SOLVED - 2014 Suburban Electrical gremlins

[bacon612]

Check out the note on circle at the top...

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Im unclear on what you are trying to show me here. I have a single battery.

 

[Doubeleive]

Couple things...

I bought an oem negative cable in the senseless pursuit of throwing money at parts to solve this issue. The delco negative cable comes with a new clamp sensor.

In my case, i found that the rvc system would only be disabled (or default as you say) when i disconnected the 2 pin from the alternator. When just disconnecting the clamp sensor, my voltage output was still high 14s and into 15s. Im now curious if theres a way to test the wire between the clamp sensor and the BCM (or wherever it goes). Would the clamp sensor throw a CEL if it was bad?

Interesting about the bad battery. When this issue began, i started by replacing my AGM (Costco) Iterstate battery that was a year old. I got a new Interstate AGM from costco. Same result. Then i swapped that for an Interstate Flooded (also from costco) and thats whats in there now. None of these swaps have shown me any progress in solving the issue. I did read, however, that generally speaking, you are suposed to replace batteries in these trucks with what came in them from factory. Which is flooded. Who knows...

Ive attached 3 screenshots below that have educated me about how the RVC system operates
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one thing to keep in mind is that by default upon startup the charging system will command higher output from the alternator for the first *** seconds to re-juice the battery from starting, so 14-15v in this case is normal for like the first minute or so. then it drops down to normal requested voltage.
unplugging the 2-pin alternator is basically turning off the alternator, the signal is digital, no signal-no charging
unplugging the rvc sensor does not throw a code, but it may show a error somewhere in the tech2 data I believe I saw it in there somewhere when I was ballz deep in the issue but that 4+ years ago.
unplugging the rvc sensor should make it default to 13.4v or around there, but this may be dependent upon the battery state of charge and battery temperature and draw.

if you have a tech2 you can go into the charging system and see what mode it is in and all the relevant data it should show something like economy mode=true/false, or not commanded, something to that effect. it should also show the draw and what is being commanded versus what is it actually doing.

during all my troubleshooting I had also replaced my ground cable and the sensor, but determined at some point that it was not my problem at all. I replaced the battery and re-tested the charging system with the tech2 and everything was working normal again and haven't looked at it since.


the problem the bad battery created was the draw was more voltage/amps than the alternator was providing because the battery was saying hey it's all ok, but the actual draw was more than the alternator was putting out so it would drop to like 11v and be in economy mode when it should have been making 14v+

if you have wipers on full speed, seat heaters, headlights on, flashers on, radio, defrost on. all at the same time it sure as heck should not be in economy mode

 

[bacon612]

one thing to keep in mind is that by default upon startup the charging system will command higher output from the alternator for the first *** seconds to re-juice the battery from starting, so 14-15v in this case is normal for like the first minute or so. then it drops down to normal requested voltage.
unplugging the 2-pin alternator is basically turning off the alternator, the signal is digital, no signal-no charging
unplugging the rvc sensor does not throw a code, but it may show a error somewhere in the tech2 data I believe I saw it in there somewhere when I was ballz deep in the issue but that 4+ years ago.
unplugging the rvc sensor should make it default to 13.4v or around there, but this may be dependent upon the battery state of charge and battery temperature and draw.

if you have a tech2 you can go into the charging system and see what mode it is in and all the relevant data it should show something like economy mode=true/false, or not commanded, something to that effect. it should also show the draw and what is being commanded versus what is it actually doing.

during all my troubleshooting I had also replaced my ground cable and the sensor, but determined at some point that it was not my problem at all. I replaced the battery and re-tested the charging system with the tech2 and everything was working normal again and haven't looked at it since.


the problem the bad battery created was the draw was more voltage/amps than the alternator was providing because the battery was saying hey it's all ok, but the actual draw was more than the alternator was putting out so it would drop to like 11v and be in economy mode when it should have been making 14v+

if you have wipers on full speed, seat heaters, headlights on, flashers on, radio, defrost on. all at the same time it sure as heck should not be in economy mode

Thanks for the insight. Are you aware of a way to test the clamp sensor? Where does that wire go?

As an aside, what kind of battery are you running?

 

[Doubeleive]

Thanks for the insight. Are you aware of a way to test the clamp sensor? Where does that wire go?

As an aside, what kind of battery are you running?

the wire probably goes to the bcm but not sure to be honest @mikez71 probably has a diagram
I am running dual interstate agm's in parallel which are around 4 1/2 years old now, I expect they are at the end of there rope soon the cali heat kills batteries

 

[solli5pack]

Thanks for the insight. Are you aware of a way to test the clamp sensor? Where does that wire go?

As an aside, what kind of battery are you running?

I was wondering where do the wires from the little connector on the back of the alternator go? Are they definitely a component of the RVC system?

 

[mikez71]

I believe the ECM and BCM both can change alternator output.
BCM maybe economy adjustments while the ECM can boost voltage when required. (Unless you unplug the alternator 2-wire plug)

 

[Doubeleive]

for whatever it's worth also
mechman sells a little device that you plug the 2 pin connector into, then you can run a old school 4 pin alternator with just a 12v turn on signal.
bypasses the whole mess

 

[mikez71]

Im unclear on what you are trying to show me here. I have a single battery.

Only that there is a fuel economy mode, and it is tied to the current sensor.
(And that they were considering dropping that mode for dual batts.. why?)

It's just me, I find stupid things interesting..

 

[mikez71]

I was wondering where do the wires from the little connector on the back of the alternator go? Are they definitely a component of the RVC system?

 

[bacon612]

for whatever it's worth also
mechman sells a little device that you plug the 2 pin connector into, then you can run a old school 4 pin alternator with just a 12v turn on signal.
bypasses the whole mess

I saw that. If I have to live with not knowing what is causing my issue when everything is plugged in as intended, I will go this route. It'd still be nice to know what is causing my issue, though.

 

[bacon612]

Only that there is a fuel economy mode, and it is tied to the current sensor.
(And that they were considering dropping that mode for dual batts.. why?)

It's just me, I find stupid things interesting..

I understand what you were trying to say now

 

[Doubeleive]

I saw that. If I have to live with not knowing what is causing my issue when everything is plugged in as intended, I will go this route. It'd still be nice to know what is causing my issue, though.

I didn't know they had it until well after I had bought there $400 2-pin alternator

 

[bacon612]

I didn't know they had it until well after I had bought there $400 2-pin alternator

Interesting. So you are using one of these mechman alternators. I have had 3 of the OEM Delco alternators in my truck including the factory one that had ~125k miles on it. A part of me wonders if maybe whatever talks to the RVC system isnt calibrated properly. The two new Delco alternators ive had in the truck were ordered from SummitRacing (where i also see the mechman units sold for $$$). Summit sells a Bosch reman unit thats also 160 amp just like the delco i am using. In my deep reading, Bosch is the company responsible for this delco RVC design. Almost curious to try a different alternator and see if it makes any difference.

I am also thinking that its probably time to get a tech2. Anyone have opinions of a decent model they'd recommend?

 

[Doubeleive]

Interesting. So you are using one of these mechman alternators. I have had 3 of the OEM Delco alternators in my truck including the factory one that had ~125k miles on it. A part of me wonders if maybe whatever talks to the RVC system isnt calibrated properly. The two new Delco alternators ive had in the truck were ordered from SummitRacing (where i also see the mechman units sold for $$$). Summit sells a Bosch reman unit thats also 160 amp just like the delco i am using. In my deep reading, Bosch is the company responsible for this delco RVC design. Almost curious to try a different alternator and see if it makes any difference.

I am also thinking that its probably time to get a tech2. Anyone have opinions of a decent model they'd recommend?

I ended up buying the mechman because I had bought a couple other higher-amperage units and they failed within a short period the mechman has held up fine.
the newer 2015+ gm ac delco alternators are the same design as the mechman with pressed diode's
this one is probably the safest bet as you are covered by ebay if it fails to arrive or is doa

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[solli5pack]

Dropped the dome light. Everything looks new in there.

I did, however, find something curious. If i disconnect the 2 pin connector on the alternator (which i think is the RVC system) Amperage with my mulitmeter reads a rock steady 13.6V. No surging headlights or interior lights. Rock solid. Why?

While i could just keep the 2 wire connector off of the alternator and put up with reasonable voltage with no fluctuations with a 'fix charging system' warninig light, I'd much rather know why the RVC system is causing my problem....

Any thoughts out there?

So I had some residual flickering with the Yukon after cleaning all the corrosion. Went out and pulled the two pin connector and lights are rock solid. Not a single flicker. Also no Check engine light yet with the connector unplugged. Thanks to @mikez71 diagram looks like it runs right to the ECM. Leaving it unplugged and we'll see what.happens. More research to do on RVC....RVC delete?

 

[mikez71]

Maybe bad sensor? bad connection?
keep us updated!

 

[bacon612]

I think my next steps are to test the charging system based on some images i found on another thread. I just need to get a tech II first.

 

[solli5pack]

I had to plug it back in this morning. Voltage dropped below 12 volts when I started it up according to the dash gauge. The engine definitely idles differently when the plug is plugged in. At least we have something to chase now.

 

[mikez71]

You are talking about the alternator plug, not the rvc sensor right?

Because, I thought it was odd that the bacon612's alt defaulted to 13.6V..
which is the stock initialization duty cycle of 60%=13.8V
But I thought the alternator needed that signal really..

 

[Doubeleive]

So I had some residual flickering with the Yukon after cleaning all the corrosion. Went out and pulled the two pin connector and lights are rock solid. Not a single flicker. Also no Check engine light yet with the connector unplugged. Thanks to @mikez71 diagram looks like it runs right to the ECM. Leaving it unplugged and we'll see what.happens. More research to do on RVC....RVC delete?

Might want to post on your original thread in order to prevent confusion here.......