So, now I have a new car to deal with, with a new problem. One night car works fine, next morning it'* only got 1st gear, and reverse. No slipping, fluid level is correct, no hard driving the night before. My original thought was that it was in limp mode, and it was in 2nd gear, but it seems to reach higher rpms at too low of a speed and starts out quick with no laziness like a 2nd gear start would have. So I originally think it'* STUCK in 1st gear, but I drove it a little more today and it will shift out of 1st if you're rolling down a hill with no throttle. Then if you give it some throttle, it just revs up, until the car slows down to roughly 30 or so, and 1st gear will grab again. There'* no slipping, no anything. I scanned codes, and since the list is long and full of 'B' codes, and that many of them are connection related, I would think it needs a new BCM anyway. Here is the list...P1571, U1040, U1016, B0041, B1000, B2618, B2655, B3106, B3127, B3128, B3132, B3133, B3137, B3138

Any ideas? A shop I have no faith in told them it'* a bad transmission, but it just doesn't seem right to me.

How many miles on the 01 Impala? My goodness with that many codes it may be electrical.
I would want to remove the battery cables & then inspect/remove connectors to transmission & ensure everything is clean & dry with wires in good shape.
Any chance you drove thru some water?

I agree, you need to get the chassis codes fixed before blaming the transmission. If the ECM thinks it has a traction problem it can cause shift issues.

I don't think that p1571 will prevent the vehicle from shifting......sounds like this guy bought a lot of problems...

I agree.......disconnect battery....check for corrosion.....check chassis ground.....make sure charging system is working.....clear all codes and see which return.......

When in first or reverse, the A and B solenoids are commanded on.....with a scan tool on a road test, the A has to be turned off to achieve second.......

Long overdue update...Finally got back over to look at the car. Checked cables, charged battery, checked body grounds I could find, cleared codes and took it for a drive with the scanner on. According to the scanner, it has 1st and second, and will also shift into 3rd and 4th. 1st seems to work fine, 1/2 and 2/3 solenoids (if I remember right) are on, then one of them shuts off for the shift to 2nd. I don't notice a real shift into second, but the scanner says it shifted. Then over about 30 or 35, it shifts into 3rd, which is not there. If I go fast enough in 2nd,and let off and coast, it'll shift to 3rd, and then 4th (on the scanner), and 4th is also not there. As for codes, I can't get the U1016 to clear, but it'* only listed as history. And when I was messing with the scanner'* other modes, I did get a U1040 to pop up a as a current code. I am assuming the answer is an internal failure in the transmission. Any thoughts on the U1040 code?

To really road test with a scan tool, you watch the A and B shift solenoids.....you also watch the input and output speed sensors......

In first gear, the output speed is approx 1/3 that of the input....in second gear, the output is approx 2/3 of the input......in third gear, they should approx be equal...in fourth gear or overdrive, the output should be faster than the input....the speed out of the output sensor is an indicator of the transmission changing gear in relation to the A and B solenoids changing state....

For example, when second gear is "commanded", and you see shift A sol turn off, while shift B sol stays on(they are both on in first gear), this is second gear and the ratio of output speed to input speed should change from 1/3 to 2/3, indicating that 2nd gear is achieved.....

Makes sense. I have a Mac Mentor Pro. I'm not very educated on how to use it, which is probably obvious. When I was road testing, the datastream had a readout for Shift Solenoid A, Shift Solenoid B, and then it had a readout telling me which gear it was in, along with one giving the gear ratio. Of course, I didn't pay much attention to the gear ratio between 1 and 2, but I did notice it changed from 2 to 3, but I can't remember any of the ratios. I didn't have it setup so I could see either speed sensor when I was watching the shift solenoids/transmission gear datastream. I can certainly run over there again and do another road test. The speedo was functioning properly, and I assumed that ran off the output speed sensor, so didn't think to look any further.