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5.3 to 6.0 swap won't stay running help please!!!


camaroandyz28
05-18-2009, 07:30 PM
ok well its been a while since i've been on so long that i forgot my username and password. well i have an 03 silverado which had a 5.3. while on an off road adventure i hydro locked my motor and blew a rod. I then decided to buy an 03 6.0 out of a 2500 hd. over the past two weeks i have finally got the motor back in and ready to go except for a couple stupid things. today i put the starter in and tried to give it a turn. on the second try it fired up. now the exhaust isn't completly tight and i have to get two o2 sensors becasue the 6.0 has different pre cat sensors.black trianguler connectors apposed to the white square 4 pin. i used the computer from the 6.0,but tranny from the 5.3. when i start it it will run for a second and die. now i'm not getting a securty light which is what i first thought it was and i dont think its running enough to set a code since my scanner is saying there's none. i know it has fuel pressure at least when i turn the key because it starts. now i know this is a shot in the dark but any idea why it wouldn't stay running???? also the second i try to give it gas it dies even quicker. it will probably run for 2 or 3 seconds and stalls?? need to get this thing back on the road and any ideas on when to start would be much appreciated.. thank you

kahjdh
05-18-2009, 09:45 PM
I would try the passlock procedure, leaving key on for ten minutes and then cycling it that way 3times, and see if the security light goes out.

ukrkoz
05-18-2009, 10:26 PM
not that i know what i'm talking about, but my guess is, because you have mismatched powertrain components, it throws BCM out of whack, that throws ECM out of whack, and it disables fuel supply. hence security code. i doubt any "procedures" will work, unless you have matching componentry for EVERYTHING.

would have been easier to overhaul engine, don't even need to pull it out of engine bay.

J-Ri
05-19-2009, 03:08 PM
not that i know what i'm talking about, but my guess is, because you have mismatched powertrain components, it throws BCM out of whack, that throws ECM out of whack, and it disables fuel supply. hence security code. i doubt any "procedures" will work, unless you have matching componentry for EVERYTHING.

would have been easier to overhaul engine, don't even need to pull it out of engine bay.

I was thinking that too. I'm fairly certain that a PCM on an '03 can't ever be replaced with a used one. I think the VIN number has to match in all the modules or it won't work. Some people claim it's anti-theft, some claim GM just wanted to sell more new modules. I'd lean toward the second one :) You can't use a used on because the module has to be flashed to the vehicle before it can be used, and that is stored in ROM. Just plain old read-only, can't be undone as far as I know. If you screw up the flash procedure, you have to get a new module; so I think it's safe to assume that you can't undo an old one. Having a transmission in there that the 6.0 wasn't supposed to have could also cause problems, but that's just a general "could be", not positive there, but it can't help any. I think you're headed to a dealer for some modules and some programming on this one... Or reinstalling the 5.3...

EDIT: I got to thinking about it some more, why not put the original PCM back in there and see what happens? LTFT should compensate plenty for a possible difference in injector flow rate (if there is any), and I think everything else should be the same, but I'm not 100% sure on that. If the connector is the same, the inputs and outputs just about have to be the same. Wont hurt to try anyway, if it would run bad shut it off to avoid any possible damage, but I think the worst that would happen is it would not start.

ukrkoz
05-19-2009, 05:53 PM
indeed, you have TCM governing trannie, then BCM governing anti theft features, and then ECM, governing both and the whole entire powertrain and other electric features that can be controlled electronically. OF COURSE, GM wants it all to match and cooperate. they might be lousy car makers, but how to rip extra buck they know well.
so no, i really doubt what you've done is workable. for the sake of what was broken, all you had to do was to remove engine heads, drop oil pan, and you can replace any part in the pistons assembly from the bottom. sounds scary, but is, actually, very doable.

wafrederick
05-19-2009, 07:53 PM
Rebuilding that engine,the 5.3 is not worth it these days.Consider the price of the machine work that needs done and it might need a crankshaft which is probally junk.A reman engine is cheaper than rebuilding these day and there is one advantage: a better warranty.Jasper is one choice with a 3 year 100,000 mile warranty.The 6.0 was not made up to the the 4l60E and uses the 4L80E instead which is a stronger transmission

j cAT
05-20-2009, 08:06 PM
swap only the motor...leave the pcm o2 sensors etc alone....

it does sound like the secuity/bcm...conflict..

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