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.