Skip Posted January 20, 2007 Share Posted January 20, 2007 My VSS#2 drive gear (the one inside the front diff) is toast. CEL is on as a result and I need the car inspected. Will not pass OBD2 inspection with the CEL on. I'm an old dumb fart and it's too cold to yank the lump / tranny. Thanks for a link from Tech1967 I saw this http://www.vanbran.com/bug/images/conversion9/vss_pickup3_l.jpg It is a reed switch mounted simply on a strip of metal. The reed switch will be triggered by a ring of magnets fastened around the DOJ http://www.vanbran.com/bug/images/conversion9/vss_magnets1_l.jpg I'll add subtract magnets to get the speedometer about correct. Leaving the FWD fuse in prevents the AWD engagement. This should fool the ECU into thinking it has a VSS input - eh? What a Rube Golberg?? Flame retardant undies in place. Link to comment Share on other sites More sharing options...
nipper Posted January 21, 2007 Share Posted January 21, 2007 this will get you through inspection, but it is going to royally screw up your AWD. Basically you wont have any. The TCU uses the two speed sensors to determine front and rear axle speeds, and adjusts acordingly. If both sesnors are going at the same speed all the time, you wont get more then 10% of the power sent to the rear. The VSS is a magent that creats a pulse as the signal wheel goes by. There may be no power there to speak of to send a signal. Also be very careful, as things like this is how computers go poof. Also a reed switch sends a very spikey and dirty signal to the ecu, again that can do damage. nipper Link to comment Share on other sites More sharing options...
hankosolder2 Posted January 21, 2007 Share Posted January 21, 2007 My VSS#2 drive gear (the one inside the front diff) is toast. CEL is on as a result and I need the car inspected. Will not pass OBD2 inspection with the CEL on. I'm an old dumb fart and it's too cold to yank the lump / tranny. Thanks for a link from Tech1967 I saw this http://www.vanbran.com/bug/images/conversion9/vss_pickup3_l.jpg It is a reed switch mounted simply on a strip of metal. The reed switch will be triggered by a ring of magnets fastened around the DOJ http://www.vanbran.com/bug/images/conversion9/vss_magnets1_l.jpg I'll add subtract magnets to get the speedometer about correct. Leaving the FWD fuse in prevents the AWD engagement. This should fool the ECU into thinking it has a VSS input - eh? What a Rube Golberg?? Flame retardant undies in place. I think it will work fine if you can get the magnet spacing right. The "spiky" signal Nipper is referring to is contact bounce (i.e. the reed switch contacts do not create as neat a pulse as the solid state hall effect VSS sensor.) However, contact bounce will not damage the ecm, simply because the switch is driving a non-inductive load. (What he said would be 100% right if you were switching a solenoid, a motor or other inductive load.) Contact bounce COULD cause strange or erratic operation, but it shouldn't damage anything. You may need to use a pull up or pull down resistor with the reed switch (I didn't look at the link to see if that's included.) I may have a better idea...why not drive the VSS2 sensor off the other VSS sensor? I.e. float the +5 and ground wires to the front sensor, then connect run a wire so it gets pulses from the rear sensor. (this is assuming that they normally output the same number of pulses per wheel revolution.) I think this will fool the ecm and should be fairly low risk. (but don't come knocking on my door if you jazz the car up!) Of course, FWD fuse must be in... Plan "C" -register the car at an address which is not subject to vehicle inspection. Good luck, Nathan. Link to comment Share on other sites More sharing options...
Skip Posted January 21, 2007 Author Share Posted January 21, 2007 Thanks for the encouragement Nip, I guess in your rush to add something you missed the part about the fuse in the FWD holder. To answer your noisy switch comment. I, for reasons of simplicity, left out the fact that I will incorporate a type of Schmitt trigger using an IC 555 in mono stable mode. This will be filtered through a Brokaw bandgap style filter thus proving a bounce free output very similar to the output of a Hall effect switch. Which most know is what the oem VSS is. I may be wrong but this simple bench work will be much easier than pulling the tranny. I thank you humbly for taking the time to respond. Link to comment Share on other sites More sharing options...
Skip Posted January 21, 2007 Author Share Posted January 21, 2007 Thanks for the idea Nathan (guess we posted almost at the same time). I do suspect the VSS# 1 output is the same as #2. I believe the ECU uses #1 if #2 is absent. I would like a semi working speedometer and your idea would provide it. The closest county without the emission inspection is about .75 click from where I live - thanks for your reply and that may be an option. Link to comment Share on other sites More sharing options...
nipper Posted January 21, 2007 Share Posted January 21, 2007 Ok so it sounds like you understand how things work YEs when one VSS is dead, the other takes over, but you loose AWD. Loose both VSS and the car goes into limp mode. nipper Link to comment Share on other sites More sharing options...
hankosolder2 Posted January 21, 2007 Share Posted January 21, 2007 Thanks for the idea Nathan (guess we posted almost at the same time). I do suspect the VSS# 1 output is the same as #2. I believe the ECU uses #1 if #2 is absent. I would like a semi working speedometer and your idea would provide it. The closest county without the emission inspection is about .75 click from where I live - thanks for your reply and that may be an option. Let us know if "doubling up" the VSS sensor works. I'm curious! Nathan Link to comment Share on other sites More sharing options...
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