FPCM is making my life miserable.

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04-09-2012
IDRIVEAG8GT

FPCM is making my life miserable.

Hey guys, here's another thread that concerns weird things that a GMT900 series pickup does. After the addition of my new fuel system I have been battling my FPCM, and the boost referenced regulator.

I'm running a twin Walbro 255 in tank fuel pump setup, one fuel pump being powered off the trucks fuel pump circuit, the other connected to a Kenne Bell BAP, which is triggered off of a Hobbs switch set to 3 psi boost.

Problem is, the regulator is set to 58psi then boost referenced off the manifold.

The FPCM however only knows low flow, normal, and high flow conditions. So I set normal and low flow to 53psi as that's where it idles at with vacuum on the manifold, and 72psi for high flow as that's 14psi boost.

Problem is, at mid boost levels the FPCM is commanding 72psi fuel pressure but delivered fuel pressure due to the regulator is only 66psi or so as it will only be boosting 8 psi which trips a CEL of the fuel rail pressure sensor going haywire.

How in the hell do you get around this problem? Is there a way to just disable the FPCM and let the primary pump run at 12 volts all the time without the CEL being tripped? I can't disable it in the tune :(
04-09-2012
DSteck

Unplug the FPCM, fix the codes, and power the pumps straight off the battery with a relay for ignition on power only.
04-09-2012
IDRIVEAG8GT

Quote:

Originally Posted by DSteck

Unplug the FPCM, fix the codes, and power the pumps straight off the battery with a relay for ignition on power only.

Even if I disable the FPCM, there's no way to turn off/get rid of the codes.
04-09-2012
DSteck

If you unplug it completely, sure there is. The module itself can't throw a code, and you'll just have loss of communication, which you can turn off.
04-09-2012
IDRIVEAG8GT

Hmm, I wonder if I can simply pull the FPCM fuse..... Then run the existing wires that power the fuel pump off the FPCM to the terminal stub on the fuse box.

Then that would leave the eliminate the need for the actual rail pressure sensor and all that other crap. :D
05-01-2012
ProTools4

Quote:

Originally Posted by IDRIVEAG8GT

Hmm, I wonder if I can simply pull the FPCM fuse..... Then run the existing wires that power the fuel pump off the FPCM to the terminal stub on the fuse box.

Then that would leave the eliminate the need for the actual rail pressure sensor and all that other crap. :D

how did it go?
05-02-2012
IDRIVEAG8GT

Quote:

Originally Posted by ProTools4

how did it go?

I'm actually still working on it now.
05-02-2012
vette_c6

keep us update after you finish ,,
05-02-2012
IDRIVEAG8GT

Quote:

Originally Posted by vette_c6

keep us update after you finish ,,

Well, I'm just trying to figure how to power the relay and keep everything under the hood civil. Motor is totally out right now as we lifted a head and blew a gasket at 22psi. :O

So needless to say, there is a mess of wires strung everywhere to sort through lol.
05-02-2012
smokeshow

Pins 85 and 86 power the relay.
05-03-2012
IDRIVEAG8GT

Quote:

Originally Posted by smokeshow

Pins 85 and 86 power the relay.

The actual fuel pump?
05-03-2012
smokeshow

I was being sarcastic haha. But yeah pretty much all relays use the same pins for the coil trigger.
05-03-2012
IDRIVEAG8GT

G'damn! :) that's useful to know.
05-04-2012
ProTools4

here is my controbution
:yay::yay::yay::yay::yay::yay::yay::yay::yay:
it is yet to go on the dyno
But it works on the rack
hope this helps someone
:yay::yay::yay::yay::yay::yay::yay::yay::yay:

test car
2010 Silverado 2-wheel drive 5.3
LSX376 w/ cogged 2300 Maggy
walbro 400 pump
AN send return fuel lines w/ rising rate adj return reg

process to delete FPCM with return fuel system
Unpluged the FPCM
*under the bed of the trucks above the spare
*passenger side rear seat under the quarter window on the 5thgen camaro
Large Pins 47 & 16 with around 10 gauge wire supply ground and power to the pump
ground is Pink ...WTF~! :bigshock:
Depin the connector and repin for new weather pack relay
Pin 13 Dark Green / white stripe is the trigger form the PCM key hot.

in HPT turn off P0230 and U0109

go make power! :drivin:
05-04-2012
IDRIVEAG8GT

Quote:

Originally Posted by ProTools4

here is my controbution
:yay::yay::yay::yay::yay::yay::yay::yay::yay:
it is yet to go on the dyno
But it works on the rack
hope this helps someone
:yay::yay::yay::yay::yay::yay::yay::yay::yay:

test car
2010 Silverado 2-wheel drive 5.3
LSX376 w/ cogged 2300 Maggy
walbro 400 pump
AN send return fuel lines w/ rising rate adj return reg

process to delete FPCM with return fuel system
Unpluged the FPCM
*under the bed of the trucks above the spare
*passenger side rear seat under the quarter window on the 5thgen camaro
Large Pins 47 & 16 with around 10 gauge wire supply ground and power to the pump
ground is Pink ...WTF~! :bigshock:
Depin the connector and repin for new weather pack relay
Pin 13 Dark Green / white stripe is the trigger form the PCM key hot.

in HPT turn off P0230 and U0109

go make power! :drivin:

:nohomohug:

But it's under the spare?! thats where that goofy bunch of wires went lol.
05-04-2012
IDRIVEAG8GT

And also, could you simply not cut the hot wire trigger for th FPCM then wire it to the power for the fuel pump. Wouldn't that eliminate the need for the relay? And then the FPCM fuse would simply act as the fuse for the fuel pump? Or am I thinking wrong here.
05-04-2012
smokeshow

Isn't your truck a 2007? Pretty sure 2007s in certain applications didn't have an FPCM, so it has to have the manual relay trigger. Pin 50 on the X1 ECM connector, DK GRN/WHT wire. That is what I am currently using until I can get my FPCM operational. Mines an 08 and still has the trigger, so you should be fine.
05-05-2012
IDRIVEAG8GT

Quote:

Originally Posted by smokeshow

Isn't your truck a 2007? Pretty sure 2007s in certain applications didn't have an FPCM, so it has to have the manual relay trigger. Pin 50 on the X1 ECM connector, DK GRN/WHT wire. That is what I am currently using until I can get my FPCM operational. Mines an 08 and still has the trigger, so you should be fine.

Nah mine is an 07 but it does have the FPCM voltage modulator
05-05-2012
GMjohn

If I remember correctly if you unplug the FPCM you have to jumper the GMLAN wires to keep the communications bus in tact. May cause other system issues if you leave the FPCM disconnected.

When you are done with the mods, disconnect the battery and measure pins 6 & 14 on the aldl. If they are 120 ohms and not 60 ohms you need to fix your can bus. (FPCM has passthrough communications)

John
05-08-2012
scooter k

I'm running a dual pump setup on an 08. I'm using the racetronix harness and relays to power the pumps. Also bought a transistor from ADM performance to use low voltage power from the ECM to trigger a low voltage relay which triggers the racetronix relay. Remove the fuse for the FPCM and tune on the communication codes. Works great. I've got a wiring diagram around here some where of how I wired everything. ADM has used the transistor in the past to defeat the FPCM on the 2010+ camaros.
05-08-2012
IDRIVEAG8GT

Mmmm, I took the easy way out on this one. Don't know if it will work yet or not but it should.

I simply cut the gray wire and ran another one to the misc ignition source in the fusebox with an additional circuit carrier and 30 AMP fuse. Pulled the FPCM fuse and it seems to be working well for now. No hot circuits or anything, no starting problems, and it's 58psi at key on. I turned the fuel pressure all the way up to 90 psi and held it for 2 minutes on a single pump with no issues. Will continue to test.
05-11-2012
ProTools4

Quote:

Originally Posted by ProTools4

process to delete FPCM with return fuel system
Unpluged the FPCM
*under the bed of the trucks above the spare
*passenger side rear seat under the quarter window on the 5thgen camaro
Large Pins 47 & 16 with around 10 gauge wire supply ground and power to the pump
ground is Pink ...WTF~! :bigshock:
Depin the connector and repin for new weather pack relay
Pin 13 Dark Green / white stripe is the trigger form the PCM key hot.
in HPT turn off P0230 and U0109

:yay::yay::yay::yay:
The relay FPCM delete worked great
truck dynoed great
customer has a big smile
life is good
:yay::yay::yay::yay:
06-30-2014
04colyZQ8

Will no fpcm cause a no start isue on a e67?
06-18-2017
mowton

1 Attachment(s)

Quote:

Originally Posted by ProTools4

here is my controbution

test car
2010 Silverado 2-wheel drive 5.3
LSX376 w/ cogged 2300 Maggy
walbro 400 pump
AN send return fuel lines w/ rising rate adj return reg

process to delete FPCM with return fuel system
Unpluged the FPCM
*under the bed of the trucks above the spare
*passenger side rear seat under the quarter window on the 5thgen camaro
Large Pins 47 & 16 with around 10 gauge wire supply ground and power to the pump
ground is Pink ...WTF~! :bigshock:
Depin the connector and repin for new weather pack relay
Pin 13 Dark Green / white stripe is the trigger form the PCM key hot.

in HPT turn off P0230 and U0109

go make power! :drivin:

Old thread but quick question, which pin (15 or 32) from the FPCM would you use to switch to pin 47 for pump power at the new Relay. Is pin 13 from the ecm enable on a low (gnd) or a high (+12v) and will it drive the relay direct?

thanks,

Ed M
06-19-2017
Rocko350

Quote:

Originally Posted by mowton

Old thread but quick question, which pin (15 or 32) from the FPCM would you use to switch to pin 47 for pump power at the new Relay. Is pin 13 from the ecm enable on a low (gnd) or a high (+12v) and will it drive the relay direct?

thanks,

Ed M

In running some diagnostics on other units with this FPCM, the pin 13 is a power signal from the ecm. Still unclear on exactly what it does that a communication signal couldn't do, or even the need for the UART on this module.

To answer though, I would put pin 32 to pin 47 and use pin 15 to drive the relay. That way the under hood power center sees everything as normal.

Chris
05-11-2021
Cody225

Thank you guys I really needed some of this info!
10-17-2022
HJR

Low fuel pressure issues

Quote:

Originally Posted by scooter k

I'm running a dual pump setup on an 08. I'm using the racetronix harness and relays to power the pumps. Also bought a transistor from ADM performance to use low voltage power from the ECM to trigger a low voltage relay which triggers the racetronix relay. Remove the fuse for the FPCM and tune on the communication codes. Works great. I've got a wiring diagram around here some where of how I wired everything. ADM has used the transistor in the past to defeat the FPCM on the 2010+ camaros.

Hi there I know this post is really old but I?m having trouble with my FPCM I recently purchased a racetronix harness and was wondering if you still had the wiring diagram for the same set up I have a 2008 Silverado with a walbro 450 fuel pump and throwing low fuel pressure. Any insight on what I need to do would be greatly appreciate it. Thank you so much in advance.