I have a 2003 Buick lesabre custom and went out this morning car started right up put it in drive and NOTHING reverse 1st & 2d gears work fine but no drive engagement. Checked fluid level and it'* fine, fluid looks like it'* suppose to reddish, any suggestions?

Ok, you have manual 1....you have manual 2.....do you have manual 3?

Have you checked for transmission codes?

Only engages in reverse,1st & 2d.. no trouble codes

Surprised there are no trouble codes......I assume when you manually shift, from 2nd to third, it just stays in 2nd, it doesn't go to neutral, and if you then manually shift from 3rd to 4th, it just stays in 2nd, it doesn't go into neutral......

If the PCM is seeing a request for third gear, and is not seeing the correct ratio of input to output, so it should set a code....

In first gear both A and B solenoids are on for first gear.....since you have first gear, the solenoids are ok......if one or the other was bad, it would be like starting out in 2nd or 4th gear......

Looking at a shift chart, it'* looking like you might have a problem with the 3-4 clutch not applying......

A scan tool will tell you if the A and B solenoids are being commanded on and off, correctly.....looking at the input output ratios will tell you if the vehicle, is responding to the solenoids....

1st , both A and B on, output 1/3 input(rpms)....

2nd, A off, B on, output 2/3

3rd, A off, B off output 1/1

4th, A is on, B is off, overdrive, the output is greater than input....

So if the scan tool shows a request for each gear manually, and the solenoids turn on/off at the correct times, it looks like the 3-4 clutch, or it'* apply circuit.....

I'm not a tranny guy, this is my best guess....