First start up no pcm flash
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Joined: Aug 2013
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First start up no pcm flash I'm about to get my 5.3 swap finished up. The motor has set for two years with the oil drained. The guy I got it from had a video of it running before it was pulled from the wrecked vehicle but before I spend money on a tune and performance parts can I start it without a pcm reflash just to make sure the engine is good?
On The Tree
Joined: Feb 2012
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From: Glendale, Arizona
Well first put oil in it. Then don't power up the PCM Until you crank it long enough to get oil pressure again. Then power up the PCM I might run for only a sec because of the VATS system. But you can see if it will fire at aleast. My son Just finished his C10 build motor sat for over 2 years fired right up no problems. LSX '85 C10 https://ls1tech.com/forums/conversio...l#post17697393
Thread Starter
Registered User
Joined: Aug 2013
Posts: 18
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Well first put oil in it. Then don't power up the PCM Until you crank it long enough to get oil pressure again. Then power up the PCM I might run for only a sec because of the VATS system. But you can see if it will fire at aleast. My son Just finished his C10 build motor sat for over 2 years fired right up no problems. LSX '85 C10 https://ls1tech.com/forums/conversio...l#post17697393
First I just didnt know if the pcm would work with the modified harness without a flash. Btw the truck pcms have vats? I thought that was only on the early f bodys
On The Tree
Joined: Feb 2012
Posts: 120
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From: Glendale, Arizona
It depends on what you took out of the harness such as down stream O2's and such still might be looking for a signal. I would think it would still fire just run rough. I thought that all GM cars and trucks had VATS. I remember having my sons pcm flashed he said he disabled the vats.
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All emissions are removed except front o2 sensors. And reading the forums on this site say the trucks don't have vats but they have something called pass lock that reads the key cylinder which is similar so I guess it will do the same thing start for a few seconds and die until I have it disabled
On The Tree
Joined: Apr 2011
Posts: 129
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From: Vancouver, WA
I started my LS1 before having the PCM reflashed. I modified my harness and removed all the emissions wiring rear O2's. It would only run for a second and the VATS would shut it down. But it did start.
Sent my PCM in and had it reflashed plugged it in and it instantly fired up and ran.
Sent my PCM in and had it reflashed plugged it in and it instantly fired up and ran.
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All emissions are removed except front o2 sensors. And reading the forums on this site say the trucks don't have vats but they have something called pass lock that reads the key cylinder which is similar so I guess it will do the same thing start for a few seconds and die until I have it disabled
There are lots of people who can flash the PCM and remove all the unnecessary stuff (emissions, rear O2's, VATS, speed limiter, etc.). Where are you located? You may have someone local.
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