was suspected as causing his loss of brake power (maybe he grounded a relay there).
 

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Discussion Starter #4
Having multiple grounds can cause multipathing issues and crash computers easily. Even in an older transistor component stereo system, multiple grounds can cause feedback loops even as far as causing hum in the speakers. (re: "single point of failure design" caption)

Since you are probably grounding back through your load to where ever you picked up the power feed or the through the lighting mount point, I can see this causing huge issues.

One thing that all technicians should look for: non-standard customization. It is usually the last thing touched that causes a new issue. All circuits should be normalized back to stock before diagnosis begins.
The feed was direct from battery supply through switch, lights, and to ground.

I would agree on the feedback loop thought (I'm an IT tech) except that if it's all bonded to the car body it really shouldn't make a difference. Regardless, If I'd known that the nice, conveniently located, stud was for the computer ground I wouldn't have touched it.

In short I REALLY wish it had been labeled, or even better, covered in some fashion.
 

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The feed was direct from battery supply through switch, lights, and to ground.

I would agree on the feedback loop thought (I'm an IT tech) except that if it's all bonded to the car body it really shouldn't make a difference. Regardless, If I'd known that the nice, conveniently located, stud was for the computer ground I wouldn't have touched it.

In short I REALLY wish it had been labeled, or even better, covered in some fashion.
This is why people shouldn't use the car body as ground. There are isolation points that may interfere. When running an accessory, run a hot and a ground back to the battery (if a large load) or back to the buss bar for the circuit breakers/fuses. Yep, a small load may be done to the accessory outlet, but, even then mounting a transmitter or radar detector near other gear may cause issues.

Tapping directly into a circuit on a modern (CAN Buss) car can also cause issues since the impedance/capacitance/load could interfere with the circuit's design. This is exactly why some cars need extra circuitry to run trailer lights. Can't just tap into the tail lights any more.
 

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That's G117.
The only thing that grounds there is the Electronic Brake Control Module (EBCM) nothing else.
Pretty sure the dealer would have checked that ground for an EBCM communication issue
Aftermarket installation guidelines prohibit connecting directly to OEM ground points.
These guidelines dictate a dedicated ground point be used or directly to B-

Funny, but you never happened to mention any aftermarket equipment in your other thread.
But, the dealer should have seen and removed your grounding wires when there were issues with EBCM comms (U-codes)

All grounds are critical. lol That ground is really no different or any more important than the many other grounds on the Volt.

In any case I'm glad you got your car fixed, but we're not going to let you post misinformation as like I said, that ground is strictly for the EBCM and no different that any other ground.

WOT

Nothing more to see or say here. Thread closed.
 

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