91 Z28, LB9 T5
730 ecm

I have been dealing with a code 24 and subsequent idle problems. Speedometer works fine. Replaced VSS, code 24 persists.

Speedo signal comes from the ECM which in turn comes from the VSS right? If so, does this sound like something internally wrong with the VSS circuit in the ECM?

Thanks for the help

 

I agree that it is an ECM issue. The '7730 ECM buffers the raw magnetic VSS signal. It sends that buffered signal out to the cruise and speedometer. There is an additional gate before the ECM uses that same signal.

If the ECM isn't seeing the VSS MPH, in this case I'd say ECM.

Note that if an optical VSS is in use this all changes. But for a '91, stock is magnetic VSS.

RBob.

 

What if he uses a buffer box and the other VSS input on the '730? That is how I used to re-pin original '165 cars.

-- Joe

 

if you are going to use a optical 2k from a 1227165 (A10) vss buffer( pin f of the buffer) you will need to reprogram the eprom for optical vss and use c6 on a 730. The 730 has a internal buffer.

 

True, you have to select "magnetic" or whatever under the ecm switches.

-- Joe