The wiper arm on the passenger side stopped wiping. Someone told me that a small screw on the end of it probably needs tightening but I can't find it. Can you help me ?

The wiper arms are 'pressed' onto the wiper motor spindles, often at times when only one of them stops operating, it is because the splines on the wiper that is no longer operating has become stripped out. and may need to either be replaced or tightened. I would recommend tightening it first, then replacing it if that does not correct it.
You can access the hold down bolt (if it is not exposed) by taking a small screw driver and prying up the bolt cap. The bolt is usually a 13mm, and is more easily tightened by a ratchet and socket of the same size.

loose wiper-spindal conection, make sure wipers are parked and tighten up nut under cover at base of wiper arm

on the end of the wiper arms both sides are two nuts one on each arm ,reset the blades to where they should be on the park position then tighten these nuts and providing you have the right size blabes on then this should cure it

On lower side of wiper arm (closest to windshield) is a nut that has probably come loose. They do this when someone has forced frozen wiper. Tighten nut. It's under a flip up cap

At the lower end of your wiper arm there is a little black cap that looks like a top hat.You can take a flat head screw driver and pop it off revealing the nut.Place your wiper arm at about the same level as the other wiper and tighten.If you have the older style there is a little lever at the bottom that just pushes in.Well hope this helps and goodluck.

Adjustment....There is either a cap on the wiper assembly arm or a small allen nut.

with a cap,take a small screwdriver and pop off the cap, there is a locknut there,loosin it,raise the blade up higher,tightin nut.

Allen screw,loosen raise blade and tighten.

Look at the base of the wiper arm, there is a cover that you can move. There will be a nut behind the cover, this secures the wiper arm to the linkage, its probably loose. Turn the wipers off so they are in the parked position, put the wiper arm in its proper position, then tighten the nut.

In view of the answer from jchaffcom I feel that if there is a Hex on the end of the Wiper Arm the Hex Nut needs Tightened. I have a 2004 Silverado and this is what happened to it. Simply tightening the Nut solved my problem. Try it and get back to me with the results whether good or bad.

Fastest Robe

Most windshield wiper arms usually fail due to a loose nut or rusted and worn out parts. Fixing this depends on how the wiper arm attaches to the vehicle. Fixing wiper arm failure is usually as easy as tightening a nut or replacing a worn out or rusted part.

Here is a step by step guide on fixing this issue.

Step1 Mark the existing wiper position on the windshield using a crayon. This will help you align the wiper arm correctly when you install a new one. Alternatively you can use the Trucks own markings. At the bottom center of the windshield you will see writing and three small dots. The wiper should rest on top of these dots. Step2 Follow the wiper arm down to where it connects with the Truck. You should find a hinged cap at the end. Step3 Lift this cap to reveal the nut and screw underneath. Step4 Use a wrench (or socket and ratchet) to loosen the nut. Step5 Remove the nut completely, leaving the screw stud exposed and the wiper arm free to be removed. Step6 Lift the arm straight up. Wiggle the arm and pull upwards at the same time until the arm slides free of the screw. If it seems stuck, push the arm back down and proceed to Step 7. Step7 Use a battery cable puller to pry the arm loose. Arrange so the large puller screw cap sits on top of the wiper arm screw. The outside arms have flat fingers that should be fitted underneath the wiper arm. Step8 Grasp the handle at the top of the puller and turn clockwise. The puller screw will push down on the wiper arm screw and simultaneously pull up on the wiper arm. A few slow turns should pop the wiper arm free.

if you open the hood look towards the base of the windshield, you should see the linkages for the wiper arms. make sure the linkages are all in-tact and nothing fell off. if the linkages are all good, see if you can move the passenger side wiper with your hand, if it moves freely or with little resistance check the nut/bolt that hols it on at the end of the wiper arm. see if the nut/bolt is loose. tighten if needed. also you can remove the nut/bolt and check the splines on the wiper arm where it presses onto the stud and see if they are wiped out.