Hello I will help you with your question,
The O2 UP and O2 DOWN fuses are fed from the main relay contact which also feeds the INJECTOR fuse so if you have power to the injector fuse the main relay is closing and the fault is between the main relay and the fuses.
If you do not have power to the injector fuse then the main relay may not be closing.
Does the van run?
If there is a problem between the main relay and the fuses the FAM (Front Area Module/fuseblock) will need to be replaced.
Check for continuity with the battery disconnected between the main relay contacts and the O2 fuses. Seee the diagrams below for locations. Follow the "D" arrow from the main relay to the O2 fuses
Let me know what you find
You do use an ohmeter to check for continuity,
Pull the main relay and look at it, find pin #87 and measure that pin socket for voltage, if you have 0 volts then switch to ohms and measure between pin socket #87 and both of the O2 fuses.
You should have 0 ohms or close to it.
The main relay is the large white one and should be marked on its side or bottom with the pin numbers.
What you are looking for is an open in the FAM (fuse block) if it is open you will have to replace the FAM.
You can just pull the main relay, you caught me on the way to bed so if you are going to be working on this tonight all you have to do is see if you have a complete circuit between the #87 pin of the relay and the two O2 fuses. If you do not have a complete circuit then there is an open inside the fuse block and the fuse block will have to be replaced.
I am not sure where you are measuring the 12 volts from pin #87 to the O2 fuses?
Does pin socket #87 have voltage with the main relay removed? If so how about pin socket #30 on the relay?
You should not have power on the relay pin socket with the relay removed. The O2 fuses are fed when the relay closes so we need to be certain of the readings. The FAM is expensive so measure twice.
Once you have the relay socket identified according to the second diagram I posted above then use your Ohmeter to see if you have the same reading between that pin socket and the O2 fuses as you have when you touch the meter leads together.
Let me know so we can confirm if you need a fuse block
Ok if you have no voltage on the pin socket #87 and have a complete circuit to the fuses then you need to check the fuses again for voltage with the engine running. You can also test the Injector fuse for power to verify that the main relay is closed but the engine will not run with the main relay not closing so you have to have power tot he injector fuse but the injector fuse and the O2 sensor fuses all are fed power from the same point off pin #87 (shown as "D" in the wiring diagrams) so they all should have power with the enginne running.
I suspect that you are not measuring correctly.
You need to put one of the meter leads on a clean ground, battery negative terminal is best. The other lead is used to probe for voltage, start at the positive post of the battery to confirm the meter is working (the leads do break over time) and with the meter set to DCvolts you should see 12.6 volts at the battery with the engine off.
This is why I prefer a 12 volt testlight for simple voltage tests.
If the fuse is hot then a reading of 0 volts with the leads on both pins on the back of the fuse would indicate that the fuse is good but if there is no power to the fuse it would indicate nothing so you have to estabilish that you have power to the fuse first
It sounds like you have power to the O2 fuses so check at the O2 sensors. So what code are you getting again?
OK your next place to check for voltage is at the sensor connector, check for resistance of the heater element in the sensor (about 10 ohms) then make sure you have a continous piece of wire back to the PCM.
Let me know how i can help
Concentrate on finding voltage and ground at the sensors.
Check the blue wire at each sensor connector for power to a clean metal ground with the key on, next move the meter lead from the metal ground to the pink or pink/black wire which provides ground from the computer. You should have the same reading.
Let me know what you get
DO NOT MEASURE ANY WIRES EXCEPT THE ONES I DESCRIBED YOU CAN DAMAGE THE COMPUTER!
The upstream sensors will have the same setup as the down stream so you should have the same readings. There is one sensor that has a pink/black wire rather than the pink so use that one. All the sensors have the blue power wire.
Once you measure the power and ground at each sensor harness side move to the coresponding pins on the sensor side of the connector and measure resistance. DO NOT MEASURE RESISTANCE ON ANY OTHER PINS YOU CAN DAMAGE THE SENSOR!
Let me know if you find anything that does not show power and ground on the harness side or is out of range on the sensor side.
The sensors should have some kind of resistance from where the blue wire and the pink wires would plug in so make sure you are on the right pins on the sensor connnector and are you seeing 0.0 or OL for the reading. Test by touching the tips of the meter leads together. This is a digital meter?
Ok the down stream should have the same readings as the upstream so the heaters are open in the downstream sensors.
Sorry but the only thing you can do is replace the sensors.