By sensor, do you mean the sending unit shown in post #6?


Where is the rheostat located? Can the old rheostat be replaced with the newer version as well?

 

Correct, post 6. De-soldered the new and replaced with the original one that was confirmed to work prior to the FP going out. The new one was throwing error codes that were the fuel level sensor so I removed the tank again and replaced with the old fuel level sensor. All codes went away but now, only half on the gauge. Everything with the fuel system is now exactly as it was prior to the FP failure other than a new FP.

 

just tune the codes out and be done with it. the fuel gauge will return to function properly.

 

OK now I'm confused.
I'm reading this thread because my fuel gauge intermittently stops working and throws an error on the DIC. I only works when the fuel is at about 3/4 full and fails on fill up or when below 3/4 to 1/2 tank. So I think both fuel tank sending units have failed, but my fuel pumps are fine.

So now the new sending unit is not compatible with the existing rheostat? What parts do I need to get my gauge working again?

 

That sound like the fuel level sensor in the passenger tank may be faulty. The resistance level changes as the float moves up and down, lower fuel, lower resistance if I remember correctly. The brushes on my NEW level weren’t making constant contact as it “swept” along the contacts, which originally gave me a fuel system error.

 

The "sending unit" and the "rheostat" are the same thing. It's just a variable resistor with a float arm on one side and two wires hanging out the other. There's one inside each gas tank.

It sounds like your right (passenger) side level sender is shot. Pull codes to confirm.

You need the sending unit that goes with your model year. In 2007 GM reversed the resistance range of the level sensors. According to your profile, your car is a 2010, so you'd use the later style.

 

Ah! Thanks. I was confused by DSOMC6's comment about the "newer fuel level sensor isn't compatible with the older rheostat. You either have to reuse the older rheostat, or change the calibration settings."

Yes, my car is a 2010.

The code is P2068 "Fuel Level Sensor B Ckt High"

I figure I probably should change the sensors in both tanks. The gauge still fails even if it's below 1/2 full.

 

The fuel gauge will remain disabled as long as P2068 is set. If your left sensor was bad, you'd have more codes.

That said, I agree you should change both sensors.

 

Not necessarily. Between full and 1/2 it works intermittently, even with the code set and the check engine light on. Below 1/2 it doesn't seem to work at all.

 

Yes you're right: I checked the service manual and the P2067 and P2068 cause the gauge to "read inaccurately" whereas P2066 and P2636 cause the gauge to "default to empty."

Either way, if the left sensor was off-scale low or high you'd get another code. To be providing a valid empty signal it would have to be parked right at 250 ohms, which is unlikely unless it were physically stuck, which it probably isn't. But I'd change it anyway.

 

Thanks for the info.

 

I have an A&A centrifugal supercharger installed in a base 06. The supercharger needs a higher fuel flow than the base fuel pump delivers. One solution is to install a Z06 fuel pump. However to keep installation costs down, the A&A installation comes with a voltage amplifier to achieve higher fuel flows from the base pump by driving it at a slightly higher than normal voltage. A question is, even if you don't have a supercharger......just the base engine......maybe you might want to install a Z06 pump? Sort of a just in case thing?

 

Stock pump is completely adequate for a stock engine. There's nothing to gain by changing it. However, using the Z06 pump won't hurt anything either.

 

If there's a need: I have a stock hat with a Walbro Hellcat 450 pump mounted in it; both tanks, w/crossover tube (and the all important O rings) that I would let go. 24K mile 2012, This setup is not a year old. Have not removed the hat from the tanks (which is the hard part). Went to custom tank and external pump. Car has a 4Link/9". PM me.

 

I just replaced my fuel pump on my 2008 M6 coupe and this thread was invaluable. Since its a sticky and these cars are getting older, I thought I'd add a few problems to the mix:

just as a frame of reference, I live on a dirt road in the Mojave desert and the pump died at 136k miles. Ive owned this car since new and its my daily driver. I also have Z06 exhaust, so the bigger tubes added a bit more trouble for access. That said:

- Plan on buying a supply of the plastic wishbone clips for the fuel line disconnects. Mine were brittle, and I broke a few during the process. A run to the auto parts store found them out of stock and "had to be ordered".

- When I got the main crossover tube separated and the LH tank coming down, the inner plastic tubes were still connected fairly firmly. Despite them being a simply slip fit, It took quite a bit of effort to get them to release.

- The vent tube above the crossover tube was also hard stuck together. Even with the wishbone lock completely removed, it still took a fair amound of force to twist/pull the coupler apart.

- The "snap in/out" C bracket over the trans would not allow the crossover to release. The tube had to be moved so far that it actually created more tension (length wise) and it would just snap right back in. I had to take the nut off the bracket and drop it off the stud.

- When you inspect the new fuel pump, look closely at the snap locking tab that holds the float switch in place. Mine was bent, and did not catch the sender at all. It was essentially free to slide up and down the mounting rails. I fixed mine by drilling a tiny hole through the sender and mount rail, then securing it with a loop of .020 stainless steel lockwire.

 

That was the toughest part of doing mine, and I had no idea what was stuck at the time so it was a total PITA to try to figure out why it wouldn't come down

 

I first put this thread together way back in November of 2010! No doubt people have gotten good use out of it and there are new techniques and “discoveries” popping up all of the time as these cars age. Keep the knowledge contributions coming.

 

Thanks for this thread OP, I just did both of my sender units and it was truly a PITA. Took me approximately 12 hours on my 2007 M6. Ordered the parts from partsgeek.

The hardest part was removing the crossover tube since the inner tubes where really stuck.

What I’ve learned is that you might have to apply an inhuman amount of force to pull out the crossover tube. Make sure the applied force is horizontal. If you end up breaking the tabs inside the crossover tube that secure the inner tubes, use zip ties to secure them back.

Also as you mentioned, my fuel pump had swollen. I ended up separating the bottom part of the fuel pump using the 3 tabs. Then the top part of the FP comes out easily, and the bottom part of the FP can be fished out using screwdrivers through each of the 3 tab to pull.

 

Motorhead-47, i am hoping you are still around.
I am looking for specific feedback and/or advise related to the P2066 & P2068 codes for the fuel sender circuit. I would like to hook up external jumper the wires to new replacement fuel senders for testing before going thru the extensive process required to replace the fuel senders in the tanks.

To do this, I am in need of a snapshot of the fuel sender schematic to help determine which two of the three wires coming out of the fuel sending unit plug are used for the sending unit side of the circuit. I would be greatly appreciative of any information explaining/showing the color of the two wires used for the sender side of the circuit. I would like to confirm this before is do something wrong and toast a control board....LOL

 

On the drivers side it's the 2 center wires on the connector. The outside wires are + & return. I'm not sure on the passenger side.

I just installed a Fore fuel system in a automatic without pulling the drivetrain. I found if you go ahead and buy both in-tank fuel lines and a new crossover tube (Rockauto ~ $200) it's make the job 10x faster and easier. When you disconnect the crossover tube the in-tank lines normally get stuck together. Just reach up there with a pair of dikes and cut it then the tank will drop right out. Same on the passenger side. While you were disconnecting the crossover tube you end up stretching it out so the new one will be about 1.5 inches shorter making it easy to reinstall.