0 mph VSS - 10 volt DC on output????
10-26-2009, 07:21 PM
#1
0 mph VSS - 10 volt DC on output???? Hey guys, I'm putting a 8.1 using a 2000-2002 truck dbw harness and computer into a 69 Vette.
Went through great lengths to install a 40 tooth 4L80E reluctor in my Richmond six speed with a VSS sensor so I could get a quality speed signal. Also hoping to use the dbw cruise control.
Okay...on my snap on scanner, I'm reading 0 mph when the wheels are turning.
I jumped into the harness and checked AC volts coming off the trans - I'm getting a stead up and down volt feed as the speed increases/decreases.
However, when I check my OUTPUT (to speedometer) - I'm getting 10 - 11 volts DC.
With the car sitting still and engine off (ignition on) - I'm getting 10.5 volt DC out of the speedometer OUTPUT to gauge.
??????
Sound like a programming glitch or a bad PCM or ????????
I checked the schematic - all wires are in the correct ports.
??????????
Went through great lengths to install a 40 tooth 4L80E reluctor in my Richmond six speed with a VSS sensor so I could get a quality speed signal. Also hoping to use the dbw cruise control.
Okay...on my snap on scanner, I'm reading 0 mph when the wheels are turning.
I jumped into the harness and checked AC volts coming off the trans - I'm getting a stead up and down volt feed as the speed increases/decreases.
However, when I check my OUTPUT (to speedometer) - I'm getting 10 - 11 volts DC.
With the car sitting still and engine off (ignition on) - I'm getting 10.5 volt DC out of the speedometer OUTPUT to gauge.
??????
Sound like a programming glitch or a bad PCM or ????????
I checked the schematic - all wires are in the correct ports.
??????????
10-26-2009, 10:51 PM
#2
How is the speed sensor wired into the PCM? The VSS should be wired to RED PCM pins 20,21. Make sure nothing else is on those circuits. I helped with a swap recently, and they tried to hook an autometer programmable speedometer into the purple signal wire, this killed the signal to the PCM.
The VSS outputs the PCM generates for the instrument cluster, etc, are DC square wave. I would expect to see a positive DC voltage there, even sitting still. It would be hard to decipher anything from just a DC volt reading on the VSS output wire.
What kind of air gap do you have between the tip of the speed sensor and the 40 tooth wheel? About .020-.030 should be about right.
where is the 4l80e ring located in the manual trans? I thought the 4L80E sensor ring was about 4-5 inches in diameter, and was pressed onto the rear planet in the 4L80E's.
The VSS outputs the PCM generates for the instrument cluster, etc, are DC square wave. I would expect to see a positive DC voltage there, even sitting still. It would be hard to decipher anything from just a DC volt reading on the VSS output wire.
What kind of air gap do you have between the tip of the speed sensor and the 40 tooth wheel? About .020-.030 should be about right.
where is the 4l80e ring located in the manual trans? I thought the 4L80E sensor ring was about 4-5 inches in diameter, and was pressed onto the rear planet in the 4L80E's.
Last edited by busta9876; 10-26-2009 at 10:56 PM.
10-27-2009, 05:07 AM
#3
It is wired correctly - I verified 20/21 on the red connector - I also verified the output is coming from the correct port (I think it is 40 - I don't have my cheat sheet in front of me t the moment).
There is nothing else tagged into the VSS along the way. All the wires ohm out clean.
Sound like a bad program or PCM? If so...any other way I can check that?
There is nothing else tagged into the VSS along the way. All the wires ohm out clean.
Sound like a bad program or PCM? If so...any other way I can check that?
08-29-2017, 06:45 PM
#5
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I'm having the same problem! hey there buddy! I just wanted to know what was the outcome on your problem? I'm having the same issues. Everything checks out good but hptuners reads 0mph. Even my speedo works perfectly
09-01-2017, 06:20 AM
#6
TECH Addict
If you go to lt1swap.com the have the wiring pin out. On mine red connector pin 20 and 21 are the inputs from the tranny 5 speed manual and red connector pin 50 is the output to the speedo.
