VSS code and no reverse?

[cadman20]

1997 grand prix GTP

My daughters car has issues going into reverse, you have to rev it up to about 3000 to 4000 rpm and then it pops into reverse, the car also is throwing a P0502 code for the vehicle speed sensor. Does the sensor have anything to do with the reverse issue? Tranny shifts fine in all forward gears.

I had the tranny rebuilt 6 months ago, it is still under warranty, but if the VSS is the issue, I will replace it myself.

Thanks in advance.

[BNaylor]

If your speedometer is reading properly and the forwards gears work then I don't think the VSS issue is related to the reverse issue. If the tranny is still under warranty best to take it back to the shop.

In order for the P0502 (Low Input) DTC the PCM must see a low vehicle speed relative to a large engine speed in a drive gear range. Output speed is <150 rpms.

[cadman20]

Just went to Autozone and picked up a sensor ($50.00) Oreillys didn't have it in stock ($23.00)....typical.....

Any way, just replaced the sensor and car now has reverse... Don't know why or how, just glad it is fixed.

Thanks

[BNaylor]

Weird problem. Glad you got it fixed and thanks for the feedback.

Interesting symptoms after the DTC sets. The PCM will command maximum line pressure which explains having to rev up and slamming into gear, diasables shift adapts and then since the VSS signal is bad uses the ISS as a reference signal in a fail safe mode.

One for our record books.