You may want to try a wreckers to get the reservoir with the sensor or just the sensor.

 

I think that this would be your best (least costly) bet. I don't how different the brake fluid resevoirs are from a '04 RAM 2500 and a '06 RAM 1500 but the sensor on my 2500 was fairly easy to remove (and replace) from where it fits in the brake fluid resevoir. I inadvertantly dislodged mine while changing my fuel filter. When I was finished changing the fuel filter I found the sensor (a small circuit board at the end of a pair of wires) free-floating in the engine compartment. I had not noticed it before I started the job and it took a fair amount of time to figure out what it was and where it went. There was a part # printed on it so I "googled" the number to find out what it was. Came back as the brake fluid sensor. Once I knew what it was pretty easy to narrow my search RE: where it went. To be completely honest, it doesn't look like it was meant to be routinely replaced. I found a hole in the side of the fluid resevoir and it snapped right into place. Problem solved.
So, as stated above, check out your local salvage yard. You might have to buy the complete resevoir assembly but maybe you could just "harvest" the sensor. I'm sure it will be a lot less than $500!!! Good luck.
RipVan

 

Unplug the sensor maybe? If that doesn't do it ground the sensor wire, has to be one or the other.

 

didnt know our trucks had this sensor.

 

I tried unplugging and that didn't seem to work. I also put a wire on the end of the plug into each "hole" to ground it out and that didn't seem to work either.

 

The sensor may have a resistive value.

 

Go to rockauto, they will have what you need for much less than the crazys at the dealer would love for you to pay.

 

I looked at rock auto and they only had the whole brake assembly listed.

 

Odd......well you should be able to find a reservoir just about anywhere, the 3rd and 4th gens use the exact same master and booster setup

 

Yeah, I looked at rockauto and they just had the whole mastercylinder also. No sensor and no just resevour. But you could buy a master cylinder with no resevour. I could try a junk yard but otherwise I can't find a place that sells just the sensor.

 

I also have a problem with the ABS/BRAKE lights being lit on the dash. The ABS sensor on the rear axle does not appear to be the problem since it shows the proper resistance of 1.8K ohms. So, I started looking at the sensor that is underneath the brake fluid reservoir. It shows an extremely large resistance / open circuit. So, I tried putting a 1K ohm resistor across the connectors in the socket that is on the cable that connects to the bottom of the reservoir while the cable was not connected to the sensor. It turns that this will turn off the ABS/BRAKE warning lights. The ABS sensor on the rear axle is 1.8K ohm, IIRC, but I did not have that value handy to do a test with. I did have some 1K resistors already out since I was working on an Arduino project, so I figured I would just give one of them a try to see if it made a difference. Of course, it doesn't *fix* the problem, just kind of masks the problem. But, it does give me a bit of data to indicate that the problem is probably that sensor instead of a wiring issue. A wiring issue would probably be a bigger pain to trace down.

I'm not sure what the resistance for a good sensor should be. If someone has a multimeter handy, could they try measuring the resistance across the two pins at the bottom of the reservoir with the plug removed? Thanks...

 

Go get a second opinion cuz I wouldn't trust most mechanics.

 

Why do so many people comment giving their useless opinions, he asked a simple question that has a simple answer. Is there a way to bypass the sensor and the answer is yes. If its a brake fluid switch you put a jumper wire from wire to wire or simply unplug it, its one or the other. If its a brake fluid SENSOR you need to unplug it and put a 10k ohm resistor from wire to wire Youre welcome