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Ok sport fans, this one is driving me and the dealer nuts. 

 

1.  Gauges, especially the tachometer and speedometer go down.

2.  Shifting is super erratic from a standing start, kinda like -- shift-  -bump- - shift -- bump, really erratic.

3.  Steering goes to nothing!  Very difficult to  turn vehicle, if at all.

4.  When this issue first started, the engine, if turned off, wouldn't start for a few minutes.  

 The dealer initially diagnosed the problem as a bad ground cable and replace it.  I had them replace the battery harness, supplied by me.    Now as one is going down the road, the system goes nuts, then after a few minutes, goes to normal mode.  Then its OK for the rest of the day.  

The original tech tested the battery and its supposed to be OK.  The truck has 47400 miles and is on the original battery.  The voltage gauge indicates 14 volts while running.  I have heard that the battery may be the culprit, the truck upon initially starting in the morning, kinda turns over too much, at least to me.  Runs OK after it starts.  Its damn cold here in Amarillo today, like 9 degrees!  So does anyone have any ideas?  

I did have a electrical gremlin in my 2002 C-5 until I put a Optima Red Top in it.  Makes me wonder now about my truck.  

 

Thanks ,

 

Jon

Edited by Chicken Heart
Forgot my name.
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9 minutes ago, Chicken Heart said:

Ok sport fans, this one is driving me and the dealer nuts. 

 

1.  Gauges, especially the tachometer and speedometer go down.

2.  Shifting is super erratic from a standing start, kinda like -- shift-  -bump- - shift -- bump, really erratic.

3.  Steering goes to nothing!  Very difficult to  turn vehicle, if at all.

4.  When this issue first started, the engine, if turned off, wouldn't start for a few minutes.  

 The dealer initially diagnosed the problem as a bad ground cable and replace it.  I had them replace the battery harness, supplied by me.    Now as one is going down the road, the system goes nuts, then after a few minutes, goes to normal mode.  Then its OK for the rest of the day.  

The original tech tested the battery and its supposed to be OK.  The truck has 47400 miles and is on the original battery.  The voltage gauge indicates 14 volts while running.  I have heard that the battery may be the culprit, the truck upon initially starting in the morning, kinda turns over too much, at least to me.  Runs OK after it starts.  Its damn cold here in Amarillo today, like 9 degrees!  So does anyone have any ideas?  

I did have a electrical gremlin in my 2002 C-5 until I put a Optima Red Top in it.  Makes me wonder now about my truck.  

 

Thanks ,

 

Jon

Personally, I would swap for a new battery.

 

Life span for the factory ones are pretty short, and as they get weaker, it causes havoc on the electrical system.

Had to replace batteries in my 14 and our 16 Tahoe in less than 18 each.

 

Welcome to the site!

Edited by JimCost2014
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25 minutes ago, Chicken Heart said:

Not a bad idea.  I will wait until I get the truck back then swap out the battery.  Funny, it has these issues when its cold.  Is fine after the weather warms up!  

Jon  

Extreme cold and heat are your batteries second worst enemies, with age being first.

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Forgot to add this note from the dealer. 

 

Concern / cause: Scanned alot of no communication to ecm and tcm in a lot of different modules.  gr8 battery test, battery tested good.  Preformed voltage draw test, positive passed with 72.  Negative battery cable failed with 309.     

Correction:  Dielectric grease the ecm, negative battery cable replaced.

 

So thinking, I will locate the service bulletin PIT5405A, read it ans research the G218 code.  I think I will replace the battery when I get the truck back.

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In doing some searching, I found some other fixes to resolve my issues as done by other owners.  Apparently what they have done to rectify the problem is to place additional negative grounds.  All these are from the negative battery terminal.  One cable to the trucks frame, another to the engine block and finally one to the body itself.  They all advocate making a positive grounding area, i.e., grinding a spot for the new ground, using "Earth bolts"? etc.  All have to be run thru the existing ground cable sensor located near the battery. 

 

What we in the hotrod world (At least mine anyway) usually do is to run the negative cable to the frame, another from the engine to the frame and one from the body to the frame.  In the case of fiberglass bodies, from the grounding panel or terminal block inside the car to the frame or engine block.  The alternator is grounded to the engine block also.  (extra wire)  Now considering that these cars usually don't run sensors at all, mayhaps those suggestion of running the extra cables to resolve these grounding issues on these new vehicles isn't such a bad idea?  Thoughts on this?  I'm waiting for the dealer to call and tell me they found the issue with my 2016 GMC.  

Edited by Chicken Heart
spelling and grammar
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2 hours ago, Chicken Heart said:

So thinking, I will locate the service bulletin PIT5405A, read it ans research the G218 code.  I think I will replace the battery when I get the truck back.

This.

 

G218 is not a code -- it's the ground stud.  There was an issue where during assembly they pinched some insulation between the nut and the metal part of the dash.  There are videos on youtube showing how to check the G218 ground.  It is really easy to do yourself.  The G218 is on the driver's side but while you have the dash cover off check the one on the passenger side too.  Even though I didn't see any material caught under them I removed both ground nuts, sanded the underneath of them and around the base of the stud, and reinstalled them tightly.  It took me about 20 minutes total to do both.  I have not had any electrical issues since ....

 

P.S. -- I attached an old revision of PIT5405.  Your dealer should have access to the latest version.

PIT5405D (18-NA-161) Electrical Issues.pdf

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Thanks, now I have both bulletins.  To date, this morning, they haven't been able to replicate the initial issue.  I called the dealer and spoke with my service writer and told her that if they couldn't replicate the issue, I'd pick-up my truck this afternoon.  I inspected the battery harness and was not surprised to see not much of a terminal connection, i.e.; dirty and rusty?  Hmmm -- - .  Hopefully when the service tech installed the new one he did it correctly.  

 

So I will replace the original battery (if need be) after I drag out my old "Toaster"  and check the battery condition.  There are times when the old service tools work better than the new handy dandy stuff.  As it has been explained to me on numerous times by my computer / programmer friends, anything with a hard drive or software, tends to wear out more so than good old fashioned  camp fire and a blanket to send messages!  

 

Have a good week and thanks for the reply.

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Well here's the latest on-goings with my truck and it's issues.  i couldn't find the G-218 grounding points even after removing the side trim, using mirrors and flashlights.  If its there, its well hidden.    The system keeps going down and after repeatedly talking to my dealer service reps haven't gotten anywhere.I haven't been able to talk to  the service manager, but even after giving them the service bulletin that reflects all my trucks issues, they apparently don't care. Hmmm- - - So on Thursday of this week, running about 70 on a portion of Amarillo's 335 loop, the thing went dead to include the engine stalling out on the west curve!  Now that was interesting to say the least.  So -- - - - - - I called the customer support of GMC and filed a claim as my truck being unsafe.  After a lengthy discussion of what has happened (good thing I document things) the dealer where I was , as I see it, being blown off, because they couldn't replicate its issues.  They gave it a priority status and gave me a claim number and was told they should be in touch within 7 days.  

 

I did load test the battery and it tested very good.  Then I took the thing to Auto Zone and had them load test it.got the same results.

So- - - - if I don't hear from GMC in the next week, we will add a battery ground to the frame, engine to the frame and from the cab to the engine/frame.  Any other ideas  would be greatly appreciated. 

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sounds like my 17 that got lemon lawed for a very similar issue. They replaced both pos and neg cables, fixed those ground points, repinned comm lines on modules that were dropping out, replaced modules, replaced wiring harnesses, etc. Would be fine for a few days to 3 months 100 to 3000 miles, hit the smallest pothole on one side of the truck to make it jiggle and spaz city. Gauges go to zero, service: 4x4, trailer brake controller, stabilitrack, ABS, and steering input reduced. Hit another bump and it would come back. Last 2 times it did it the power steering went out too. Refused to start on several occasions because it didnt know where the gear shift was. Ive got a video i could upload.

 

If adding grounds solves the problem id love to relay it onto the dealer as they tried their hardest to get it fixed...(i had 12 loaners - most were average silverados but 2 Tahoes and an impalla lol)

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