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In the middle of my 6.0 t56 swap in my 2005 RCSB Silverado truck that was originally a V6 5 speed. I'm using a 2003 2500HD DBW harness for the swap and the V6 PCM that came with the truck tuned for DBW V8 and manual transmission. VATS turned off.
When I go to start the truck the it will only crank for about a half second. Cycle the key and it will only crank for about a half second again. I confirmed it's not the starter by putting a test light on the started solenoid wire and I've swapped relays at the fuse block to rule that out.
Doing some poking around on the start relay at the fuse block I found that the Starter Enable Control Wire (Yel/Blk at Pin D12 in C2 Block) from the PCM is commanding the start relay but only for about a second then shutting off. I can hook a ground to this wire and it functions as it should.
I'm guessing the PCM is finding a fault in the start relay system then shutting it off? Maybe something to do with the auto crank? Missing something in the tune? Tune is attached.
I had this same problem with my swap. Also using the v6 pcm. You need to go into the system options and turn off the low crank res. Go to system-general-system options - then where it says crank low res and gmt 800 - you will have a 1 - change that to a 0 - rewrite and it should crank as long as you hold the key. hope this helps.
07-01-2018, 04:04 PM
4.3 5 Speed to 6.0 6 Speed Start Problems
