2008 Denali XL possible ECM Failure?

[Rich Reno]

I am chasing what I thought started as a fuel issue, but looks more and more like a ECM problem. We have had quite a few struggles with the truck and that is why we got BBP tuning in the first place. Currently the truck wont start, and is showing a P0230 code

It seems like the ECM isn't commanding the fuel pump to stay running. The pump will run for 2 seconds, then shut down when the key is turned to on, which from my understanding is correct. Then when you crank, it won't turn over at all, unless you bump the key several times to "prime" the line, then it will run for a few seconds, up to a minute depending on how much you prime it. I have inspected all of the wiring that I can see for the FPCM, and nothing has corrosion, or is worn through. I have also replaced the FPCM, fuel pump, and pressure sensor at this point, trying to eliminate something that would be having the system not keep the pump running.

My fuel pressure through the autocal reads 765kpa, or about 110psi... which i know it isn't from checking the test port on the fuel rail, but it reads the same even with a new pressure sensor installed. At this point, I am leaning towards the ECM, as it is what is supposed to be reading and interpreting all of this data, and also telling everything else to work.

Is an ECM failure that common? I know I have reprogrammed a replacement TCM on another vehicle, but I am not sure if the same approach would work for the ECM or not.

THoughts?

 

[thompsoj22]

did you have to program/initialize the fpcm, or was it plug and play?

 

[Doubeleive]

the fpcm has to be programmed

 

[Doubeleive]

I am chasing what I thought started as a fuel issue, but looks more and more like a ECM problem. We have had quite a few struggles with the truck and that is why we got BBP tuning in the first place. Currently the truck wont start, and is showing a P0230 code

It seems like the ECM isn't commanding the fuel pump to stay running. The pump will run for 2 seconds, then shut down when the key is turned to on, which from my understanding is correct. Then when you crank, it won't turn over at all, unless you bump the key several times to "prime" the line, then it will run for a few seconds, up to a minute depending on how much you prime it. I have inspected all of the wiring that I can see for the FPCM, and nothing has corrosion, or is worn through. I have also replaced the FPCM, fuel pump, and pressure sensor at this point, trying to eliminate something that would be having the system not keep the pump running.

My fuel pressure through the autocal reads 765kpa, or about 110psi... which i know it isn't from checking the test port on the fuel rail, but it reads the same even with a new pressure sensor installed. At this point, I am leaning towards the ECM, as it is what is supposed to be reading and interpreting all of this data, and also telling everything else to work.

Is an ECM failure that common? I know I have reprogrammed a replacement TCM on another vehicle, but I am not sure if the same approach would work for the ECM or not.

THoughts?

fuel pressure should not be that high, should around 65 pre-start and minimum 45 psi running, I would test with a gauge on the fuel rail and do a leakdown test also

 

[Rich Reno]

did you have to program/initialize the fpcm, or was it plug and play?

I did the Dorman unit that was plug and play, no programming.

The fuel pressure isn't that high actually, it's about 50 if I bump it a few times. It holds the pressure for 5 minutes as well. But as soon as it is running the pressure just drops until it dies

 

[thompsoj22]

the fpcm has to be programmed

If im not mistaken the fpcm controls pressure via pump speed, Our vehicles have no return circuit to bleed pressure back to the tank, this may explain the "extremely high" fuel pressure? But the ECM should recognize the fpcm as fubar and throw a code?

just saw your reply so it isnt the module.

 

[Rich Reno]

If im not mistaken the fpcm controls pressure via pump speed, Our vehicles have no return circuit to bleed pressure back to the tank, this may explain the "extremely high" fuel pressure? But the ECM should recognize the fpcm as fubar and throw a code?

just saw your reply so it isnt the module.

You are correct, that's why it only runs the pump for 2 seconds with the key on until you are cranking or the engine is running

 

[thompsoj22]

I did the Dorman unit that was plug and play, no programming.

The fuel pressure isn't that high actually, it's about 50 if I bump it a few times. It holds the pressure for 5 minutes as well. But as soon as it is running the pressure just drops until it dies

your positive the fuel pump replacement is solid in regard to connections fuel/electrical, at least it fires so you are close. Do you have access to trouble shooting such as alldatadiy, there will be a sequence for the most likely component. All those new parts that vehicle wants to start doing what you expect it to do, start and drive you anywhere you want to go. hang in there, so the initial problem hast changed at all?

 

[Rich Reno]

There was some additional codes initially, the fpcm did have signs that water was in it. Before that it wasn't even powering up the pump.

 

[Doubeleive]

if you bought that dorman local I would consider exchanging it for another one just to rule it out, dorman is usually ok stuff but not always.

 

[thompsoj22]

it is a long shot but CPS gone bad? i know this sensor normally is good or bad, but it is critical to ecm rpm recognition. see if you can simply give the harness/connector a push/pull and see what happens, this is simply what id do, it sounds like you have skills, these vehicle electronics/emission controls can adjust/control the engine for effeciency 100 times per second but cant tell you what is wrong when they fail? F'ing engineers

 

[Rich Reno]

if you bought that dorman local I would consider exchanging it for another one just to rule it out, dorman is usually ok stuff but not always.

I did buy it local, but they only had one...

 

[thompsoj22]

There was some additional codes initially, the fpcm did have signs that water was in it. Before that it wasn't even powering up the pump.

was this connection coroded? its going to be somthing simple, this component changed the problem, check this harness?

 

[Mechanic421]

So do you have any way to read data on a scanner? Really need a scantool.

 

[Rich Reno]

So do you have any way to read data on a scanner? Really need a scantool.

I have an autocal, but that is what is making me think that it's the ecm, the data I'm pulling doesn't look normal across the board.

I wouldn't write off the cps, but I replaced that about 2 years ago... So I doubt it

None of the harnesses or connectors had any corrosion on them, and nothing looked scorched or miss aligned

 

[Mechanic421]

Can you post a screen shoot?

 

[Mechanic421]

I have an autocal, but that is what is making me think that it's the ecm, the data I'm pulling doesn't look normal across the board.

I wouldn't write off the cps, but I replaced that about 2 years ago... So I doubt it

None of the harnesses or connectors had any corrosion on them, and nothing looked scorched or miss aligned

Is there fuel pump duty cycle or maybe command data ?

 

[Rich Reno]

Is there fuel pump duty cycle or maybe command data ?

In efi live dvt commands there is a fuel pump duty cycle, but the dvt isn't giving any normal responses.

I'll try and mess with it again and see if I can post some screen shots

 

[Mechanic421]

So you have tried to command manually in tests/functions test and no response? Sometimes in efilive you have to have it on in two different places. I am not really all that great at computer shit but I get by. Hopefully someone smarter will chime in. But if you can command fuel pump check output at computer and go from there. Anti theft? May need to scan whole truck.

 

[Doubeleive]

just curious, how is your voltage? how old is the battery? when it runs for a minute what kind of voltage are you getting? i'm wondering when you are getting funky readings on the autocal could be voltage related. just something to consider.