You can find code information at the manuals link at the top of this forum. Look at;
Combined Toyota Factory Truck Maintenance Manuals.
Follow the link and you will find download or on line versions of your truck shop manual. You will have to spend some time searching to find your specific codes. The diagnostics will say what the possible causes may be and how to test or troubleshoot the suspect parts. You may find some tests will require the use of some test equipment not in the average owners tool kit.
The mauual should help you find the cause of your problem.
Clifton