I have an intermittent issue that come and goes with ignition cycle. When reading live data ($85, A138) if the "DRAC is Current Sensor" = No/Magnetic, then my PCM reads the vehicle speed and the TOSS as about 1/2 causing it to

1)Shift at very high RPM and
2)Think the TISS/TOSS ratio is >4 and maxes out line pressure causing hard shifts.

On the rare occasion that DRAC is Current Sensor = Yes, TISS/TOSS and ratio read correct, pcm vehicle speed seems correct (a little lower than speedo like 40 vs 45).

The speedo always looks good.

Looking at o-scope signals
The AC signals from TISS, TOSS, and VSS look good and freq/amplitude tracks with speed.
The DRAC to PCM signal look like a clean sq wave at 5v that freqency tracs with speed.

So how does the PCM decide to use the drac or not, and when it decides no and uses magnetic, why does it seem to half all of the values of the TOSS and vehicle speed?

Appreciate any insight anyone might have, or any other troubleshooting steps I might be able to take.

Thanks,

Tony