Here's a problem I've never run into before with any vehicle. A customers 09 sierra with active fuel management has 4 injectors not firing. Cyl's 1, 4, 6, 7. There are also 4 codes in the computer: p3401 p3425 p3441 p3449. These are VLOM solenoid control circuit fault codes. I've read about VLOM solenoids shorting out. I took them out and checked with a DVOM for shorts between power and ground on all the connector pins and all the solenoid terminals as well as shorts to the VLOM body. None were present. I understand how the AFM system works. It closes valves and shuts off fuel injectors on cyls 1, 4, 6 and 7. If there are certain faults related to various sensors, the AFM system won't engage. My problem is that, coincidentally, 4 fuel injectors (on 1, 4, 6 & 7) will not fire. Ever. The engine will barely run. The valves are all moving. I've repaired several 5.3's with bad AFM lifters and most of the time, the lifter collapses and won't actuate the valve or is intermittent. I'm leaning toward a faulty PCM. I have +12v at the injector plugs but never a ground signal on 1, 4, 6 & 7. Noid light won't blink. What do you guys think? Could the AFM section of the PCM be fried? I'm hesitant to buy a used PCM due to VIN not matching and anti theft not matching. I have a good scan tool but it's no Tech II. It's an Autel DS708 with no programming capabilities. Thanks in advance!