Testing speedometer or vss circuit Issue?

[Packard]

SYMPTOMS Was driving freeway speedometer dropped to 0 then


I need help to test the car
I have dvom Ive used one but unsure THE Steps on testing the speedometer or the vss .


Quotes from another post stated Im also refering to my all data info about the sensor
Im picking info from whereever I can get it so I can troubleshoot the speedometer get it fixed Need help to figure it out.
[IMG][/IMG]
Your Vehicle: 1995 Saturn Sedan L4-1.9L SOHC VIN 8

Vehicle » Sensors and Switches » Sensors and Switches - Powertrain Management » Sensors and Switches - Computers and Control Systems » Vehicle Speed Sensor » Service and Repair


Service and Repair


Mounting Of Vehicle Speed Sensor.


VEHICLE SPEED SENSOR (VSS)

REMOVAL

WARNING: Make sure the vehicle is properly supported and squarely positioned prior to lifting.
Position vehicle on lift and raise vehicle.
Disconnect electrical connector from VSS.
Remove VSS.
INSTALLATION

Install vehicle speed sensor.
Connect electrical connector to VSS.
Lower vehicle.

The below info on yellow is return and purple is return Im not certain Im going to need more literture to verify that is the case.

The purple wire on the Vss circuit is the return to the Trans, and the yellow is the one reporting the speed to the PCM. YEAH! Thank you Chilton for begin accurate in the diagrams.


VEHICLE SPEED SENSOR The vehicle speed sensor (VSS) is a variable reluctance pulse generator that senses the transaxle output

A speed sensor. Courtesy of General Motors Corporation, Service Technology Group.
A defective vehicle speed sensor may cause different problems depending on the computer output control functions. A defective vehicle speed sensor (VSS) may cause improper converter clutch lockup, improper cruise control operation, and inaccurate speedometer operation.

Prior to VSS diagnosis, the vehicle should be lifted on a hoist so the drive wheels are free to rotate.
Backprobe the vss output wire and connect the voltmeter leads from this wire to ground.
Select the 20-volt AC scale on the voltmeter.
Then start the engine.
Place the transaxle in drive and allow the drive wheels to rotate. If the VSS voltage signal is not 0.5 volt, or more, replace the sensor.
When the VSS provides the specified voltage signal, backprobe the VSS terminal at the PCM and repeat the voltage signal test with the drive wheels rotating.
If 0.5 volt is available at this terminal, the trouble may be in the PCM (powertrain control module).
When 0.5 volt is not available at this terminal, turn the ignition switch off and disconnect the wire from the VSS to the PCM.
Connect the ohmmeter leads across the wire. the meter should read zero ohm.
Repeat the test with the ohmmeter leads connected to the VSS ground terminal and the PCM ground terminal.
This wire should also have zero ohm resistance. If the resistance in these wires is more than specified, repair the wires.
The condition of a speed sensor can be checked by going through the diagnostic routines for the system.
If this test indicates that a sensor is faulty, the sensor should be replaced.
Speed sensors can also be checked with an ohmmeter. Most manufacturers list a resistance specification.
The resistance of the sensor is measured across the sensor's terminals.
The typical range for a good sensor is 800 to 1400 ohms of resistance.

[Packard]

Purpose:
The vehicle speed sensor (VSS) is a variable reluctance pulse generator that senses the transaxle output.

Operation:
It operates between 0-161 km/h (0-120 mph).

The VSS informs the PCM of vehicle speed.

The PCM uses VSS input to provide vehicle speed to the instrument cluster for the speedometer. On vehicles equipped with cruise control, this signal also goes to the cruise control module and PCM.

[Packard]

I have a bouncy speedmeter. Its done this long time ago but it fixed itself not sure what to make of it . Im not 100 percent but I want to replace the sensor . What do you guys think I should do with a bouncy speedmeter 1min Im reading 60 then Im reading 0 then it goes back to 60 wtf is this???

[Waiex191]

I would guess a bad stepper motor in the cluster. But wait for the more knowledgeable folks to show up.

[Packard]

This is the issue I experience last night going down freeway Speedometer drops to zero then back to normal speed while driving on freeway was about 55-65 mpg when it happened. It freaked me out cause Ive never have issues with my car . Im unsure what I should do next . I can get vss on amazon here in 2 days. But not 100 percent . cause some say 1 other say other. confusing. I have dvom tool for probing . If i had a scanner I definitely do a scan but Im not sure where to get one that cost me damn kidney.

[Packard]

if its a steeper I wonder if I did some rattling with the cluster like tapping it make it work again???

[OldNuc]

Not a stepper motor. Can be replaced but is not simple either. Most likely cause of failure is either a loose connection at the cluster connector or failing odometer gears. The spedometer and odometer are run from the same board. A vss failure will almost always set a SES light immediately. The 95 is a bit unique so the easy first fix would be replace bothgears and then if that is not it replace the cluster.

If you have an auto trans a VSS failure will instantly confuse the trans and you will feel it.

[billr]

Wow, this thread started out "in the weeds"! Images of a V-8 and what looks like valve rockers/lifters of something else? Those have nothing to do with this Saturn VSS/speedo problem.

Don't throw any parts at it yet. Don't even bother with the DVOM yet. Answer the few questions already implied above: Does this have an auto trans? Does the cruise control work? Are there any codes set?

[billr]

Maybe off-topic, but the images at the beginning of this thread change every time I open it! None so far pertain to the VSS/speedo, probably not even Saturn.

[Packard]

I have no codes and no lights for vss . vss seems to be working causing tranny would have shutoff and not move cause a solenoid wont shiff if the vss sensors quits. Id dont have any shift problems.

When I first got this car the Cruise worked.
Now the cruise does not work
Ive got brake lights so the brake switch is working for cruise circuit. Not sure what could fail cause I dont have any lights.
Cruise dont work
so is that a bad cruise control switch ??


So Im thinking I have bad gear in the dash cause I did a check of the speed in car I took a app on phone that measures speed and speedometer was accurate . So its getting signals .

Anyone know how to check the cruise control ?? I know u have to have a working brake and clutch switch . Those apparently must be working cause it would not start without a clutch switch and brake I would not have lamps.

[OldNuc]

If you are reffering to the 95 in your profile the cruise is almost all self contained in the big brick on the side of the column. The most likely external failure other than a bad fuse is the clutch switch. It is located so it contacts the clutch pedal arm with the pedal is UP, it has noting to do with starting either.

The drawing and further info is in this thread: http://www.saturnfans.com/forums/sho...d.php?t=201996

[Packard]

yes but if u read my previous post I stated that my car starts and runs fine . And both the clutch switch would have to function for a car to start. Which in my case it does.
So Im thinking it has to do with a ground or 12 volts not reaching the module.

Symptoms of a Bad or Failing Clutch Switch
Engine does not start.

[billr]

I'll ask again... is this a manual trans or automatic trans? If you answered previously, I didn't find it; my apologies.

You can't conclude the VSS is OK because the car can be driven; especially if it is a manual trans. No codes? a good "sanity check" would be to disconnect the VSS (or just about anything else) and seeing if a code does get set that you can actually find/read).

There has been talk so far about both a clutch switch applicable to only a manual trans, and solenoids which only apply to the auto trans. I, for one, will continue to be "in the weeds" until it is clear what type trans this has.

[OldNuc]

Originally Posted by Packard

yes but if u read my previous post I stated that my car starts and runs fine . And both the clutch switch would have to function for a car to start. Which in my case it does.
So Im thinking it has to do with a ground or 12 volts not reaching the module.

Symptoms of a Bad or Failing Clutch Switch
Engine does not start.

There are 2 clutch switches, The one that lets you start the car is NOT associated with cruise in any way. The cruise disable switch(clutch switch) is located so it contacts the clutch pedal arm when the pedal is full up.

[Packard]

i stated that in prior post