2012 Chevrolet 2500 Suburban 4X4 fuel gauge problem

[tengrand2]

Hello. I have the 2 tank system totaling 39 gallons in my suburban. Recently the fuel gauge went to empty but the low fuel light was off. I needed to take a trip so I filled the tank, monitored my Fuel Used and I ran out at 26.5 gallons. AAA put some gas in and I went to fill it up and it only took 26 gallons. After the 750 mile trip the check engine light came on, Code P2066, Fuel Level Sensor B Performance. I cleared the code, started the truck and the gauge started working again, just for the day. What should I do first? This is a Florida truck and very clean underneath, not like my home state of NY. Today the gauge started working again so it obviously an intermittent problem. Thanks for your time!!

 

[Will L.]

Welcome.
Start by removing and cleaning the electrical connections including the ground wires.
After that you need to break out the multi meter or power probe and find where you are loosing signal. selector valve/ switch would be a good starting point. I don't have schematics to that so cant say for sure where else to look. Finding the schematics will save hours of guess work.. A common error is throwing parts at it hoping something fixes it- I strongly warn against this as it frequently adds cost and new problems that weren't there to begin with.

 

[MrMarty51]

X 2 on the grounds. Welcome to the forum TG.
A friend with His escalade, or whatever its called. Could not get it out of park. I told Him it sounds like a grounding issue. he hooked the code reader to it and it then was able to come out of park. I told Him that the code reader was a different source to ground. he took the wehicle to a shop, they tore it half ways apart then found the ground wire had come disconnected, I think it was in the council.
They fixed the ground wire and its been good to go for over two years now.

 

[tengrand2]

Welcome.
Start by removing and cleaning the electrical connections including the ground wires.
After that you need to break out the multi meter or power probe and find where you are loosing signal. selector valve/ switch would be a good starting point. I don't have schematics to that so cant say for sure where else to look. Finding the schematics will save hours of guess work.. A common error is throwing parts at it hoping something fixes it- I strongly warn against this as it frequently adds cost and new problems that weren't there to begin with.

Thanks for the info!

 

[tengrand2]

X 2 on the grounds. Welcome to the forum TG.
A friend with His escalade, or whatever its called. Could not get it out of park. I told Him it sounds like a grounding issue. he hooked the code reader to it and it then was able to come out of park. I told Him that the code reader was a different source to ground. he took the wehicle to a shop, they tore it half ways apart then found the ground wire had come disconnected, I think it was in the council.
They fixed the ground wire and its been good to go for over two years now.

Thanks for the info!

 

[THEFERMANATOR]

There is no selector valve in this system. It's 2 tanks, 1 filler, 1 gauge, 1 high pressure pump(front tank), and a transfer pump(rear tank). The ECM monitors the fuel level in both tanks, when it senses the front tank level dropping(to roughly 80%), it turns the transfer pump on in the rear(transfer/secondary) tank to transfer fuel to the front(primary) tank, when it senses the fuel level reaching roughly 90%, it turns the transfer pump off, and repeats this cycle until the rear tank is empty. All the while it is taking the reading from both tank senders, averaging it, and displays it on the fuel gauge.

If it senses anything outside of what it expects to see such as a sender being sporadic(poor connection at the contacts at the float or wiring), rear tank level not dropping when the transfer pump has been on, the front tank level going up when the transfer pump is off, or anything like this, it puts the fuel gauge to empty, and disables the transfer pump. So as you learned, you only have whats in the front tank when it senses a problem, the fuel in the rear tank will just be setting in the tank unuseable(you could manually power the transfer pump and move the fuel yourself that way in a pinch).

With the code you have, I would say you're getting an erratic/unexpected reading from the rear sender. These are systems that really require a scanner so you can see what the ECM is seeing. Be VERY careful back-probing the senders as these are wired directly to the ECM as sensor inputs(both wires go directly to the ECM). Put voltage to them and you can pop the 5 volt power supply in your ECM. You can try ohming out the wires to the rear sender from the ECM to the fuel module plug and removing the rear fuel module to ohm the sender as you move it through it's range to check for glitches/twitches. I would strongly suggest getting a bluetooth dongle or something and finding a decent obd2 app that can rear a 2012, and try and monitor the fuel level readings. Problem is these are normally specialized pids and not generic obd2.

 

[Will L.]

Cool. Sounds like a good design, just a bit to investigate when goofing up.

 

[tengrand2]

There is no selector valve in this system. It's 2 tanks, 1 filler, 1 gauge, 1 high pressure pump(front tank), and a transfer pump(rear tank). The ECM monitors the fuel level in both tanks, when it senses the front tank level dropping(to roughly 80%), it turns the transfer pump on in the rear(transfer/secondary) tank to transfer fuel to the front(primary) tank, when it senses the fuel level reaching roughly 90%, it turns the transfer pump off, and repeats this cycle until the rear tank is empty. All the while it is taking the reading from both tank senders, averaging it, and displays it on the fuel gauge.

If it senses anything outside of what it expects to see such as a sender being sporadic(poor connection at the contacts at the float or wiring), rear tank level not dropping when the transfer pump has been on, the front tank level going up when the transfer pump is off, or anything like this, it puts the fuel gauge to empty, and disables the transfer pump. So as you learned, you only have whats in the front tank when it senses a problem, the fuel in the rear tank will just be setting in the tank unuseable(you could manually power the transfer pump and move the fuel yourself that way in a pinch).

With the code you have, I would say you're getting an erratic/unexpected reading from the rear sender. These are systems that really require a scanner so you can see what the ECM is seeing. Be VERY careful back-probing the senders as these are wired directly to the ECM as sensor inputs(both wires go directly to the ECM). Put voltage to them and you can pop the 5 volt power supply in your ECM. You can try ohming out the wires to the rear sender from the ECM to the fuel module plug and removing the rear fuel module to ohm the sender as you move it through it's range to check for glitches/twitches. I would strongly suggest getting a bluetooth dongle or something and finding a decent obd2 app that can rear a 2012, and try and monitor the fuel level readings. Problem is these are normally specialized pids and not generic obd2.

Thanks for all the info!! One of these days I'll get to troubleshooting it.