Start off by inspecting the quality of the print before it gets to the fuser and try a new set of toner. There's no specific order this has to be done in, but it's often easier to start with the toner.
The first thing to do is to replace the toner. A good 3rd party toner will work for this step if you don't feel like spending a lot in case the printer is bad and you don't want to be tied to this series if toner doesn't help. In a lot of cases, the toner runs out before the chip reports 0% or the toner supply outlasts the actual cartridge. In some cases, it happens because the toner is old and beginning to degrade. This happened on my M401n when I had to replace the toner due to drum issues with ~50 pages left. If the toner is genuine HP, it should have a date like this on it:
If your problem isn't caused by the toner, it's going to be a transfer roller, ITB (Intermediate Transfer Belt) or fuser. HP integrates the other components into the toner carts on a lot of printers. Do a "halfway test" and see if it's strong before it gets fused to the page. If this is the case, it's a cut and dry fuser problem. The problem with this test on color models it can be difficult due to the layout of the ITB. However, some of them will be worse then others. The idea behind the "halfway test" is it is used to give the user an idea of what the problem is and where it happens,
If the print is weak before it gets fused, it can be one of these:
If the print is strong until it gets fused to the page, it has a fuser problem and is absorbing toner.
If the fuser has an issue, the replacement cost and difficulty varies. Your printer is one of the more notoriously bad ones, since you need to take apart a good chunk of the printer to access the fuser. I would suggest looking for a new printer if it turns out to be the fuser on this model. The ITB is even more difficult to replace then the fuser on this series.