I did some trial and error tonight with a few PCM's and think I figured out how to tell if a PCM will support Drive by cable. (it has to have chip to run the idle air control motor)

I had previously thought if the Serv. No from an express or GTO match another pcm from a truck, it would work, however this is not the case. I was trying to get cable throttle to work on my car, but it would not control the idle. I was using express van calibration, etc. Even tried GTO calibration, still nothing. Engine starts and idles around 1500. In HP Tuners it would not let me control idle, and you could not hear IAC move when you key off.

I got another pcm, this one actually from a GTO, and it worked great.

2003 PCM Cable Throttle DOES WORK:
Serv. No. 12576106
Hwd. No. 12570558

2004
GTO PCM, Cable Throttle DOES WORK:
Serv. No. 12586243
Hwd. No. 12583659

2004
Silverado PCM, will not work with cable throttle:
Serv. No. 12586242
Hwd. No. 12593660

2005
Express PCM, Cable Throttle DOES WORK
Serv. No. 12589462
Hwd. No. 12589161
Almost every other 2005 or 2006 PCM I have seen from a Silverado, has Hwd. No. 12589162. This Hwd. No. WILL NOT work.

I did come across a 2007 Express 6.0 that had DBW. To make things confusing, its Serv. No was 12602801, but Hwd. No. was 12589161, SAME as an 05 Express PCM. Go figure...I dont know what GM is doing.


now for some pictures, to physically see what is different INSIDE the PCM. See the red circled areas. It looks like one driver chip and a capacitor is all that is different. I have not looked at the surface mount stuff to see if any different. You can tell if your PCM has this chip without having to fully remove the circuit board. Just look for the ends of the pins sticking up at B67U1. If there are pins, its there..if no pins, its not.

The first three pics are the GTO PCM that had the chip and extra capacitor.