Painless VSS + 16197427 = no VSS reading.

[Six_Shooter]

I'm using a painless VSS (2 pulse older version of the 60115), I am using a 16197427 PCM to run a Crossfire equipped 305 and 4L60E, in a 1971 Chev pick up.

The only issue I have (other than the fuel pump dieing on me earlier today), is that the ECM does not read a VSS signal.

I have used this VSS with a 1227747, with one wire connected to ground, the other connected to the optical input, it worked fine then. I also had it connected to a 1227730 running S_AUJP for a short while before the owner of that vehicle got the 4ppr VSS, also a painless.

I am using $0D, and have the "VSS not from DRAC" bit selected, since that's what some threads on TGO indicate needs to be done when this PCM is swapped in place of a '7747.

I am using this VSS due to needing the cable drive for the trucks original speedo.

Now the only thing I haven't tried yet, that came to me after coming home and leaving the truck on the hoist until I get a new pump in the morning, is adding a pull up resistor.

Has anyone used this combination before? Any insight?

[EagleMark]

Not real sure but thought the 427 needed a four pulse? But it should still read?

Maybe putting in a DRAC would clean up the signal to work... I have a couple DRAC and VSSB is I think what the 427 used.

[Six_Shooter]

From everything I have read on TGO, this should work.

The optical VSS buffer is said to work going straight into the ECM, and this VSS mimics that signal, at least it's supposed to be.

I have a few DRACs kicking around too, but the OEM reluctor wheel is a 40 tooth wheel, so 40 pulses per revolution, which the DRAC then changes to a pulsed signal, much like the optical signal.

[dave w]

I've done something similar.

I converted an 87 GMC 1 Ton to a '427 PCM and connected the original '7747 VSS signal directly into F13 of the '427 PCM. I did not use a DRAC. I use DataMaster TTS to data log with, and the MPH is correct in the data stream.

From my experience, I am wondering if the optical VSS is a 2 pulse (2K) VSS? The 87 GMC VSS is a 2 pulse VSS. The '427 conversion I did works fine with a facotry 2 pulse VSS.

From my experience, an aftermarket VSS can be tested with an Ohm meter. The two output wires from the VSS should change resistance from less than two ohms to more than 100K ohms 2 times per revolution.

[Six_Shooter]

Yeah, I went back through my pinouts, and noticed that F13 had the 2PPR input from the DRAC, so that would likely be fine for a non-E tranny. The crossover chart that someone made on TGO showed F12 as being the input for the VSS when doing a '7747 to '7427 swap.

The information I have found in the last couple days indicates that tranny functions need the 40PPR input, from the DRAC. So it looks like my grandfather will be making a reluctor wheel and sensor mount.

I just wish I knew this before the swap, I would have done the VSS and speedo thing differently. Oh well.