advice please.

One thing to remember is that people with ASCs often get so absorbed in what they are doing that they ignore the full bladder feeling.  It's not intentional, I do it myself and then it's a mad rush to get to the loo in time.  One of the things in that blurb I posted above was about vibrating watches which go off every so often to remind the child.  Alternatively, if you don't find it to difficult to do/too annoying you could do regular toilet check-ins with your son.

Justme said:

I have tried reward charts taking xbox time and other things like this i am clueless.

When you've tried this, how have you approached it?

We, on the spectrum, are often motivited more by positive, reward-based, motivation, than negative, punishment-based, motivation, and it's important that you phrase things in a positive, rather than negative way.

So, for example, saying "If you wee on the floor you won't get..." or even "If you don't wee on the floor you will get..." are both likely to be much less effective than "If you wee in the toilet then you will get..."

Does that makes sense?

To get rid of the smell try sponging with vinegar.  Or spray Dettol to destroy the bacteria.  Or baking soda and water paste. Rub it into the area and apply distilled white vinegar over it. Blot this up with kitchen paper towels, and repeat it no more than two times. Follow that with a good rinsing of water, blotting up the moisture. It will smell like vinegar for a short time, but the urine smell should not come back.  You could also try Febreze Pet Odour eliminator spray.  And there is a specific product for this type of thing: http://www.urineoff.com/

You need to ensure you get it dry all the way through so the salts in the urine that could be left won't reattract moisture and give off the smell again if there are bacteria left.

If the carpet can stand it you could also hire a steam cleaner.

Some of this may help (there may be more on this website):

http://www.autism.org.uk/living-with-autism/understanding-behaviour/toilet-training.aspx

Habit training

Some children are toilet trained through habit. Habit training is effective for children who may: lack awareness, not understand the significance or meaning related to physical sensations, be limited by decreased or absent physical sensations or have unsuccessfully tried toilet training before. Habit training involves training the body to go at set times. Take your child to the toilet at set times throughout the day, every day. As before, keep a chart to discover the best time to take your child. While sitting on the toilet it is very important your child feels relaxed enough to open their bladder/bowels. Having the tap running in the background can help enable your child to wee and blowing bubbles or blowing up a balloon can help your child to open their bowel. Sometimes having a toy to handle - not one which causes excitement - can be useful to both keep your child on the toilet and relax them. Keep certain toys/books for just when they are sitting on the toilet.

If your child lacks awareness or sensation, they may have to be taught a strategy before getting off the toilet to avoid accidentally weeing on the floor. You can start teaching this process by slowly counting to ten out loud when they have finished weeing before allowing them to get up or giving them a sand timer to look at before they get up. To help your child to independently manage their own toileting routine when they are older, you can buy watches which you can set to vibrate at certain times throughout the day (see resource section). You can then teach your child when the watch vibrates they are to go to the toilet.

Further resources

ERIC (Education and Resources for Improving Childhood Continence) sells a range of bedding protection, swimwear, absorbent pants and vibrating watches.
Web shop telephone number: 01173 012 101
Email: sales@webshop.org.uk
Website: www.ericshop.org.uk
ERIC has a helpline providing advice and information to children, parents and health professionals on all aspects of toileting. Call 0845 370 8008 (Monday-Friday, 10am-4pm) or visit:www.enuresis.org.uk

Fledglings is a charity which helps parents and carers of a child with special needs of any kind to find simple, affordable solutions to practical problems. 
Tel: 0845 458 1124
Email: enquiries@fledglings.org.uk
Website: www.fledglings.org.uk

PROMOCON (Promoting Continence and Product Awareness) has links to various organisations who sell toilet-related products including swimwear, absorbent pants and toilet seats for older children.
Website: www.promocon.co.uk/products.shtml

Tinkle Toonz has musical sensors in potties and ones which can be used in underwear, nappies and pull-ups, designed to alert the child or the parent that the child has 'gone' in his potty or pants. 
Website: www.tinkletoonz.com/special_needs.html

References/further reading

TEACCH (Treatment and Education of Autistic and related Communication handicapped Children)www.teacch.com/toilet.html

ERIC (Education and Resources for Improving Childhood Continence) (2002). We can do it! Helping children who have learning disabilities with bowel and bladder management: a guide for parents

Wheeler, Mary (1999). Toilet training for individuals with autism and related disorders. Future Horizons, Inc.