Car moves gears but won't drive

Hi have a Cadillac CTS 2004 I was on my way to take my son to school I stopped at the stop sign & my car will not accelerate front or back.It turn on fine but won’t move.i put the scanner & it gives me codes po420 & po430. Did the transmission fluid/filter change about 4 months ago.

Both of those codes refer to a problem with the catalytic converter(s), or the oxygen sensor(s), but neither of those situations should result in an inability to engage the transmission.

I don’t think that you have any alternative to having the car towed to an independent transmission shop for diagnosis.

Whatever you do, do NOT take the car to Lee Myles, Cottman, Mr.Transmission, or–God forbid–AAMCO unless you want to be overcharged for substandard workmanship.
Look for an independent trans shop that has been in business for at least three years.
Sincere good luck with getting this problem resolved!


+1 to VDC’s advice.
Write back. We do care.

Could just be a linkage problem is all. I presume you are able to physically move the lever to D & R from N or P, but when you step on the gas it’s the same as in N or P, you don’t move. Is that all correct? If you seem to move a little, that’s more likely some problem with the transmission. But if you don’t move at all, it behaves exactly as if you are in N or P, pretty good chance there’s a simple fix for that one. You’d need a shop to take a look at the linkage is all.

Yes your right the car goes into all gears but doesn’t move when I give it gas.Do you think the scanner will tell me if I have a bad transmission?

A reading of the diagnostic codes should provide a clue at least.

I got Po420 & Po430

I don’t think those are transmission codes. Those are usually codes associated w/problematic catalytic converters. Is the check engine light flashing? If so the cat problem and the symptom you have may be related.

No the check engine light is not flashing just on. So if it is the car needs transmission fluid n I do it again the transmission oil/filter change will the work again?

Your just going to need the transmission looked at. A fluid change won’t solve this.

You need to be familiar with the data screen on a professional scan tool to make an assessment in that way.

Does the indicator in the instrument cluster correctly show each selected gear? Does the accelerator pedal respond to your input?

Possibly. Low transmission fluid can definitely cause the “car won’t move in D” symptom. I had that problem myself on my truck one time. It was in the shop for a complete transmission rebuild within a week. Fixed it up like new straightaway. I’m not saying that’s what you’ll need, there’s some diagnostic work needed before that conclusion can be reached.

A little tutorial on automatic transmissions: There’s two basic things that control their behavior, the vehicle speed, and the intake manifold vacuum. Not too much goes wrong w/the latter usually, but there’s a pump inside the transmission that pumps the transmission fluid to a pressure corresponding to the vehicle speed. Higher speed, higher pressure in other words. It must do that function accurately. If that isn’t working, the transmission won’t work correctly. And if the pump doesn’t have enough fluid to pump, it won’t be able to reach the proper pressure to operate. .

I think that @GeorgeSanJose has the answer.

And a code reader will do nothing. It will not tell you that the shift cable/lever came off the transmission.


…and if this’s the problem with my CTS BUT, no check engine and shutting off the car and restarting it enables the shifting of gears again…but I feel it wanting to fall back into its previous state? I can rev the car in any gear and go nowhere, fluid is new and no leaks. So much of this car is computer reliant, almost too much.

From the codes it looks like you have a clogged CAT. I would recommend removing both 02 sensors and seeing if the vehicle will run

Andrew , the person asked for help over 2 years ago and never posted again .