Just swapped in a rebuilt 1992 3VZ. I'm getting an intermittent code 42, which is "SPD signal is not input to the ECU blah blah". Does anyone know if the FSM is referring to the Vehicle Speed Sensor (VSS) located on the transmission housing? Or is it the speed sensor located behind (on) the instrument panel cluster? The speedometer is rock steady, not bouncing. Does the ECU alter engine performance with a code 42 (like it does with the code 52, knock sensor) or is it just reporting a failing sensor?

 

Into what?

On older trucks, the speed sensor is inside the combination meter (instrument panel) and is driven by the speedometer cable. On newer trucks, there is no speedometer cable, the speedometer is electronic, and it is driven by VSS1 on the back of the transfer case. I don't know if there is a year for the change, or if it has something to do with configuration. If you KNOW you have the older system, here's the manual page with the diagnostics: http://web.archive.org/web/201102052.../6combinat.pdf

VSS2 (the sensor on the side of the transmission), measures the speed of the transmission. Which may or may not be proportional to speed, depending on the transfer case. So code 42 refers to the signal from VSS1, wherever it is located.

I don't know the exact use of that signal by the ECM, but I'm not aware of any code that is "just for your information." So, yes, I would not be surprised if code 42 results in drivability issues.