2001 Caddy STS Trans or Electrical Problem? ...HELP!

[only1vip]

I was driving on the HWY and pressed on the gas to kick the car into overdrive, when I did that, the gears shifted up and down 4-5 times jerking the car. The speedometer also droppped and rised from zero to 30, then 0 to 70, etc...

I carried on driving without pushing the car, it drove fine. I parked the car for an hour once I reached the destination. I drove the car again and it was doing the same thing, but this time at around 30-40 mph, shifting erractically batween 1-3 gear. After about a minute, the car would not even leave first gear. I parked the car. The next morning, the car drove fine again.

This has happened three times since then. If I leave the car parked overnight, or for about 8 hours or so the problem disappears. If I park the car somewhere for an hour or so and drive again, the problem comes back.

Does this sound like a trans problem, or more like an electrical module problem?

Any help is much appreciated.

[GOT2B GM]

Sounds like a VSS gone bad or a short in the VSS wiring.

[only1vip]

Thanks for the feedback! Any Idea how much the fix will cost me and if it a fairly simple fix that i can do myself?

Any other Ideas?

[GOT2B GM]

Depends on the accessibility of the sensor. I've only had my 01 STS for a couple weeks myself.

[Ranger]

The VSS is the easy one. It's on top of the right output shaft housing. Jack up the right side and pull the wheel and you should be able to see it through the wheel well.

[only1vip]

Thanks Ranger!

[submariner409]

Vss........

[only1vip]

Thanks for all the help guys... I've replaced the VSS and my caddy is running beautifully once again!

[submariner409]

Thanks for the feedback.........It'd good to know that some cadillac things are (relatively) simple fixes.

Did you learn any special tricks for someone else with the same problem ????

[only1vip]

I may have spoken too soon... Last weekend I took the Caddy on a road trip after the fix (800 miles highway and city driving) and had absolutely no problems at all. Just last night, I went out and the SAME PROBLEM came back, while driving home from the grocery store.

Is there a test that I can perform to check if the sensor is good? Should I try replacing the sensor with another one (since they are fairly inexpensive)? Could this be a grounding issue? If so, where should I be checking for the improper grounding?

Odd thing is, the problem is popping up when I park the car for around an hour. When I stop the car for gas, no problems...when I park for a few hours, no problem... I can't make any sense of it.

As always, any and all help is much appreciated!

[00 Deville]

Originally Posted by only1vip

Could this be a grounding issue? If so, where should I be checking for the improper grounding?

The VSS sensor only has 2 wires going to it both wires come from the PCM.

VSS goes to PCM
pin A --------- Pin 57 of connector C1
pin B --------- Pin 56 of connector C1

I would start by cleaning both the VSS and PCM connectors with alcohol or electrical contact cleaner. If that doesn't work I would try another sensor. Did use use an AC Delco sensor?

[only1vip]

Thanks for the reply Deville 00... Unfortunately I was in a rush and the dealership was closed, so I did not use an AC Delco sensor ... I purchased the sensor from Advance Auto... Should I buy the AC Delco part and put that in?

[00 Deville]

I would definitely try the AC Delco sensor this time.

[only1vip]

I'll try that out and let you know how that went...

What would I do without this forum?

[submariner409]

While you're in there, use a few shots of Brakleen or Radio Shack Electronics Cleaner to blow out the connector pins/socket. Something as simple as a poor connection plays hob with the tiny voltage pulses generated by these sensors.