Youtube has a million basic multimeter tutorials to familiarize you with that part. So I'll let you figure that out.
1002 implicates the RSX_VDDC, which is the core voltage for the GPU. Set your multimeter to resistance, continuity or diode mode and read the resistance across the +/GND rail on the NEC/TOKINs. If it reads the same resistance as when the probes are touching each other, then you have a short. But you would have a 3001 if that were the case, so you don't have a short. Normal resistance there should be 2- 3 Ohms or so. If it's less than 1, that's bad. It can indicate worn, oxidized or deformed solder joints that are nearing a fault (like a BGA/Bump defect), or it can indicate damage to the die circuitry from elcetromigration.
Here are some nominal resistance measurements from important voltage lines to the RSX. This and more can be found on
Victor's private file pile.
View attachment 35320
If any of these are significantly different (say off by 10%) then there could be an issue with that voltage line. Check the scematics (also in Victor's treasure hoard) and track down the source of that voltage line and measure each resistor, capacitor and SMD for shorts. If they seem normal, it's probably an issue on/under the RSX itself. After removal the RSX can be "ohm tested" (each voltage drectly) to measure nominal resistance and verify it's okay before attempting to reball. That method is not !00% however, we'de really need a chip tester with pogo pins to measure every pad to know for sure. But this method is pretty good. But if you are going to that length, you may as well replace with a NOS 40nm RSX and mod chip.
EDIT: And here are the main RSX voltages and test points.
Now, most of that is a waste of your time. I'm pretty sure with those errors you need to replace the tokins. Start with one CPU and RSX tokin each. Remove them (carefully) and replace with
3 of these for each tokin replaced (24 per console if replacing all 8. Plan to do that anyway). Clean the Flux off thoroughly and then measure resistance again. If there is a short, you need to fix it before testing. That's basically all the multimeter is good for here - verifying you installed the TaPol caps correctly. Test the console after replacing one tokin on each side and see if your errors change. If not, replace one more tokin each. I'm betting the 3003/3004 disappears and you'll be left with a 1002.
If after the first or second tokin the errors change, the you know you're on the right track. Replace all of them and don't forget the bridge wires. Before, the tokins were acting as the bridge. If you don't provide a bridge wire after replacing all the tokins, the tantalum will explode (not kidding)! You don't have to worry about bridge wires if using my Tantalizer PCB, that's the main point. If you don't want to use it, I recommend a palisades arrangement like this...
View attachment 35321
...but using the larger caps I linked before. It might be harder to fit them on, but you can make it work easy enough.
Lastly, the + rail's need a bridge wire. In the pic above I added a fairly large gauge (I forget now). But they will see a large current across them. They will burn out if not large enough. I used resistor legs to join the caps in the picture above, but I'd recommend at least a 16AWG solid core. A 65W RSX can generate 55 Amps. That's why it has 2 phase power. Each IOR power block can deliver a maximum of 40A. So it takes 2 of them to diliver the required power. The CELL CPU has 3 phases. I'm not sure how many watts it pulls, but guess around 100 Amps. That needs to be cunducted across the + rails, which will burn right through thin gauge wires. I looked it up, you would need 4x 8 gauge AWG wires to meet the 24A they could see at peak load. 8 guage is super thick. It's probably fine to go smaller, but I would just stick to my board for convenience. I made the + rail as wide as possable and the 0.8mm double thick copper is more than enought to handle any current demad the PS3 could need.