fuel pump not working, and my head is scratching.

spankrz · July 31, 2013

my truck is a 07 nnbs silverado 1500 extended cab 6.5' bed 4x4 5.3 engine vin "j", almost 170,000 miles.

a couple of weeks ago check engine light came on, "lost communication with fuel pump" or something along those lines. cleared the code, light was back on within a few minutes. truck still ran as it should.

this morning, got in the truck to get some work done and it would not start. fuel guage still worked. starter would enguage and engine would turn over as it should, but would continue to do so without starting. tried turning key on and off several times to build up pressure, no luck there either.

-fuel pump fuse is fine checked with multimeter

-fuel pump relay is fine via swapping with an identical relay.

---pulled off bed---

-installed new fuel pump from carquest, no change. wiring connections looked clean and not burned. fuel guage works as it should.

---called local dealer. they recomended fuel pump control module (located above spare tire)---

-installed new gm fuel pump control module. no change.

---with my hand on top of the fuel pump and someone turning the key to the "run" position, i can fell that it does nothing at all when it should prime.---

sorry for the long post, just wanted to provide any details that someone may ask. i really hope it is not a wiring problem, as i would hate to cut up the nice neat factory harness to check for faulty wiring unless i absolutely have to.

ANY help or input would be appreciated. feel free to ask any questions, i usually wind up looking over the stupid simple things...

gmtech4 · August 10, 2013

awesome !!! yw

gmtech4 · May 25, 2014

sounds about right ,,,

we (army shop) bought a tech 2 from our hillbilly local dealer ,they handed it over to the army guy and we plug it in and nothing ,,,,,i said "did ya get it filled with software"? ,,,

i said ,,,take it back and have them put stuff in it ,,,,they let it go empty ,i couldnt believe it lol

TJMaine · May 27, 2014

Sheneeda rides again! Picked up from dealer today after programming the Fuel Pump Flow Control Unit! Runs like new!

scooby5121 · August 1, 2013

i would look into the "lost communication with fuel pump"

error code you originally got with the dealer before pursuing any further with it.

It may be the cheapest way for a True Fix...

Scooby

Fla Eagle · June 1, 2015

Hhhmmmm. Interesting. My 07 has 170k and I am having issues as well. Only have 42psi at the rails so I replaced the pump. Same issue except I log this time and every 20 pressure jumps to 70 psi and back down to 42-45. Im thinking it may be FPCM as well. Sucks I replaced the pump for no reason.

scooby5121 · August 1, 2013

Well if you have a 200 to 2007 old body style Chevy or GMC truck you may
get that annoying abs and sometimes the fuel pump that won’t work. This
is a common issue and usually just a bad ground on the driver-side
frame just under the drivers door by the body mount. Simple repair just
unbolt these grounds and sand the frame where they make contact clean
the terminal as well. I would use 80 grit sandpaper to do this when you
got them clean just bolt them back up make sure they are tight and can’t
be moved by hand. Hope this one helps you out you can do this without
spending a dime.

Quotted from A gm site.

Scooby

gmtech4 · August 1, 2013

i would look into the "lost communication with fuel pump"

error code you originally got with the dealer before pursuing any further with it.

It may be the cheapest way for a True Fix...

Scooby

^^^^^^^^^^^^^^^ +100 ,stop the shot guning of parts(i think you have at this point) ,,,,,,did ya have the FPCM programmed ?or did someone tell you its plug and play ?let me know ,i can look it up for you if ya want,,,

i believe ya looked past the computor controlled truck thing,,,good luck

spankrz · August 1, 2013

mine is the new body, it is the truck in my signature picture. i was thinking about hitting it hard with the voltmeter tomorrow, seeing where i have power and where i do not, checking my grounds along the way, doing what you said to grounds that arent very strong. i was really hopeful that there was something i was missing that should have been obvious to check, or maybe an electronic part that i don't know about that i need to make sure and check. thanks for your imput, as said before, any response is appreciated. i have a lot i need to haul right now, just trying to get it done.

spankrz · August 1, 2013

^^^^^^^^^^^^^^^ +100 ,stop the shot guning of parts(i think you have at this point) ,,,,,,did ya have the FPCM programmed ?or did someone tell you its plug and play ?let me know ,i can look it up for you if ya want,,,

i believe ya looked past the computor controlled truck thing,,,good luck

no, although my dealer reccomended that i install a new one, they failed to mention that the FPCM needs to be programmed. hopefully this is the "duh" response i am looking for. how do you program them?

gmtech4 · August 1, 2013

no, although my dealer reccomended that i install a new one, they failed to mention that the FPCM needs to be programmed. hopefully this is the "duh" response i am looking for. how do you program them?

dealer programs them

gmtech4 · August 1, 2013

i hope ya have schematics because ya have to understand the systems before self diagnosing ,going by the seat of your pants will not work ,,,,i hope the programing works ,,,,,,

good luck ,,,,,,take it there for a programming first !!!

spankrz · August 1, 2013

i may have to ask my dealer why the reccomended i buy a part, handed me the part new in the box, knowing exactly how i was going to use it, failed to mention that they needed to program it otherwise it was a $150 peice of plastic with a few useless circuts... maybe just a long day. any idea how much time they will charge to program it? half hour? hour?

gmtech4 · August 1, 2013

i dont know ,cant be over an hour ,,,,

here is light reading,lol

Circuit/System
Description

Modules connected to the high speed GMLAN serial data circuits monitor for
serial data communications during normal vehicle operation. Operating
information and commands are exchanged among the modules when the ignition
switch is in any position other than OFF. The high speed GMLAN serial data
circuits must be operational for the vehicle to start due to body control module
(BCM) and engine control module (ECM)/powertrain control module (PCM)
communications. The theft deterrent module and ECM/PCM exchange information
using the BCM as the gateway module allowing communication between the high and
low speed serial data busses. The low speed GMLAN serial data circuit must also
be operational for vehicle starting.

Diagnostic Aids

Sometimes, while diagnosing a specific customer concern or after a repair,
you may notice a history U-code present. However, there is no associated
“current” or “active” status. Loss-of-communication U-codes such as these can
set for a variety of reasons. Many times, they are transparent to the vehicle
operator and technician, and/or have no associated symptoms. Eventually, they
will erase themselves automatically after a number of fault-free ignition
cycles. This condition would most likely be attributed to one of these
scenarios:
- A control module on the data communication circuit was disconnected while
  the communication circuit is awake.
- Power to one or more modules was interrupted during diagnosis
- A low battery condition was present, so some control modules stop
  communicating when battery voltage drops below a certain threshold.
- Battery power was restored to the vehicle and control modules on the
  communication circuit did not all re-initialize at the same time.
- If a loss-of-communication U-code appears in history for no apparent reason,
  it is most likely associated with one of the scenarios above. These are all
  temporary conditions and should never be interpreted as an intermittent fault,
  causing you to replace a part.
Do not replace a control module reporting a U-code. The U-code identifies
which control module needs to be diagnosed for a communication issue.
Communication may be available between the BCM and the scan tool with the
high speed GMLAN serial data system inoperative. This condition is due to the
BCM using both the high and low speed GMLAN systems.
An open in the DLC ground circuit terminal 5 will allow the scan tool to
operate but not communicate with the vehicle. When the scan tool attempts to
communicate with the vehicle a message "no CANdi module detected" will be
displayed.
The engine will not start when there is a total malfunction of the high
speed GMLAN serial data bus.
Technicians may find various Local Area Network (LAN) communication
Diagnostic Trouble Codes (DTC) and no low speed GMLAN communications with the
scan tool.
The engine will not start when there is a total malfunction of the high
speed GMLAN serial data bus.
These conditions may be caused by the installation of an aftermarket
navigation radio module (see bulletins). Some customers may comment of one or
more of the following concerns:
- Vehicle will not crank.
- Vehicle cranks but will not start.
- Vehicle stability enhancement system warning lights and messages.
- PRNDL gear indicator position errors.
- Tire Pressure Monitor (TPM) system warning lights.

spankrz · August 1, 2013

good reading. i guess here is possibly the most important question... does my dealer have to program the module through the obd2 port, meaning i would have to cough up the money for a tow, or can i hand them the module? i am guessing it will have to be obd2 but i hope not.