Craig or Lance... stand alone sensors...

[Supercharged408]

I have a FAST system that was setup for a Dakota. The system used the stock sensors but did not remove them from the stock computer, so basicaly you get the stock ECU to read coolant and air temp as well as the FAST. One document I had sais the FAST was modified for this to work. I work on this kind of things for the OEM's quite often, and figure what was modified was the pull up resistors were removed since they were already in the stock ECU, is this correct? If so, can I add the pull up resistors to the FAST, what size should I use and what resistor holes on the board could I solder them to?

What I get as a sensor readout since I have no oem ECU in the loop and now use GM sensors is 255 degrees when the sensors are plugged in, and about 81 degrees when the sensors are not plugged into anything.

I am trying to get this thing working today, so if anyone has info ASAP, I would greatly appretiate it.

Damon

 

[Evil RT]

you should step up to the Accel DFI, and stop playing around





Scott

 

[Supercharged408]

Already done PUNK! ;-)

Damon

 

[bobc455]

Pretty sure that those sensors are resistive, and so if you have them wired in parellel between the two computers (do I understand what you're doing correctly?), you may be confusing all of the electronics. I don't think you can have two seperate sources checking resistance at the same time. If I were trying to do that, I would have only one ECM per sensor, which means you'd have to get a second sensor and leave them independantly wired.

Maybe I'm wrong...

-Bob C.

 

[Supercharged408]

I think ya got my situation backwards. The system for the Dakota is setup to run in congunction with the stock PCM. This way, it allows the stock enging controller to keep reading its own sensors, and then the FAST also reads those sensors. That is how it is setup from FAST. I do not like it that way and want to run it seperate (FAST gets its own dedicated sensors) The way a computer reads sensors is that it compares a voltage, basicaly, the signal line is tied through a resistor to either 5 or 12 volts AKA a pull up resistor. This way, when the signal comes in, the ECU has a way to decifer that signal. If FAST setup their hardware (in the DAKOTA) to read off a sensor that is already pulled up, they would simply remove the pull up resistors for those sensors. The solution (I think) is to put a resistor in the line between the signal and the 12V line. I just want to know what resistance I should use, commonly a 1K ohm resistor is used.

Damon