Car keeps going into limp mode after short drive. Giving errors DSC not available, Cats system fault, Engine system fault, add park brake fault. Along with messages also get codes P2135, U3005-16, U0405-92, and a U0401. These codes were read with a generic reader and are nonspecific from what I could find. Any ideals where to start. Looked at all wheel sensor seemed to be ok.

Most likely code P2135 is the major fault to be dealt with. PCM bad. Powertrain control module. But your mechanic has to get onboard.
Don't push the car hard!

The FIRST and BEST place to look is a Low Battery. Literally 90% of all electrical gremlins are caused by low battery voltage. Your battery HAS to be at least 12.6 volts after sitting for many hours.
First step to remedy is to CHARGE the battery with a GOOD battery charger, not a maintainer or trickle charger. Most auto parts stores will charge and test a battery for you at no cost.

Electrical glitches’re usually to blame for DTCs. Starting with battery, followed by earth points and alternator.

Are you the original owner? Do you know the service history? Tons of helpful threads here using the search function.

BATTERY!

A selection of unrelated errors is immediately suspicious. What you don't say in your post is as important as what you do say. Is this a daily driver? Do you keep the vehicle on a battery tender?

1. test the battery - it is almost certain to be undercharged or failing.
2. if you need a replacement, charge it overnight BEFORE fitting
3. clear the DTC's
4. complete at least two "drive cycles"
5. if "limp mode" returns, check for codes with a compatible code reader or JLR SDD

Graham

Battery checks out ok, voltage at12.8 after sitting 24 hrs. When car is running the voltage read around 13.7. Looking at TB now trying to find way to test it's operation. Would like to test on the car if I can figure it out. The manual doesn't show much. Will let you know if I find something Still searching for something on the throttle petal sensors also..

Texts about the U0401 and U0405 kept referring to broken wires or faulty connectors/ harnesses to the PCM/ECM.

Ok, finally have some different news on my problems! didn't take off TB but did have some success with it. Never found a way to test or change just TP sensor. After some wiring cks reconnected TB and drove car around 100.. Finally changed SAI switching solenoid, hoping this get rid of P0414 code permanently. Think I still need a new TB, P02105 showed up today, still researching this, throttle actuator control system. , If I ever get all codes cleared then I can tackle changing out the top. Thanks everyone for your help..