P0405 Chevrolet -

Question

I have a newly acquired minivan with an LX9 3.5L V6 engine. and 4T65 transmission.

I get tcc chuggle/fishbite at cruise 60 mph or so. Acts like trans trouble and makes the tcc jump in and out. Thankfully, tests show the following:

I disconnect egr connector as a diagnosis, and then things smooth out except for the egr codes. Chuggle fishbite gone; that clears the trans as root cause.

It appears that the excess leanness from too much EGR is perhaps the root cause of an engine smoothness issue.

Answer 1

P0403 Exhaust gas recirculation circuit malfunction
P0405 Exhaust gas recirculation sensor A circuit low
At 60 mph the EGR is open and this will  not cause a leaness , Unless  when  it is partial open at idle. then there is a rough idle condition,