Working on our 02 LB7 that supposedly died while one of the workers was using it. Not clear on whether it died or stopped moving, heard two stories. One of the other guys tried starting it and said it just cranked and did not fire.
I finally got a chance to look at it yesterday and it acted dead so I threw the charger on it, still acted dead. Batteries are new but connections were very bad, cleaned them up and it cranks perfect now but still does not fire.
I noticed the fuel gauge read empty but its been doing that off and on, just to be sure though I filled it up before dragging it in the shop, only fit 9 gallons in it so thats not the issue. Good fuel at the filter as well.
After checking fuses and swapping relay's I decided to check the fuel rail pressure while cranking. This is where my issues came up. I was all excited because of my china Tech 2 so I hooked it up but whenever I try doing anything with the engine it says that it cannot establish communication. Now it is communicating with the truck because I was looking at a lot of other modules earlier and everything was fine, its just the ECM that it does not seem to want to connect to. I have successfully used the special features for the LB7 engine with this Tech 2 on other trucks already so I know it does work. To rule it out though I drug out my EFI Live and laptop and hooked them up, it connects to the vehicle fine but every parameter for the engine that I select it marks as invalid. This really led me to believe it has to be a communication issue with the ECM so I tried connecting to it with the DVT tool and nothing happened there either.
So I am not going to say this communication issue is my only problem, but it seems to be the place I need to start. I do have a U1255 (T-Case), U1016 (ECM), and U1024(TCM) loss of communication codes. I usually never pay any attention to those as they seem to mean very little on any other truck, but it seems I do truely have a communication issue this time. I just went out to try clearing those to see if any came back as I suspected they were from the low voltage issue before but now my EFI Live says it cannot detect a vehicle. I tried unplugging multiple times and still cannot get it to detect a vehicle anymore. So I hooked the Tech 2 up and it will clear the BCM codes but they come back immediately. u1255 is the only one showing up for some reason but I didn't spend too much time going into other modules looking for codes, that was the only DTC that was present and continues to come back in the BCM.
So I am guessing the bad connections could have caused this issue, is it possible the ECM itself is bricked? What else should I be checking? I can't remember if the truck will still crank with a bricked ECM or not, I didn't think so but could be wrong too.
I did find what was probably one of the initial issues that kept it from moving though, the NSBU switch does not appear to be communicating anything. I keep some of those around so I will try one, but maybe its not the switch and part of the gremlins I'm chasing. This truck has had a few lately, it will randomly show no fuel for some reason too. I will be cleaning the grounds to as it does live in corrosion, but looking for some other suggestions on the communication issue right now.
Sorry for the long winded post so early in the morning, thanks in advance though.
I finally got a chance to look at it yesterday and it acted dead so I threw the charger on it, still acted dead. Batteries are new but connections were very bad, cleaned them up and it cranks perfect now but still does not fire.
I noticed the fuel gauge read empty but its been doing that off and on, just to be sure though I filled it up before dragging it in the shop, only fit 9 gallons in it so thats not the issue. Good fuel at the filter as well.
After checking fuses and swapping relay's I decided to check the fuel rail pressure while cranking. This is where my issues came up. I was all excited because of my china Tech 2 so I hooked it up but whenever I try doing anything with the engine it says that it cannot establish communication. Now it is communicating with the truck because I was looking at a lot of other modules earlier and everything was fine, its just the ECM that it does not seem to want to connect to. I have successfully used the special features for the LB7 engine with this Tech 2 on other trucks already so I know it does work. To rule it out though I drug out my EFI Live and laptop and hooked them up, it connects to the vehicle fine but every parameter for the engine that I select it marks as invalid. This really led me to believe it has to be a communication issue with the ECM so I tried connecting to it with the DVT tool and nothing happened there either.
So I am not going to say this communication issue is my only problem, but it seems to be the place I need to start. I do have a U1255 (T-Case), U1016 (ECM), and U1024(TCM) loss of communication codes. I usually never pay any attention to those as they seem to mean very little on any other truck, but it seems I do truely have a communication issue this time. I just went out to try clearing those to see if any came back as I suspected they were from the low voltage issue before but now my EFI Live says it cannot detect a vehicle. I tried unplugging multiple times and still cannot get it to detect a vehicle anymore. So I hooked the Tech 2 up and it will clear the BCM codes but they come back immediately. u1255 is the only one showing up for some reason but I didn't spend too much time going into other modules looking for codes, that was the only DTC that was present and continues to come back in the BCM.
So I am guessing the bad connections could have caused this issue, is it possible the ECM itself is bricked? What else should I be checking? I can't remember if the truck will still crank with a bricked ECM or not, I didn't think so but could be wrong too.
I did find what was probably one of the initial issues that kept it from moving though, the NSBU switch does not appear to be communicating anything. I keep some of those around so I will try one, but maybe its not the switch and part of the gremlins I'm chasing. This truck has had a few lately, it will randomly show no fuel for some reason too. I will be cleaning the grounds to as it does live in corrosion, but looking for some other suggestions on the communication issue right now.
Sorry for the long winded post so early in the morning, thanks in advance though.
