91 Chev. S10/T10 Automatic 4WD - Electronic Speedometer was intermittently not working, now it's not working at all. Because I couldn't find a speedometer cable at all, I took the instrument cluster out, and took it to a specialty shop to have the speedometer repaired, I now know the expensive way to find out that it was not the Speedometer in the instrument cluster. According to some internet sights, there are 3 other thinks to check for, 1) fuse 2) VSS 3) DRAC. Checked fuese with light probe, they seem to be find. I cannot located the VSS, its suppose to be located on the tailshaft, driver's side, however in lieu of a tailshaft I have a transfer case, and I cannot seem to find any electrical connections to it. Does anyone know for sure where the VSS is for this model & make? And just so that I know, does anyone know where the DRAC is located as well? I have a repair manual but it seems to skip any inforamtion regarding the VSS and the DRAC.
VSS was located on the tailshaft of the Transfer Case, Drivers Side.
ECM - remove panel that is below Glove box, ECM is located just above it.
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.
1991 Chevy S-10 / T-10 Blazer 4WD AutomaticVSS was located on the tailshaft of the Transfer Case, Drivers Side.
ECM - remove panel that is below Glove box, ECM is located just above it.
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.
99% of the time, the Speedometer doesn't work because the VSS (Variable Speed Sensor) stops working. The VSS on a 2WD is located on the tailshaft of the transmission, drivers side. On a 4WD the VSS is located on the tailshaft of the Transfer Case, drivers side.
You will need a 1" socket to remove this sensor. All sockets come as either a 6 point or a 12 point, these are the number of angles in which to lock on to its recepticle, for this purpose a 12 point socket is prefered.99% of the time, the Speedometer doesn't work because the VSS (Variable Speed Sensor) stops working. The VSS on a 2WD is located on the tailshaft of the transmission, drivers side. On a 4WD the VSS is located on the tailshaft of the Transfer Case, drivers side.
You will need a 1" socket to remove this sensor. All sockets come as either a 6 point or a 12 point, these are the number of angles in which to lock on to its recepticle, for this purpose a 12 point socket is prefered.
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Did you have it check for DTC'S - diagnostic trouble codes ?
Speedometer
The speedometer is an analog gauge that is located in the instrument cluster. The PCM/VCM receives an analog input from the vehicle speed sensor and converts it to a digital signal containing 4,000 pulses per mile (PPM) for the instrument cluster.
The PCM/VCM sends this digital output (4,000 PPM) to the instrument cluster on a designated circuit. These pulses can be measured in Hertz (Hz) using a digital multimeter (DMM) on the AC scale. The PCM/VCM calibration is matched to the final drive and tire size of each vehicle. If the final drive or tire size is changed for any reason, the PCM/VCM must be updated in order to match the new final drive or tire size. If not, the signal will not be accurate for proper speedometer/odometer operation. An incorrect signal can affect the antilock brakes and the cruise control systems.
The speedometer system consists of the instrument cluster, vehicle speed sensor (VSS), PCM/VCM and related wiring. The VSS is a permanent magnet signal generator that sends an analog signal proportional to the propeller shaft speed to the PCM/VCM. The VSS mounts to the transmission tailshaft extension housing on 2-wheel drive (2WD) models and the transfer case output shaft housing on 4-wheel drive (4WD) models.
Repairs to the instrument cluster can only be performed by an authorized instrument cluster service center.
DTC P0502 Vehicle Speed Sensor (VSS) Circuit Low Input and DTC P0503 Vehicle Speed Sensor (VSS) Circuit Intermittent in Automatic Transmission - 4L60-E
- DTC P0500 Vehicle Speed Sensor (VSS) Circuit in Engine Controls - 4.3L
Important: If the instrument cluster is completely inoperative, refer to Instrument Cluster Inoperative .
Install a scan tool.
Raise the vehicles drive wheels. Refer to Lifting and Jacking the Vehicle in General Information.
Start the engine.
Place the transmission into drive for automatic transmission and third gear for manual transmission.
Compare the displayed vehicle speed on the Instrument Cluster with the monitored speed on the scan tool.
Does the vehicles speedometer and the scan tool both display 0 km/h (0 mph)?
You really need a Factory scan tool or equivalent to check this . The VSS is an input to the PCM/VCM . engine computer . You can test with a DVOM - digital volt ohm meter , for signal to engine computer .
I know most people don't like hearing this , but I suggest you take it to a ASE certified repair facility .
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not a good idea to do a voltage test on a computer component, it can result in damage to the ECM. if only the speedometer is not working and the other gauges do work, the first place to start is the speed sensor, it is the most common issues with inoperative speedometers.
If your speedometer is not electronic, unfasten the speedometer cable from the back of the dashboard instrument assy. Replace the odometer & speedometer unit with another one. Reconect the speedometer cable. This should do the trick.
I have a 91 Accord. When I purchased it, the speedometer did not work. I replaced the VSS (Vehicle Speed Sensor) and the speedometer started working again. I paid $24 for the sensor on ebay. The local part stores wanted $150. It's an easy fix. It takes about 20 minutes to replace.
VSS was located on the tailshaft of the Transfer Case, Drivers Side.
ECM - remove panel that is below Glove box, ECM is located just above it.
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.
1991 Chevy S-10 / T-10 Blazer 4WD Automatic
99% of the time, the Speedometer doesn't work because the VSS (Variable Speed Sensor) stops working. The VSS on a 2WD is located on the tailshaft of the transmission, drivers side. On a 4WD the VSS is located on the tailshaft of the Transfer Case, drivers side.
You will need a 1" socket to remove this sensor. All sockets come as either a 6 point or a 12 point, these are the number of angles in which to lock on to its recepticle, for this purpose a 12 point socket is prefered.
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