Fuel pump wiring

[Dropped88]

Pcm has complete control over gauge I dealt with all that with my ls swap


Id bet a segment swap in tune for a single tank would fix it. But id have to look at wiring diagrams and compare the 2 systems

 

[mitten400]

Pcm has complete control over gauge I dealt with all that with my ls swap


Id bet a segment swap in tune for a single tank would fix it. But id have to look at wiring diagrams and compare the 2 systems

Sorry, that is beyond my knowledge. Any further help would be appreciated though. Is it possible that I could bypass the pcm?

 

[AK49BWL]

The wiring is very similar to the PCM between the two: the balance module takes care of differentiating the two tanks and sends a single output to the PCM representing overall fuel level. Compared to later trucks with the LS PCMs that actually had two separate senders and inputs on the PCM for each.


Bypassing the PCM in your case would not work at all due to the difference in sender resistance. The gauge will only work with 0-90 senders, or PCM PWM. Your only option there would be to swap to the 97-older sender, but that also deletes the fuel tank pressure sensor that the 98+ uses.

 

[mitten400]

The wiring is very similar to the PCM between the two: the balance module takes care of differentiating the two tanks and sends a single output to the PCM representing overall fuel level. Compared to later trucks with the LS PCMs that actually had two separate senders and inputs on the PCM for each.


Bypassing the PCM in your case would not work at all due to the difference in sender resistance. The gauge will only work with 0-90 senders, or PCM PWM. Your only option there would be to swap to the 97-older sender, but that also deletes the fuel tank pressure sensor that the 98+ uses.

That was my next question. I was thinking if I bypassed the pcm I would change to a 0-90 unit. Is the fuel tank pressure sensor the other 3 prong receiver on top of the pump?

 

[AK49BWL]

That was my next question. I was thinking if I bypassed the pcm I would change to a 0-90 unit. Is the fuel tank pressure sensor the other 3 prong receiver on top of the pump?

Yep

 

[Dropped88]

The wiring is very similar to the PCM between the two: the balance module takes care of differentiating the two tanks and sends a single output to the PCM representing overall fuel level. Compared to later trucks with the LS PCMs that actually had two separate senders and inputs on the PCM for each.


Bypassing the PCM in your case would not work at all due to the difference in sender resistance. The gauge will only work with 0-90 senders, or PCM PWM. Your only option there would be to swap to the 97-older sender, but that also deletes the fuel tank pressure sensor that the 98+ uses.

Thanks never looked that hard into may change unit on mine. I have full to half. But half to empty is still ***** haha

 

[mitten400]

Okay, I picked up a 1996 sending unit (brand new, 0-90ohms). I tested both sending units and checked for ohms at the pin for the cluster bracket. On both sending units, no matter what float position, it always read low 40's. So I know i my problem is before the gauge now. I'm at a loss. It's like the pcm thinks its pegged at empty and its using the 40-250 scale. Yesterday I was able to get 200 ohms at the pin. Is this a sign of an open ground?

 

[Dually From Hell]

98+ fuel gauge gets its reading from pcm.

So sending unit to pcm to cluster

And its a PWM signal

Hi have to chime in on this since I'm having a similar issue.. i too have a 98 k3500 my fuel gauge is pegged full. I've replaced cluster it may be a 97 and replaced sender and still same. Now about what u wrote about the 98 getting reading from pcm I have a 97 pcm and wire harness in my 98. The original was cut up into pieces.. do u think that has anything to do with my pegged gauge?

 

[454cid]

Hi have to chime in on this since I'm having a similar issue.. i too have a 98 k3500 my fuel gauge is pegged full. I've replaced cluster it may be a 97 and replaced sender and still same. Now about what u wrote about the 98 getting reading from pcm I have a 97 pcm and wire harness in my 98. The original was cut up into pieces.. do u think that has anything to do with my pegged gauge?

The resistance changed at some point, but I dont recall the year. I tested my sender before I installed it in the new fuel tank.