hey everybody. i have a 2004 bonneville gxp. just today it started shifting hard. after driving it for a while, the ses light came on. i checked it and it read dtc'* p0502 twice and at one point it read p0503. after i replaced the vss, it still does it. the p0503 code only came on that one time, but the p0502 still does. anyone had a problem with this? i've heard it could be the ring the sensor uses, the wiring, or the pcm. any way to test these individually or anything like that?

theP0502 coming up twice in one read just means that the code is a repeater meaning it trips twice although it only really tripped once.

I'll shoot a PM to SGP358 and make sure he sees this thread. He is our resident Trans expert.

Thanks for posting!

Both of those codes are related to your VSS. You stated you replaced the VSS and the problem is still there. So it stands to reason the sensor is not the problem. Check the plug for damage. You should also check for any damage to the wires, so you will need to test those. If all this tests OK that leaves the reluctor wheel and that'* inside the diff cover on the diff. The VSS is a magnet. Did you find any metal on the sensor?

i didn't see any metal. it looked fine. i visually inspected the wires and didn't see anything. what do i test the wires for?

Track the wire to the other end and test for continuity on that wire from one and to the other. That will tell you if the wire is broke.

ok. thanks. how often is the reluctor ring or the pcm the problem?

I've not heard of a reluctor wheel go out, it'* just a ring with teeth on it. If moves past the magnet and the magnet picks that up. I've not heard of any 2004 PCMs go bad, older PCM like 1995/1994, but not the newer ones. SGP358 is your best bet for answers in this area.

Most times that I see a VSS problem on one of these cars, it usually is the connector or wires. I have seen the wires chafe and break about 2-6" from the VSS. You can buy a pigtail from a Delco distributor or a GM Dealer.

Did you lose the speedo?

If the diff happened to be self destructing, you should have had metal on the VSS because it'* a magnet. I could see metal beating it up and causing an issue, but if there was none...

cool. thanks. i'll start looking for one today. i don't know if i did because it stopped working about a year and a half ago.