Changing PCM best way to transfer existing tune.

[forrer13]

Hi Guys,

I have picked up a used 0411 PCM from an 02 Suburban for my LS swapped BMW in attempt to fix my transmission issues. This new 0411 PCM is using O.S. 12216125.

This will be to replace a 4896 PCM using O.S 12212156. The tune I am currently working with started from this PCM and is running the engine great, but will not control the 4L60E transmission properly.
As soon as the engine starts commanded gears jump all over the place from 1 to 4 then 2 or 3, with no logic or reason. Attempt to drive and the car immediately shifts up through the gears way, way, too early.

I have replaced all the trans solenoids and pressure manifold, I have confirmed good electrical connections from the PCM connector to the solenoids and pressure manifold switch.
I have no PRNDL on this car but I do have a P/N switch on the shifter grounding blue pin 34 when in P or N.

I am now suspecting I have a bad PCM that is somehow grounding the trans solenoids when it is NOT being commanded to by the tune. It seems fine with key on, engine off, but as soon as the engine starts the commanded gear does crazy things.

What is the best way to transfer my current tune to the new PCM?
Can I just do a Write Entire?
This should cost 2 credits right?

To be sure my tune is not causing the transmission problems, would it be best to use the stock tune in the new Suburban PCM and manually edit the engine tables and various values to match my current tune? Leaving the transmission controls stock for now. Reason I would want to do this is in case the transmission part of my current tune is corrupt somehow, if that's even possible.
This should also cost 2 credits, correct?

Thanks guys, this problem has really got me stumped......

[5FDP]

License the new computer and open that file along with your old tune in the compare feature. Use the comparison log and only copy over the engine side information.

Do NOT write entire your old tune into that computer. Just copy the data you want.

[forrer13]

Thank you very much for that. I have started doing exactly that but ran out of time last night. Its very convenient that after I copy one set of data over from one tune to the other, then I can compare the differences and make sure they are all zeros.

[forrer13]

I think I might be onto something.
Turns out the VSS in the SPEDO tab was set for a manual car, 17 pulses per rev instead of a 4L60e at 40 pulses per rev.
I haven't confirmed it yet but it sure makes sense that this would cause the transmission to shift prematurely, as the PCM thinks I am going 2-1/2 times faster than I actually am.

[forrer13]

I think I might be onto something.
Turns out the VSS in the SPEDO tab was set for a manual car, 17 pulses per rev instead of a 4L60e at 40 pulses per rev.
I haven't confirmed it yet but it sure makes sense that this would cause the transmission to shift prematurely, as the PCM thinks I am going 2-1/2 times faster than I actually am.

Well the VSS pulses per revolution was indeed the problem. I made the change from 17 to 40, wrote the new tune and everything is perfect!
I can put the shifter in D4, gently let off the brake and the speedometer in HP Tuners gradually climbs to about 12 MPH, shifts to second and climbs to about 15 MPH and sits there happily at idle. A gentle push on the gas pedal and at 20 MPH shifts to third. This matches the commanded shift speeds perfectly. Hit the brakes, back to first and zero MPH as expected. FYI the car is still in the air on the Quick Jacks.

I am 100% sure it is correct now as the behavior when I let off the brake in D4 is completely different and predictable.

Thank you all for you help.