LQ4 swap lost communication, spark, and fuel.

[C450]

Hey guys, I don't post much but I am on here quite a bit. I have done a LQ4 swap into a 74 GMC. Tuned with EFI Live. I was trying to read the gauges with my laptop but was not able to connect. I tried my scan tool with the same issue. No communication. I started it 6 more times since then and now I have also lost spark. Now my fuel pump only comes on for a split second when I turn on the key. I've bypassed my pump wiring to make sure the pump still works. The pump turned out fine. I have checked my grounds and added extra ground wires just to be extra sure it is not a ground problem. Double checked my battery positive terminals to the data link connector and PCM. Everything checks out fine. But still no communication to a scan tool and no spark. Could I have a bad PCM? If so, what would have caused it? If I am to switch PCM's, is there a PCM with an operating system I should be looking for? Anyone else have any ideas? I appreciate any help.

[joecar]

How is your ALDC/OBD2 port wired...?

When you key on, does fuel pump relay activate for 2 seconds...?

[C450]

Positive and ground are currently wired to junction blocks wired directly to the battery. I may have fixed the current issue. I replaced the PCM with one from a S-10. Fuel pump was coming on for only half a second but as soon as I hooked up the new pcm, the pump comes on for a couple of second like it should. It also fixed the no spark issue. I'm doing a full flash right now to get back to my silverado operating system. Truck was also running rough before. Would fall on its face off of idle. I'm hoping this also takes care of that issue.

[C450]

I had this problem with the last pcm as well. I tried doing a full flash and when it was almost done this popped up. Anybody know what causes this?

[C450]

I'm just trying to change operating systems. From a 12212156 to a 12205612. Am I not doing this correctly? I tried a full flash. Should I be trying this a different way?

[C450]

I didn't try this earlier but after work I will try flashing a totally stock tune to see if this failure happens again. What happens if I keep having this problem during a full flash? Will it screw up this pcm?

[C450]

Well I answered my last question. I bought a used PCM from a S-10 yesterday. Tried a full flash and came up with the checksum error. Now this PCM is having the same problem as the first one. No communication with a scan tool, no spark, and the fuel pump only kicks on for a split second. So are these PCM's junk or can I save them? I obviously can't keep buying computers just to license and screw them up with EFI Live. What am I doing wrong?

[C450]

Joecar, my connector is wired like so.

Serial Data Pin 2 to Blue Connector Pin 58.
Pin 4 and 5 are wired to a junction block wired to battery ground.
Pin 16 is wired to a junction block wired to the positive battery terminal.

[joecar]

Can you bench program any PCM...?

[C450]

I'm not currently set up for bench programming. I'm trying to flash them while in the truck. Should I build a separate bench harness?