2002 Monte Carlo Code 717

I have a 2002 Monte Carlo SS and I'm getting a code 717 "Input/Turbine Speed Sensor Circuit No Signal". At first it was no big deal, the light would come on and go off with no drivability problems. I took it to a the shop to get their opinion and of course they told me that the transmission would have to come out and be torn down for a mere $600-$2500 for a diagnosis, that it could be one of two things: A) A sensor inside the transmission had failed, OR B) The exciter ring that triggers the sensor was in the process of sheering off and was causing the codes. I doubted this because the light would go off and stay off for a few days. A sensor that is not getting a signal will not allow the light to switch on and off, it usually will stay on all the time. It it possible that the sensor itself is failing, but not the exciter ring. Then it began to shift rough when the light was on. Only from 3rd to 4th upon acceleration and vise-versa upon decelartion. Within a day or two it began to shift into neutral on the freeway or at cruising speeds of 45+ and the speedometer would fluctuate all over the place, then the speedometer would regain the correct speed and the car would be fine. It only does this if the car has warmed up to operating temperature. Makes sense to me that it's the speedometer sensor that is failing and not an internal sensor (the vehicle speed sensor is accessable from the outside of the transmission, a $48 fix). Any ideas?

You can try replacing the vehicle speed sensor (VSS) but it may not fix your problem. The input speed sensor (ISS) is not the same as the vehicle speed sensor (VSS) that runs the speedometer. ISS is located inside the tranxsaxle housing facing the drive sprocket on the input shaft. For P0717 to set the PCM is detecting no signal. If the VSS sensor was the cause the VSS DTC codes would set first before ISS. In order to generate P0717 there can be no VSS error codes detected as a condition.

The reference voltage for the ISS comes from the PCM. Without pulling the tranny some troubleshooting can be performed before deciding it's an internal problem and big bucks.

You can disconnect the PCM 80 pin connector, make sure its clean and tight. Next disconnect the 20 way connector on the driver's side, top of the tranny. Disconnect and reseat it. If that doesn't help, on the 20 way connector with a mulitimeter in ohms position, the ISS sensor can be checked for a range of resistance.

At 20 way electrical connector pin S to V (tranny side):

68 degrees F = 893 - 1127 ohms
190 degrees F = 1132 - 1428 ohms

If not in this range the ISS is bad. Good luck!