Fuel Gauge Pinned, Sending Unit Good

[Mattyp6]

Yeah with the new sender the gauge pins at E whether it's plugged in, with a resistor connected, or everything disconnected. I'm thinking though since the EVAP readiness monitor was satisfied, that it has to be the gauge. That's why I'm wondering what triggers the low fuel light, the gauge or the computer?

[j cAT]

Originally Posted by Mattyp6

Yeah with the new sender the gauge pins at E whether it's plugged in, with a resistor connected, or everything disconnected. I'm thinking though since the EVAP readiness monitor was satisfied, that it has to be the gauge. That's why I'm wondering what triggers the low fuel light, the gauge or the computer?

the computer .......gauge is a slave .. pcm is the boss !

the evap system does not use the sender. the in tank pressure sensor does the evap reporting to the computer.

[DeltaP]

Thanks J cAT and Tech II. Good info on testing. But it just struck me funny when Mattyp6 said " I just picked up a new gauge cluster from the junkyard".

[Mattyp6]

Originally Posted by j cAT

the computer .......gauge is a slave .. pcm is the boss !

the evap system does not use the sender. the in tank pressure sensor does the evap reporting to the computer.

The readiness monitor supposedly requires the fuel to be at a certain level, or it won't set. I could not get it to set with the old worn out sender that would never stay in the middle range (I tried for days), but with a new sender it was set and ready in just a few miles. This is what leads me to believe the computer (PCM, ECM, BCM, whichever it is) is getting a correct reading from the sender, and the problem lies beyond the computer (wiring to the cluster, or the cluster itself). Is there any way to see what the computer is reading for fuel level to verify any of this?

Originally Posted by DeltaP

Thanks J cAT and Tech II. Good info on testing. But it just struck me funny when Mattyp6 said " I just picked up a new gauge cluster from the junkyard".

Hah yeah, good point. It was so cheap compared to what I found online, that I had to grab it whether or not I need it. I'm sure it's just fine.

[j cAT]

Originally Posted by Mattyp6

The readiness monitor supposedly requires the fuel to be at a certain level, or it won't set. I could not get it to set with the old worn out sender that would never stay in the middle range (I tried for days), but with a new sender it was set and ready in just a few miles. This is what leads me to believe the computer (PCM, ECM, BCM, whichever it is) is getting a correct reading from the sender, and the problem lies beyond the computer (wiring to the cluster, or the cluster itself). Is there any way to see what the computer is reading for fuel level to verify any of this?


Hah yeah, good point. It was so cheap compared to what I found online, that I had to grab it whether or not I need it. I'm sure it's just fine.

the EVAP testing uses the pressure sensor in the tank. as far as the PCM completing this as a correct result that would be dependent on the fuel level. too low/high the resulting test would not be stored. so since the level is being reported as you say the pcm did store the EVAP system test. next would be the dash circuit .. so I would change that and see if with a different dash panel the gauge work

2003 was a bad year for dash indicators from GM vehicles.