Hooking up 97 fuel gauge to 12200411 PCM

[AK49BWL]

I started messing around with this a little this evening, got the PCM reading the fuel level sender and outputting PWM to the gauge. The only "problem" at the moment is that the PCM "Gauge Output" and the "Primary Volume" tables are completely not calibrated for the truck with several write operations, I was able to get the gauge output high point and low point set near perfect buuut, now I have to get everything in between. Anyone else done this with their 0411 swap, and possibly have a working Primary Volume and Gauge Output table I can use? I run HPTuners so that would be easiest to work with. If not, that's cool - I'll get mine set up over time and post back my settings

Fuel Tank Level Sensor, purple wire runs from under the truck, up to the firewall right behind the fuse box in the engine bay. There's a harness connector hiding under the brake booster that's a real pain to get to, but unhooking it makes the wires a lot easier to deal with. I cut the purple wire, ran the tank side to the PCM Red connector C2 - Pin 54 and the gauge side to Red C2 - Pin 38. Set up just like an 02 Express! But the Express calibration isn't quite right for my truck lol.

 

[Kingjames]

Did

I started messing around with this a little this evening, got the PCM reading the fuel level sender and outputting PWM to the gauge. The only "problem" at the moment is that the PCM "Gauge Output" and the "Primary Volume" tables are completely not calibrated for the truck with several write operations, I was able to get the gauge output high point and low point set near perfect buuut, now I have to get everything in between. Anyone else done this with their 0411 swap, and possibly have a working Primary Volume and Gauge Output table I can use? I run HPTuners so that would be easiest to work with. If not, that's cool - I'll get mine set up over time and post back my settings

Fuel Tank Level Sensor, purple wire runs from under the truck, up to the firewall right behind the fuse box in the engine bay. There's a harness connector hiding under the brake booster that's a real pain to get to, but unhooking it makes the wires a lot easier to deal with. I cut the purple wire, ran the tank side to the PCM Red connector C2 - Pin 54 and the gauge side to Red C2 - Pin 38. Set up just like an 02 Express! But the Express calibration isn't quite right for my truck lol.

 

[Kingjames]

Did you ever find a fix for this issue I'm having the same problem

 

[AK49BWL]

There was never really a "problem" per-se - I just had to find the right values to program my PCM with to get proper gauge output. And yeah, I did that.

 

[Supercharged111]

Why did you bother at all? I thought pre-98 had the sensor going directly to the gauge.

 

[AK49BWL]

Why did you bother at all? I thought pre-98 had the sensor going directly to the gauge.

It does. Which means every time you hit the brakes, the gauge shoots to empty. It doesn't do that when routed through the PCM. Plus I have control in the tune over where the gauge shows in relation to actual fuel level.

 

[Supercharged111]

I don't get it. My 97 doesn't shoot to empty when I hit the brakes. Still has black box.

 

[AK49BWL]

it doesn't do it when the tank is full or so, but below about the 3/4 mark, when stopping from 45+ mph to a red light or something, my gauge would drop significantly until I came to a stop, then it'd sit there and sorta go back and forth for a bit while the fuel sloshed in the tank. Since I hooked it up to the PCM, I was able to read the sending unit voltage, and while coming to a stop, the voltage drops, then bounces for a bit, but the gauge output remains steady because the PCM regulates that.

 

[AK49BWL]

Also thought of another reason to do this, thanks to a comment on one of my videos: For those who may want to put a Blazer DIC in their 96-97 upper console, hooking the fuel gauge and sender to the PCM will enable the DIC to show you remaining fuel mileage. Without the sender hooked up, this would never work. It also gives the user control of the gauge-to-actual fuel in tank ratio, if you have a tuner. You set where the gauge goes at whatever fuel level, rather than it being based on arbitrary values set from the factory which never seem to be correct.

 

[AK49BWL]

Just gonna leave this here in case anyone else wants to do this, or ends up with a 98+ Vortec swap on an earlier truck.

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Those sender values will get you into the right ballpark, but I will be the first to admit they're not perfect, and I haven't really bothered trying to get them perfect.... Your gauge will show empty when you have about 4-5 gallons left, but from full to half-tank, isn't too far off.

On the other hand, I spent several hours getting the gauge output PWM table right, so that one SHOULD be just about perfect.