Is there any certified GM techs in the group? U0109 is driving me insane.

[Jmix91]

2009 Tahoe 5.3L

DLC - P0506 & U0109

Repairs and actions so far.

- replaced FPCM 3x
- PROGRAMMED 4x (last 2 times at Chevy dealership)
- replaced fuel pump
- replaced throttle body
- replaced EVAP purge valve
- replaced EVAP vent canister
- replaced FPCM Connector
- cleaned both bell housing grounds (driver side)

There’s no blown fuses nor corrosion on fuse box. The truck will start and run, after 30 - 45mins it will stall. Will not turn over after. However letting it sit for a while it will crank and run. There is a rough idle and constant drop in the rpm’s (580-610).

FPCM data reading is attached.

I’m a mechanic myself but of course I do not know everything. I’m assuming it may be a can bus issue since FPCM is the only DLC showing. the master tech at my job refuse to work on my truck even when I offered payment directly to him. I’m extremely frustrated as I do live in my vehicle due to an unfortunate situation (ex fiancé mother death) and is stuck out of state. I just wanna get this truck back up and running so I can go wash clothes and have better chance at survival. And go get a second job. Please help.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally assist you with your issue, but other members of this Forum much more knowledgeable than me in this area will chime in.

PS: Folks do not need to be certified GM techs to help you out, but we do have some GM certified folks in this Forum.

 

[Fless]

There’s no blown fuses nor corrosion on fuse box. The truck will start and run, after 30 - 45mins it will stall. Will not turn over after. However letting it sit for a while it will crank and run. There is a rough idle and constant drop in the rpm’s (580-610).

The "won't turn over" (which means to me, no crank) would appear to be another issue. The fact that it starts when it does turn over needs to be diagnosed apart from the FPCM.

 

[Doubeleive]

I know you replaced it already but..
Recall ID # 85456 - FUEL SYSTEM, GASOLINE Plus Hide Details
Recall Date:
MAY 06, 2009
Model Affected:
2009 Chevrolet Colorado
Summary:
GM IS RECALLING 27,188 MY 2009 CADILLAC ESCALADE, ESCALADE HYBRID, ESCALADE ESV, AND ESCALADE EXT; CHEVROLET AVALANCHE, SUBURBAN, TAHOE, TAHOE HYBRID, AND COLORADO; AND GMC YUKON, YUKON HYBRID, YUKON XL, AND CANYON VEHICLES. THE FUEL SYSTEM CONTROL MODULES MAY HAVE A CONDITION IN WHICH AN ADHESIVE SEPARATION OF THE ROOM TEMPERATURE VULCANIZING (RTV) SEAL BETWEEN THE SEAL AND THE HOUSING MAY ALLOW WATER TO SEEP INTO THE MODULE.
Consequences:
WATER IN THE MODULE COULD CAUSE A SHORT OR OPEN CIRCUIT, ILLUMINATION OF THE SERVICE ENGINE SOON LAMP, SETTING OF DIAGNOSTIC TROUBLE CODES OR THE ENGINE MAY BE HARD TO START, MAY NOT START OR MAY STALL INCREASING THE RISK OF A CRASH.

also, my guess is it is loosing communication somewhere and heat/cold effects it, I would inspect the harness all over and try wiggling wires to see if it triggers the problem
U0109 Lost Communication with the Fuel Pump Control Module.

The Fuel Pump Control Module communication is via the High Speed GMLAN Serial Data Circuit. There are three modules on the circuit plus the Data Link Connector under the dash.
1. If you have anything connected to the DLC, such as a Scangauge, disconnect it.
2. Disconnect the battery.
3. Remove the connector for the Transmission Control Module and inspect the pins.
4. Remove connector X3 to the ECM Module. It is the connector on the left (inboard
connector) and inspect the pins.

GM has experienced problems with "fretting" corrosion on connector pins in many of their vehicles and have a Service Bulletin regarding it. The corrosion appears as a gray film on the pins. The problems show up more on the low voltage Serial Data circuits. The High Speed GMLAN circuits have Tan & Tan/White colors.

This is, admittedly, a long shot, but it is easy to do as the Transmissions Control Module and Engine Control Module are next to each other in an easily accessible area.

GM recommends a light coating of this on connector pins:

 

[opfor2]

"GM recommends a light coating of this on connector pins" Light coating of what?

 

[Doubeleive]

"GM recommends a light coating of this on connector pins" Light coating of what?

no idea.... just something that came up under that lan code
these kinds of things can be really hard to find, sometimes it take's a oscillscope with a exerienced tech
which means "dealer"

 

[Geotrash]

"GM recommends a light coating of this on connector pins" Light coating of what?

Most likely dielectric grease.

 

[Jmix91]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally assist you with your issue, but other members of this Forum much more knowledgeable than me in this area will chime in.

PS: Folks do not need to be certified GM techs to help you out, but we do have some GM certified folks in this Forum.

 

[Jmix91]

no idea.... just something that came up under that lan code
these kinds of things can be really hard to find, sometimes it take's a oscillscope with a exerienced tech
which means "dealer"

Yeah imma have to just bite the bullet and take it to the dealer

 

[Doubeleive]

Yeah imma have to just bite the bullet and take it to the dealer

I would explain the problem to the "service manager" be sure to get him aside and explain the issue in detail, then he will know the best guy to put on it.
usually the service manager is the most knowledgable than the rest of the counter monkeys and also knows which tech to put on it.

 

[Jmix91]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally assist you with your issue, but other members of this Forum much more knowledgeable than me in this area will chime in.

PS: Folks do not need to be certified GM techs to help you out, but we do have some GM certified folks in this Forum.

Seems like GM techs do not know neither. They said the fuel pump is causing the FPCM to overheat and shut off causing the loss communication. However I just warranty the fuel pump and boom same problem

 

[j91z28d1]

have you confirmed that when it dies that the fuel pressure goes down too and the scanner matches what's on a mechanical gauge?
we have this little Ford industrial 2.5L at work that has the returnleas style fuel system and sometimes the fuel pressure sensors get funky and cause all kinds of weird running since the ecm is using the pwm signal to chase the fuel pressure from a incorrect sensor. we either gotta put a gauge inline, or at this point we just keep extra sensors in stock and swap them as a check


just a random thought

 

[BG1988]

2009 Tahoe 5.3L

DLC - P0506 & U0109

Repairs and actions so far.

- replaced FPCM 3x
- PROGRAMMED 4x (last 2 times at Chevy dealership)
- replaced fuel pump
- replaced throttle body
- replaced EVAP purge valve
- replaced EVAP vent canister
- replaced FPCM Connector
- cleaned both bell housing grounds (driver side)

There’s no blown fuses nor corrosion on fuse box. The truck will start and run, after 30 - 45mins it will stall. Will not turn over after. However letting it sit for a while it will crank and run. There is a rough idle and constant drop in the rpm’s (580-610).

FPCM data reading is attached.

I’m a mechanic myself but of course I do not know everything. I’m assuming it may be a can bus issue since FPCM is the only DLC showing. the master tech at my job refuse to work on my truck even when I offered payment directly to him. I’m extremely frustrated as I do live in my vehicle due to an unfortunate situation (ex fiancé mother death) and is stuck out of state. I just wanna get this truck back up and running so I can go wash clothes and have better chance at survival. And go get a second job. Please help.

i hope this fixes the issue for you

https://static.nhtsa.gov/odi/tsbs/2012/SB-10043829-6448.pdf

 

[BG1988]

Most likely dielectric grease.

Genuine GM dielectric grease. P/N 12377900

 

[swathdiver]

2009 Tahoe 5.3L

DLC - P0506 & U0109

Repairs and actions so far.

- replaced FPCM 3x
- PROGRAMMED 4x (last 2 times at Chevy dealership)
- replaced fuel pump
- replaced throttle body
- replaced EVAP purge valve
- replaced EVAP vent canister
- replaced FPCM Connector
- cleaned both bell housing grounds (driver side)

I do not show U0109 as being for a GMT900 in my shop manual for either my 2009 or 2013 trucks.

So let's solve P0506. The shop manual says that the engine is being dragged down and you say she's stalling. So what's causing her to stall? A pulley? Alternator? Power Steering Pump? Torque Converter? Restricted Exhaust?

I'd pull the belt and spin those items first.

Sorry about your luck, been there before. Put the Good Lord first and everything will work out alright.

 

[Jmix91]

have you confirmed that when it dies that the fuel pressure goes down too and the scanner matches what's on a mechanical gauge?
we have this little Ford industrial 2.5L at work that has the returnleas style fuel system and sometimes the fuel pressure sensors get funky and cause all kinds of weird running since the ecm is using the pwm signal to chase the fuel pressure from a incorrect sensor. we either gotta put a gauge inline, or at this point we just keep extra sensors in stock and swap them as a check


just a random thought

I just replaced the fuel pressure sensor yesterday and same results

 

[Doubeleive]

2009 Tahoe 5.3L

DLC - P0506 & U0109

Repairs and actions so far.

- replaced FPCM 3x
- PROGRAMMED 4x (last 2 times at Chevy dealership)
- replaced fuel pump
- replaced throttle body
- replaced EVAP purge valve
- replaced EVAP vent canister
- replaced FPCM Connector
- cleaned both bell housing grounds (driver side)

There’s no blown fuses nor corrosion on fuse box. The truck will start and run, after 30 - 45mins it will stall. Will not turn over after. However letting it sit for a while it will crank and run. There is a rough idle and constant drop in the rpm’s (580-610).

FPCM data reading is attached.

I’m a mechanic myself but of course I do not know everything. I’m assuming it may be a can bus issue since FPCM is the only DLC showing. the master tech at my job refuse to work on my truck even when I offered payment directly to him. I’m extremely frustrated as I do live in my vehicle due to an unfortunate situation (ex fiancé mother death) and is stuck out of state. I just wanna get this truck back up and running so I can go wash clothes and have better chance at survival. And go get a second job. Please help.

View attachment 412816

have you pulled the fuse box up and looked to see if there is any corrosion?

 

[j91z28d1]

I do not show U0109 as being for a GMT900 in my shop manual for either my 2009 or 2013 trucks.

So let's solve P0506. The shop manual says that the engine is being dragged down and you say she's stalling. So what's causing her to stall? A pulley? Alternator? Power Steering Pump? Torque Converter? Restricted Exhaust?

I'd pull the belt and spin those items first.

Sorry about your luck, been there before. Put the Good Lord first and everything will work out alright.

that's an interesting code I've never heard of. hmm trying to think what could drag an engine down like that. I've seen ac compressors locked up and the belt slip and burn up but didn't die. I once had a Cavalier given to me as a kid because it kept dying out, it was the torque converter lock up not unlocking when coming to a stop at red lights. it would restart in park, but die out as soon as it was put back in gear. till it was towed home and cooled off. probably not simple unplug these days like it was back then.


I'm very curious what you find.

 

[j91z28d1]

I just replaced the fuel pressure sensor yesterday and same results

does it have the rear air ride auto level pump? seems like I remember a youtube video on a can bus that traced back to the module back there. saying it's prone to corrosion because of the location. ended up using a jumper wire to loop the can and bypass the module to the system that had failed years before and wasn't worth fixed.

my memory is horrible these days, but seemed like it was a random no start as well.

 

[Doubeleive]

that's an interesting code I've never heard of. hmm trying to think what could drag an engine down like that. I've seen ac compressors locked up and the belt slip and burn up but didn't die. I once had a Cavalier given to me as a kid because it kept dying out, it was the torque converter lock up not unlocking when coming to a stop at red lights. it would restart in park, but die out as soon as it was put back in gear. till it was towed home and cooled off. probably not simple unplug these days like it was back then.


I'm very curious what you find.

the heat soak issue makes me think it is a poor electrical connection, I would start at the fuse box now that other things have already been done
like something is expanding when hot loosing connection and then contracts after it sits and cools making contact again
same kind of thing can happen when it is cold out and then works when it warms up.