Perfect for a VSS signal to OBD1
I purchased this for my 1989 C3500. Before I purchased the truck the transmission had been replaced with an older version that did not have the reluctor for the speed sensor. I've been running it for years with no speed sensor but using an aftermarket electric speedo and hall effect sender. This worked fine for telling how fast I was going but it did not send a signal to the ECM. These OBD1 units don't require the speed for much, but they do use it for deceleration and idle trim. The truck has always had issues with a high idle in park after driving for a while. The speedo and wiring are a 3 year only on these trucks and kind of difficult to set up. The signal goes to the speedo then buffered and sent to the ECM. Calibration for gearing and tire size is done using resistors in certain orders. Using this I tried to install the factory speedo and also switched the resistors around for my particular setup. These are soldered in the circuit board. When all was said and done, I did not have a functioning speedo. I admit that could be completely my fault. Either in my attempt to rearrange resistors or some other issue. I reinstalled the aftermarket speedo and used this unit to send a signal to the ECM only. In that variation it worked perfectly. The ECM no longer says it has no VSS signal and my idle in park issues are gone. For me this was the primary reason I bought the unit and it fulfilled that 100%. It comes with a manual that is easy to understand and has diagrams for just about any combination of sender to speedo or tach that you can come up with. In my case, I got the most important feature I needed and may try using it again later with an unmodified speedo.
Verified purchase: YesCondition: New