Hello, i have been advised that my steering control module is possibly at fault,when i try to start car, it wont start but sidelights come on and wipers work.no radio.no indicators. can you help please

Your code 21 is just telling you that your left sidelight is out. The shaking and juddering is a different issue and needs a pro grade scan tool computer to see which sensor needs replacing.
21 Failure of left sidelight.

Vauxhall Astra Fault Codes - - Driving Test Tips

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Vauxhall Astra Fault Codes List ; 21, Failure of left sidelight. ; 22, Failure of right sidelight. ; 23, Failure of reversing light. ; 24, Failure of number plate ...

take it back in for a steering module check
the hyundai I 30 elantra has a recall ( 2015) for loss of power steering due to a loss of steering assistance from an electrical power steering fault
There is a control module that applies full assistance at low speeds , parking or cornering but reduces the assistance effort at speeds where assistance is not really required
from your description, it indicates that the control module is not functioning correctly and so you are advised to take it back in for a recall check or a warranty check on the system

cam/crank position sensors
immobilizer issues
ignition control module
injectors nor working
low fuel/ no fuel pressure
run the fault codes to determine which of those need fixing

The Internet, though, has a large number of web sites where you can buy service manuals and schematics from bookstores, publishers, and other collectors. Here is just a sampling of what sites are out there:

Chilton Repair Manuals
http://www.chilton.cengage.com/

Haynes Publishing
Haynes auto manuals
http://www.haynes.com/

Factory Service Auto manuals
http://www.factoryautomanuals.com/

Vintage Books
Vintage books com Rare used and out of print books
http://www.vintage-books.com/

AutoLit
http://www.autolit.com/home.htm

Check manual and look at fuses see if you have listed a Lights control module you may find it is as simple as a fuse, I had a similar problem on my Volvo my video on this may help you although it's for the S80 and not your car but the fault sounds the same ? look at video vortash2 on youtube S60 and S80 dashboard lights problem. hope this helps

Hello. The code: U0212 is for the Steering Column Control Module. You need to change it. Go to a well known junkyard that sells good conditioned or descent condition iteams and look for your style and year like your car. Good Luck.

well it might be you started

You will have to find a Jag specialist who has a facility to read the fault codes on the E.C.U.