driveability

The CTS V forum are slow and since these cars are very similar ........
2016 CTS V 45K miles no known addons, been doing this for 10K miles and 8 months or so. Otherwise run, drives fantastic.
Intermittently, however every day. Symptoms are mainly the 8-speed auto transmission locks up in one gear. From startup cold drive away to after 10 minutes shifting from 6,7,8, gear down to a lower gear maybe 3rd gear not sure. Won't shift up or down in any mode.
Need to cycle the key 1 - 4 times with a short 1/2 mile to 3-mile cruse around to get it to clear, mostly the rest of the day.

Secondary things that happen are numerous, but don't all happen each time.

1 Advanced front lighting flashes an alert in the right side of the IP.

2 stabilitrak, rear axle alert, power steering, traction light flashes on and off.

3 Park assist off, back up camera inoperable,

4 tachometer at idle flickering to a lower rpm. (The engine does very slightly studder)

5 oil temp from normal to 0 psi fast than it could actually happen.

6 coolant temp at the IP gauge falls from normal to low again to fast of a reaction to be accurate.

7 HUD changes from one setting to (speed limit to the radio station) another setting.

8 Briefly my scan tool reads no data. After a key cycle everything pops back up.

Have not had it looked at as yet
25 years of dealership Tune-up and Drivability under my belt but 20 years ago.

driveability

Any thoughts on this just might help out, now I have removed the TCM and am taking a good look at the connector and terminals.

blackbyrd

iTrader: (14)

this sounds like water in a connector or a bad ground somewhere.

how/where do you park it? If rodents have access to the car, it start looking for evidence they have been in the engine bay or anywhere you can see wiring harness. the bad news mid 2000's soybean oil was as a substitute for the oils in plastics like hoses and wire coatings... which makes it very tasty apparently. Had a chipmunk actually chew threw the evap system on my silverado once upon a time so I had a gross leak code. Found they had chewed the hose and the barb on the tank.

likewise for water intrusion around connectors particularly if it happens when dew or rain are prevalent. Back in my technician days, had a customer with a nissan sentra who claimed on key on it would go haywire and not start. He had it towed in one day cause we could never duplicate the issue. Sure enough the cluster was flickering all its lights and relays were clicking. In his case the relay box under the hood wasnt sealed so any moisture from rain or dew would setting in the bottom of the relay box shorting everything out

driveability

(blackbyrd) Thanks for your input
update,
so, i pulled the TCM harness straight up next to the radiator so I could study the connector and the male and female terminals. I used a welder tip cleaning tool to rough up the female terminal, Also I connected and disconnected the PCM 3 connectors, hit everything with electrical terminal spray and left the TCM under hood next to the radiator. Been driving it for 3 weeks 800 miles or so with no issues. The car would act up daily and or be in remission one to three days at the longest for the last 6 months. Looked back and I'm at a full 30 days free of any issues. I have left the TCM and the connector isolated and untouched for the 30 days. I am going to handle the TCM / connector and related wiring. Tug on the harness and connectors handle the TCM a bit. Hopefully the car will act up again and the action / reason is repeatable as to isolate the cause further. Below is a pic of my 987 Cayman / LS3 / 6 speed build