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Unread 01-07-2013, 02:16 PM   #1
sunrcr69
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Hemi TB Ground wire - Not a good idea

I was lazy today and took my 05 5.7L WK to the dealer for an oil change. They did their little inspection to sell me more stuff and saw I had installed a ground wire from the throttle body to the ground point on the body that the battery uses. They informed me that they have seen a few people do this and that its a bad idea because the TB gets its ground from the ECU which provides a RF shielded signal (shielded from radio interference). Anyone who has messed with aftermarket stereo equipment knows what this is. They continued saying if the TB is grounded to the body or battery, interference may alter the signal to the TB and cause a WOT (wide open throttle) condition.
Since this is a fly-by-wire configuration and my life and the lives of others are involved, I have since disconnected my TB ground. It didnt seem to do much anyway and I dont want to chance killng someone, my family, or myself for any trivial gain I may have got from this mod.

Whether this is true or not, I recommend others do the same, its not worth it.

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Unread 01-07-2013, 02:59 PM   #2
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Maybe, maybe not. Depends on whether "sensor ground" (pin 6) is connected to the case of the TB or not. I never got around to ohming it out.

...tom
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Unread 01-07-2013, 03:51 PM   #3
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I was unaware that a ground provided a signal, RF shielded or not. Still got mine connected.
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Unread 01-07-2013, 04:17 PM   #4
w1pf
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If the sensor ground is connected to the case of the TB, it will craete a ground loop and it could indeed affect the signals back from the TB. THe ground is indeed part of "the signal"

If the sensor ground is NOT connected to the case of the TB, then grounding the TB could help shield against noise.

...tom
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Unread 01-07-2013, 08:44 PM   #5
DRCracker
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I remember that before I installed a TB ground, I checked to see if the TB was already grounded, and it was not.

Now, I can't remember if I checked it with the engine running, but I'm pretty sure I checked it with the engine off.

Seems to me that it the TB was not showing continuity with ground before I installed the wire, then the "sensor ground (pin 6)" wasn't previously connected to the TB.

Does this make sense?

TC
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Unread 01-07-2013, 11:19 PM   #6
sunrcr69
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Quote:
Originally Posted by w1pf View Post
If the sensor ground is connected to the case of the TB, it will craete a ground loop and it could indeed affect the signals back from the TB. THe ground is indeed part of "the signal"

If the sensor ground is NOT connected to the case of the TB, then grounding the TB could help shield against noise.
If the sensor is NOT connected to the TB case, grounding it could introduce noise from the ignition coils or alternator which are grounded to the motor which is grounded to the body. That's usually where RF noise comes from.
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Unread 01-07-2013, 11:48 PM   #7
Joeyicu
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I think you would have a higher chance of getting stuck by lightning while driving to collect your multi million dollar lottery winnings.

Think about this for 1 second, a commanded WOT, what kind of level of stray RF would you have to see for that WOT condition to happen, uncommanded. I think the dealer was just doing the dealer duties to keep the truck stock as they can, and if you have a general safety concern about you and everyone around you, kudos mate.

On the flip side of this coin, what the poop would putting a ground wire on a TB do to effect performance at all? Can someone clue me in?
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Unread 01-08-2013, 12:21 AM   #8
trax95008
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I questioned the validity of this mod myself a while back. It seems to me, that if it really made a difference, it would have been cheap and easy for the engineers/manufacturer to do themselves. I to tested to see if the TB was grounded or not and it wasn't. I grounded it and didn't notice any difference. I agree that most dealerships and their mechanics are idiots, but this does have me thinking. Maybe it's not grounded for a reason. Who are we to question the engineers? I think I will remove mine knowing that it was designed to function properly without it. I do have my kids in the jeep often after all...
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Unread 01-08-2013, 04:04 AM   #9
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Quote:
Originally Posted by sunrcr69 View Post
If the sensor is NOT connected to the TB case, grounding it could introduce noise from the ignition coils or alternator which are grounded to the motor which is grounded to the body. That's usually where RF noise comes from.
Grounding the case is far more likely to shield from such noise than induce it, unless the ground wire is very long. Then again, IIRC the sensors/motor aren't actually 'inside' the metal part of the TB so it probably doesn't matter much. I've never taken an engine through RFI/EMC certification, but I've taken many electronic products through and have quite a bit of scar tissue related to grounds

Given that a ground strap is not free, it is unlikely that it would have been designed in unless it was necessary, which is clearly is not. Whether it makes any improvement is up for debate, but if the case wasn't already grounded thru the sensor ground (as measurements here indicate), then grounding it isn't going to hurt anything IMHO.
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Unread 01-08-2013, 07:10 AM   #10
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I feel way to many people have done this with out any problems for this to be true.. I havent done it because I dont see any gain from what people say.
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Unread 01-08-2013, 08:23 AM   #11
sunrcr69
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Quote:
Originally Posted by Joeyicu View Post
I think the dealer was just doing the dealer duties to keep the truck stock as they can, and if you have a general safety concern about you and everyone around you, kudos mate.
This crossed my mind while the Service Manager was giving his speech.
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Unread 01-08-2013, 09:46 AM   #12
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When I did my TB ground (about 2 weeks ago) I noticed no change at all, although I did not expect any. I'm just trying to future-proof my electrical system. Given the quantity of non-specific electrical issues reported on this forum, I'm willing to ground ANYTHING, if it will help dissipate what I view as the propagation of standing waves.
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Unread 01-08-2013, 12:06 PM   #13
sunrcr69
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In my first post, I said it could cause a WOT condition. What I meant to say is it could alter the signal to the TB and what the driver is doing with their foot may not be what the TB actuator is mimicing. The result could be WOT, could be a closed throttle or anywhere inbetween.
This is what the dealer said, I am just relaying the message.
Do with it as you will.
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Unread 01-08-2013, 01:08 PM   #14
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This phantom throttle open reminds me of when Camry owners were having their mats slip off and floor the accelerator.

You do realize that if wot were to happen, you just push the transmission into neutral and catastrophe avoided.

I couldn't believe hearing about people calling 911 from their camrys because their pedal was stuck. It's a shame but every automatic car has this design.
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Unread 01-08-2013, 02:16 PM   #15
sunrcr69
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Quote:
Originally Posted by blizzboy283 View Post
This phantom throttle open reminds me of when Camry owners were having their mats slip off and floor the accelerator.

You do realize that if wot were to happen, you just push the transmission into neutral and catastrophe avoided.

I couldn't believe hearing about people calling 911 from their camrys because their pedal was stuck. It's a shame but every automatic car has this design.
of course, but IF this could happen, I would not trust my wife driving with my kids or someone else on the road with a WK knocking it into neutral. Most people panic.
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