08 ram 1500 4.7L speed sensor

Good reason. There is no speed sensor. Vehicle speed is computed by a Hall Effect sensor mounted in the rear differential. That , in turn, feeds the ABS, and the chassis computer where the pulse train is measured against time and then divided by a series of divisors for the various outputs like the speedometer and display computer overhead. Normally, the GPS itself measures speed (VMG) by calculating position change over time. Steve

Ye of little faith...

Your input was of great value. Thank You...

No wonder. Thanks.

Okay... now that all the histrionics are over with, let's see if we can actually offer some assistance.

The Pioneer unit simply wants a pulsed input from the rear wheel speed sensor. While not absolutely required (as it can determine speed via GPS), it does help the system respond more quickly to changes in vehicle speed. Given that it's designed to go in to a multitude of vehicles, it will automatically calibrate itself to determine the pulse-per-minute to vehicle speed ratio (again, using the GPS readings).

So, in short, all you need to do is tap the rear wheel speed sensor wire before it goes into the ABS controller. Unfortunately, the 2008 wiring diagrams aren't yet available on Dodge's site

so you're going to have to wing it with the wiring. Examine the connector at the rear differential, identify the colors of the wires, and find them up at the ABS computer connector. Assuming they didn't change anything from '06 to '08, you're looking for pin #42, a 20-gauge dark green/white wire. That's the positive side of the speed sensor, and probably what the Pioneer is looking for.

Tom, I have never questioned you before, but this time I must question whether this will work. If you tap into the sensor lead there, is it before or after the pulse amplifier? If it is before, the signal level is very weak and cannot drive anything but the input to the pulse amp. Perhaps I have misunderstood your directions and you are refereing to the output of the amp. Steve

Well, let me ask you this: if you hooked up a multi-meter to the sensor, and set it to read A/C millivolts, do you think the meter would register anything as the wheels turned? And if so, why do you think the electronics in the nav unit would be any different?