97 Saturn VSS issues

[Leino]

Recently swapped motors in my 97 sc2 manual dirt track car and having issues with the VSS, it seems to only have one wire coming from it and the other prong is plugged off? Everywhere I see it should have a purple and yellow wire to the PCM. Does anyone have a wiring diagram or advice on what I need to do to get it working? Having a neutral rev limiter in gear is not ideal while dirt track racing. Thanks!

[fetchitfido]

Sensor should read 800-1600ohms across the terminals.
Not sure how you'd fake a signal to the PCM but AllData says it's a square wave 0-12vdc and 5000ppm.

[billr]

I question if Alldata is correct about it being a 12V square-wave. I'm pretty sure the VSS is a variable-reluctance (VR) sensor and puts out a wave more like a sine, with amplitude varying with speed.

I also doubt the output is 5000 ppm, if "ppm" means pulses-per-mile. A quick-and-dirty calculation indicates 5000 ppm would mean a diff ring-gear with only about six teeth; not realistic. Or, does the VSS sense something other than ring-gear teeth???

[ultravioletnk]

Originally Posted by billr

Or, does the VSS sense something other than ring-gear teeth???

there is a reluctor ring on the diff for the vss, it definitely has more than 6 teeth though. you can see it in this pic someone on sixthsphere posted of the aftermath of a diff pin failure. the vss does not sense the teeth on the ring gear.

[ultravioletnk]

Originally Posted by Leino

Recently swapped motors in my 97 sc2 manual dirt track car and having issues with the VSS, it seems to only have one wire coming from it and the other prong is plugged off? Everywhere I see it should have a purple and yellow wire to the PCM. Does anyone have a wiring diagram or advice on what I need to do to get it working? Having a neutral rev limiter in gear is not ideal while dirt track racing. Thanks!

that sounds like you may have gotten the connectors mixed up between the vss and oil pressure switch. i'm 99% certain they use the same connector. i'm curious, does the "genie lamp" (oil pressure light) come on when the key is in run without the engine started, or is it just the "drunken robot" (battery light)? you are correct that there should be two wires for the vss, purple and yellow.

[billr]

Yeah, looks like about 16 teeth in that picture.

[fetchitfido]

I really really hate the electronic GM FSM I have. If it has the same info as AllData, it's buried under stupid crap and/or not accessible in both locations of the manual that make sense. Started looking under the automatic trans info stuff because the manual section just had how to replace the VSS and no where had "how the VSS works or is used."

Originally Posted by '01 SC2 automatic from GM FSM

The output speed sensor (OSS) produces an AC voltage of different amplitude and frequency depending on the velocity of the output shaft. The OSS produces the signal from 16 evenly spaced machined notches on the transaxle differential carrier. The OSS produces a readable AC voltage signal when vehicle speed is above 5 km/h (3 mph). This OSS signal is sent to the PCM, which is used to determine the velocity of the output shaft.

The PCM uses the OSS to monitor the speed of the output shaft. In conjunction with the ISS, the PCM can determine the slip across the commanded gear clutch pack. The PCM can use this information to determine the actual gear ratio, gear slippage or lack of main line hydraulic pressure.

Seems to indicate the AllData info I posted before is wrong, but the AD was linked from the '97 SC2 manual trans section and this "new" part is from a '01 DOHC automatic. If the same VSS/OSS part number is used on '97 and '01 then I'd believe GM over AllData.

[Waiex191]

Those "teeth" are what pumps the oil, I believe.

[Leino]

Originally Posted by ultravioletnk

that sounds like you may have gotten the connectors mixed up between the vss and oil pressure switch. i'm 99% certain they use the same connector. i'm curious, does the "genie lamp" (oil pressure light) come on when the key is in run without the engine started, or is it just the "drunken robot" (battery light)? you are correct that there should be two wires for the vss, purple and yellow.

I’ll have to double check those connectors, I’m working out of town for a while so it’ll be a little bit til I can get back to it. Hopefully it’s something as simple as switching them over. Would both of them have the “mushroom” style look to them?

[fetchitfido]

I don't think the oil pressure line will reach to the VSS without a lot of work. Probably possible...I got the A/C compressor wire and O2 sensor wire mixed up on a '93 once and spent a few weeks wondering why I was getting 17mpg.

If those 2 are the same connector then you might have mixed up the knock sensor as well, I don't remember what year they changed that connector but I did have to change it for another style once.

[ultravioletnk]

Originally Posted by Waiex191

Those "teeth" are what pumps the oil, I believe.

they do also serve that purpose, along with the ring gear. however, that is without a doubt the vss reluctor ring, you can clearly see that it's aligned with the vss if you have the transmission disassembled. you can also see it if you remove the vss and look down the bore with the transmission assembled. another note, the 5000 pulses per mile number is correct according to the fsm.

Originally Posted by Leino

I’ll have to double check those connectors, I’m working out of town for a while so it’ll be a little bit til I can get back to it. Hopefully it’s something as simple as switching them over. Would both of them have the “mushroom” style look to them?

yes, i also checked the connector end views and they are the same connector. here is the oil pressure switch connector, and here is the vss connector. i'm very confident that's your problem.

Originally Posted by fetchitfido

I don't think the oil pressure line will reach to the VSS without a lot of work. Probably possible...I got the A/C compressor wire and O2 sensor wire mixed up on a '93 once and spent a few weeks wondering why I was getting 17mpg.

If those 2 are the same connector then you might have mixed up the knock sensor as well, I don't remember what year they changed that connector but I did have to change it for another style once.

it actually reaches very easily, i've almost made that mistake myself a couple times which is why it came to mind so immediately. consider that the wiring harness wraps over the top of the transmission clutch housing, and the oil pressure switch and vss are relatively equidistant from that point. the knock sensor uses a different (single-pin) connector entirely. they did change it, i believe somewhere around '96, but i've found it easier to just swap the sensor rather than modify the wiring harness.

i did have to make an adapter for the tps connector on rings when i swapped the '99 engine in, but i just broke apart an old tps for the connector and soldered on the newer style tps connector off a junkyard harness. i really try not to chop up wiring harnesses if i can reasonably avoid it. that said, i have swapped newer map sensors onto a couple of my cars (not that i think it's made much tangible difference, i just figured the newer map sensors might be more accurate) and for those i did cut off the stupid weatherpak connector where the tab always breaks off and splice in the newer style connector.

[billr]

All manuals, including the Saturn FSM, may contain errors. You have to temper use of manuals with common-sense. My 195-60 x 15 tires roll about 832.7 turns per mile. Multiply that by 16 teeth and you get 13,323 pulses-per-mile. Yes, other tire sizes were options for our Saturns, and that 832.7 is subject to inflation pressure, but 13K is a long way from 5K...

[ultravioletnk]

Originally Posted by billr

All manuals, including the Saturn FSM, may contain errors. You have to temper use of manuals with common-sense. My 195-60 x 15 tires roll about 832.7 turns per mile. Multiply that by 16 teeth and you get 13,323 pulses-per-mile. Yes, other tire sizes were options for our Saturns, and that 832.7 is subject to inflation pressure, but 13K is a long way from 5K...

i see your point. the only other mention i can find of the vss operation is this page on the automatic transmission. the 5000 number may indeed be incorrect.

... that said, i just fired up the fsm virtual machine i have (which i'm working to get posted on my site) and selected a 2002 sl2... it clearly states "The OSS produces 5,000 readable pulses/mile between 5-161 km/h (3-120 mph), which are sent to the PCM to determine vehicle speed. The vehicle speed input is used to determine the miles the vehicle has traveled. The PCM reads the OSS signal and sends vehicle speed information to the BCM over the class 2 link. The BCM in turn calculates the distance traveled and sends the information to the I/P cluster over the link. The I/P cluster increments the electronic odometer accordingly."