Hooking up 97 fuel gauge to 12200411 PCM

[Supercharged111]

Hi. I recently finished the LS swap on our 97 Tahoe. Runs awesome, but the gas gauge reads way beyond full.

I swapped the 97 in-tank fuel pump / sending unit out for a 99 unit because I needed Fuel Tank Pressure Sensor. I am pretty sure the Ohms on the newer sending unit is different than the 97.

Do you think the HP Tuners program will help get the gauge working correctly, or will I need to address the Ohms thing first?

Was your 97 the new or old style sender? I 411 swapped my dually which was the old style sender and the gas gauge was unaffected because the tank still runs the gauge.

 

[AK49BWL]

You know, I forgot about that bit. And that being the case, unless the sender wire was routed to the PCM during the swap, that should still be the case.... Meaning not only would you have to change the sender values in the tune, but you'd also have to add two wires to your PCM lol - one for the sender, and one for the gauge. Unfortunately you can't change the gauge itself to read the 40-250 sender properly.

 

[Supercharged111]

You know, I forgot about that bit. And that being the case, unless the sender wire was routed to the PCM during the swap, that should still be the case.... Meaning not only would you have to change the sender values in the tune, but you'd also have to add two wires to your PCM lol - one for the sender, and one for the gauge. Unfortunately you can't change the gauge itself to read the 40-250 sender properly.

I forgot to mention I swapped an Escalade cluster into the dually as well and it still all works fine. And I sawpped that cluster into my 98 flipper dually with a 99 PCM and that one works fine too. So I'm really failing to see where LovesDunes is having any sort of trouble here.

 

[AK49BWL]

Because the gauges are the same in all of the trucks. The PCM has control of the gauge in the 98+ trucks, which is how they got away with changing the senders in the 98+ trucks. The PCM is essentially converting the 40-250 sender values into the gauge-displayable 0-90 values. You plug a 40-250 sender into a 0-90 gauge directly, it's gonna read over full until you're actually nearly empty.

 

[Supercharged111]

Because the gauges are the same in all of the trucks. The PCM has control of the gauge in the 98+ trucks, which is how they got away with changing the senders in the 98+ trucks. The PCM is essentially converting the 40-250 sender values into the gauge-displayable 0-90 values. You plug a 40-250 sender into a 0-90 gauge directly, it's gonna read over full until you're actually nearly empty.

That begs the question, did he change the wiring? Or did the donor have a different size fuel tank for which the PCM is still programmed?

 

[AK49BWL]

It is possible the sender values already programmed may work fine. My guess is, his sender is still routing directly to the gauge tho.

 

[Supercharged111]

It is possible the sender values already programmed may work fine. My guess is, his sender is still routing directly to the gauge tho.

In which case there should be no issue which is what makes this all the more weird.

 

[AK49BWL]

The fact that he's using a 40-250 sender wired directly to the gauge that expects 0-90 senders and it doesn't work right is weird?

 

[Supercharged111]

The fact that he's using a 40-250 sender wired directly to the gauge that expects 0-90 senders isn't weird?

I had that backwards, didn't I? His tank never fed the gauge in the first place. Since this is more than a 411 swap I can see how this could come to be. What's more, he may get a jumpy gauge if he lets the PCM control the gauge.

 

[AK49BWL]

It's a 97 Tahoe, yes, it did run direct lol. He even mentioned that he swapped to a later sender for the tank pressure sensor that the trucks up to 97 didn't have, indicating he used to have a 0-90 sender, and now it's a 40-250, which means his gauge is going to read over full until he gets down to about 1/4 tank, and the gauge will NEVER read less than 1/2. If he wants the gauge to work right, he's going to have to run the sender line to the PCM and let the PCM control the gauge. Only way it will EVER work right.

Also mine has been under PCM control since I STARTED this thread and has never been jumpy in the slightest, not even when I swapped to an Escalade cluster myself. So yeah

@LovesDunes did your LS swap go in with a 12200411 PCM or some other: P01 with the Blue/Red or P59 with the Blue/Green connectors? I ask because some of the P59 PCMs don't have the drivers for the fuel gauge PWM circuit and won't work with the analog gauge at all - in which case you may be entirely out of luck without an aftermarket gauge.