Hooking up 97 fuel gauge to 12200411 PCM

[LovesDunes]

Second option is true. God, I can't imagine the uproar if you had to pay $100 every time you wanted to make a slight change

That is exactly what I thought you were going to say. HaHaHa

I figured that is the reason the tuner guys in my area were charging so much. I found a guy on Craigslist to make the changes to the ECU to get the Tahoe running and he has been awesome, but he is not close anymore.

 

[LovesDunes]

In your first post you mentioned cutting the purple wire the passes through plug C104 and running the tank side to the PCM Red connector C2-54 and the gauge side to C2-38. I know those two spots are currently empty on my red connector. I'll try that when I get home.

I'm also supposed to check C2-64 (Dark Green Wire) and C1-23 (Black Wire). Both of those wires are listed as Low Reference for Fuel Gauge and Fuel Tank Pressure Sensor.

I'm pretty sure I have the correct wires for C2-64 and C1-23, but I am positive I don't have anything in C2-54 and C2-38.

 

[AK49BWL]

I'm not sure on the low refs. On mine the pump and sender are together grounded to the engine. The pin numbers for the low refs check out tho. You could use C1-21, 23, 49, 50, 53, 54, 60, 61, 63, and C2-20, 23, 57, 60, 61 for any ground/low ref (which is just ground by a different name lol). The end pins (C1 and C2 1, 40, 41, and 80) are connected to ground, and internally connected to all of those pins listed above. Alternatively, any sensor's "low ref" could be directly grounded to the engine. The effect is the same.

 

[LovesDunes]

I always wondered about that. When I was rebuilding the harness to move the computer and under hood fuse box to the center console area I know I changed a lot of the grounding locations. I ran ground straps from the engine to frame, engine to body and body to frame. So far everything but the fuel gauge is working great. It was quite a job, but when I pop the hood it's so nice under there.

 

[LovesDunes]

I finally stopped cruising around in the Tahoe long enough to rewire the purple wire from the fuel level sending unit to pass through the ECU. Unfortunately nothing changed.

Are there setting in HP Tuners that might resolve this?

I'm wondering if the gauge cluster from a 98 or 99 would fix the problem?

 

[AK49BWL]

Possible the toggle "Gauge uses PWM" is turned off. The gauges themselves are all the same for all 95+ GMT400 trucks so swapping clusters will NOT fix it.

 

[LovesDunes]

Possible the toggle "Gauge uses PWM" is turned off. The gauges themselves are all the same for all 95+ GMT400 trucks so swapping clusters will NOT fix it.

Really? I thought that because the ohms on the newer fuel level sending unit is different, the fuel gauge would be different on the newer OBS dash.

Oh well, just another reason to get HP Tuners sooner than later.

This will probably take some time to get sorted out, but I'll be sure to come back with the fix in case anyone else is dealing with this stuff.

 

[AK49BWL]

Really? I thought that because the ohms on the newer fuel level sending unit is different, the fuel gauge would be different on the newer OBS dash.

The PCM converts the newer signal to the gauge-readable older signal. You could put a 94 cluster in a 99 truck and it would still read correctly.

 

[LovesDunes]

The PCM converts the newer signal to the gauge-readable older signal. You could put a 94 cluster in a 99 truck and it would still read correctly.

That's good to know.

Can HP Tuners scan my Tahoe for codes and clear the CEL? I went to leave for AZ today and all of the sudden the CEL is on and flashing and it feels like it's running on 6 cylinders.

 

[Supercharged111]

That's good to know.

Can HP Tuners scan my Tahoe for codes and clear the CEL? I went to leave for AZ today and all of the sudden the CEL is on and flashing and it feels like it's running on 6 cylinders.

Clearing codes won't fix a misfire.