Been tinkering on this car for the last few months finally got it back on the road again yesterday with a used ECM n new prom chip along with fuel pump relay. Never had this code before it has an aftermarket speedo that's never worked. Code seems to only set at mid to lower cruising speeds. Trying to figure out where the sensor is located sounded like behind the speedo or on the back of the transmission?

 

The stock speedometer had the Vss in the gauge. I would look at the cable end in the transmission tail housing.
700r4 still? Tcc locking up ? If the Vss is missing Probably the best fix is a 2k ppm retrofitted sensor from tpiparts.net. you would ground one wire and hook the other wire to pin a10 at the ecm.

 

Gotcha yeah looked around last night behind speedo all I could see was a little black plastic piece with like 3 wires to it. Yeah still 700r4 I believe n everything locks up n runs fine until the ses light comes on then tranny n idle along with shift points go all whack. Will look into that conversion part today. Weird speedo cable is still there n it spins just never been an issue until now.

 

The stock one behind the cluster was green and incorporated onto the circuit panel.
https://www.tpiparts.net/inc/sdetail/7586
do you have a scanner or aldl to usb cable to see the Vss signal?

 

The stock one was actually a little yellow box mounted to the back of the cluster. It was optical; used a LED & photocell to literally "look" into the speedo and watch the little magnet that the cable spins, as it whirled around. 2000 pulses per mile therefore. Its wires should be pink/blk (ign), blk/wht (gnd), & either tan or brown, can't recall for sure (signal).

I've never seen one like what Tuned linked. Doesn't look factory to me.

 

Oh yeah gotcha makes sense yeah probably long gone. Sweet just seen that on TPI parts n no I don't just use the paperclip method to pull codes. Buddy has one across town. Just stumps me it was never an issue n outta the blue acts up.

 

Sofa Hince the name retrofit lol.
the Vss could be green or yellow on the cluster.
was the old chip a custom tune?

 

Gotcha yeah it was well sorta just a generic one it was a hypertech chip for a '86 305 TPI the other chip I have now is the same except it's for '87-'89 350 TPI. Got it new cheap off someone I know.