cylinder 3 & 4 no spark

[Dustytrix]

OK here goes, I swapped cam into used 5.3 , it was running when I bought it. Ok I got it cranked today but it has no spark on 3 & 4 cylinder. Swapped coils, checked for grds, for volts, for reference wire. All wires checked out good coils worked good on other cylinders. Swapped spark plug wires and plugs. Still have no spark on 3 or 4. What could I check now?

[Dustytrix]

I checked the codes last nite, its showing p0353 and p0354. Control circuit malfunction, I will keep digging today.

[Dustytrix]

I did a compression test today, cyl 1-145 cyl 3- 144 cyl 5-145 & 7-144 I didn't work on even side since I got this reading. That tells me the valves and rings are working. Still throwing code p0353 p0354 I cleared it with hp tuner and it runs good for about 5 secs maybe then starts missing again.

[BR3W CITY]

If it doesn't "move" with the coil, then its occuring before the coil (i.e the plugs or a mechanical factor isn't causing it). Put a meter on the actual harness to the coil and see what you've got. There is a ground on the head too, make sure that one is on.

[Dustytrix]

I checked all wires at harness plug , all are working as supposed to. Is there any thing else that could cause the ecm to throw this code

[BR3W CITY]

3 and 4 are the 2nd cylinder from the front on each side. So its weird that the same one on either side failed at the same time. Are those the only 2 codes? I'm not familiar with a false-positive for those particular codes.

[homemade87]

po353 , po354

Short to voltage or ground on driver circuit , Open on driver circuit , Loose connection at coil or broken connector locks , Bad Coil , Faulty Powertrain Control Module

My guess is being you have 2 cylinders doing the same all of a sudden , some how you have damaged the connectors . You really need to inspect those connectors . Not just see if there connected . Be sure the the pins have not pushed out or bent or even take them apart for inspection .

[Hart_Rod]

Swap coils 1/2 to 3/4, see if the problem follows

[Dustytrix]

Swapped coils already problem stays at 3&4 . Today I ran a new wire from ecm to connector on # 4 coil it didnt help. I am about ready to say its ecm but don't want to waste 2 credits . I am using a fluke digital meter and it is reading volts steady on the coil pulse wire, I don't know if it is a steady voltage or if the fluke is so sensitive that it doesn't show the pulse.

[87chevy.com]

As far as wire testing, have you ohm tested the harness?
Clint

[Dustytrix]

Yes Clint ohm test has been done I found another ecm that I might try just to see if it fires on those coils before I try to swap tunes

[Dustytrix]

Finally got the no spark issue fixed, installed 02 ecm and it cranked right up. No misfires. The other ecm must have bad coil drivers. Not to go back and straighten out all my ecm wires.