Where is speedomter sensor

There are three different transfer case's ! Which of these does your olds have ?

Transfer Case - NVG 136-NP4 (One Speed Automatic)
Transfer Case - NVG 233-NP1 (Two Speed Selectable)
Transfer Case - NVG 236 (Two Speed Automatic)

All three have an electronic control module ! When the light is on DTC'S are stored in the transfer case shift control module .

SERVICE indicator (AWD/4WD) lamp
The SERVICE indicator (AWD/4WD) lamp is an integral part of the instrument cluster and cannot be serviced separately. This lamp is used to inform the driver of the vehicle of malfunctions within the automatic transfer case (ATC) system. The SERVICE indicator (AWD/4WD) lamp is controlled by the transfer case shift control module via a Class 2 serial data message.

There are three speed sensors on the Automatic Transfer Case (ATC), two on the rear output shaft and one on the front output shaft. Each speed sensor is a Permanent Magnet (PM) generator. The PM generator produces a pulsing AC voltage. The AC voltage level and number of pulses increases as speed increases.
Vehicle Speed Sensor
One of the two speed sensors on the rear output shaft is the vehicle speed sensor (VSS). It is an input to the vehicle control module (VCM). The VCM sends this information to the transfer case shift control module via the Class 2 Serial Data bus.
Rear Propshaft Speed Sensor
The transfer case shift control module converts the pulsating AC voltage from the rear propshaft speed sensor to a Rear Propshaft Speed in RPMs to be used for calculations. The Rear Propshaft Speed can be displayed with a scan tool.
Front Propshaft Speed Sensor
The transfer case shift control module converts the pulsating AC voltage from the front propshaft speed sensor to Front Propshaft Speed in RPM to be used for calculations, and to monitor the difference between the front and rear propshaft sensor speed. It is also used in the AUTO 4WD mode of operation to determine the amount of slip and the percent of torque to apply to the front axle. The Front Propshaft Speed can be displayed with a scan tool.

Transfer Case Encoder Motor
The transfer case encoder motor is a permanent magnet D.C. motor and gear reduction assembly. The encoder motor is controlled with a Pulse Width Modulated (PWM) signal provided by the transfer case shift control module. It is located on the left hand side (drivers side) of the transfer case. When activated it turns the sector shaft of the transfer case to shift the transfer case. This circuit consists of a power supply relay (Motor Feed A circuit ) that supplies voltage to the motor. The Motor Control B circuit is a PWM driver that varies the duty cycle to control the amount of current through the motor to ground.

There are a number of codes that can set .
DTC C0300 Rear Speed Sensor Malfunction
DTC C0305 Front Speed Sensor Malfunction
DTC C0308 Motor A/B Circuit Low
DTC C0309 Motor A/B Circuit High
DTC C0310 Motor A/B Circuit Open
DTC C0315 Motor Ground Circuit Open
DTC C0374 General System Malfunction
DTC C0376 Front/Rear Shaft Speed Mismatch
DTC C0550 ECU Malfunction
DTC C0611 VIN Information Error

You don't want to just start replacing parts , that could cost $$$$$$ . You could check connections at all the sensors an the control module , but other then that ,well . Your best bet , take it to a qualified repair shop .

My best advice to you is to buy a repair-service manual specific to your vehicle and follow the tear-down and rebuild procedures. You can buy hard cover books online or download them too.

According to http://repairpal.com/OBD-II-Code-P0500:

Vehicle Speed Sensor Malfunction
Symptoms

• Check Engine Light will illuminate
• Vehicle may not shift properly
• Speedometer may not operate correctly
• In some cases, there are no adverse conditions noticed by the driver
• In some cases, there may be performance problems and/or shifting problems.
• Other warning lights may come on such as the ABS light and Traction Control light.

Common Problems That Trigger the P0500 Code

• Defective Vehicle Speed Sensor
• Defective Speedometer
• Vehicle Speed Sensor wiring or connector
• Communication (CAN) bus problems
• Defective transmission or differential Vehicle Speed Sensor drive gear

Common Misdiagnoses

• Speedomter problem
• Internal Transmission problem
• ABS/Traction Control probelm
• Driveline problem

04 GC
TCR?
easter egg hunt 1000
clear the code with any scan tool, if it comes back, it real
do that yet (as we do with all DTCs on all cars?)

so dash cluster showed, C140F, right?, not a real scan tool
not autozoned? scanned.?
if not fully scanned, how would you know there are 5 more DTC's
and that be very important.
why is last, tests are next unless gue$$ is the game.
and you wonder why?

MY FSM BOOK shows.
C140F-TRANSFER CASE RANGE POSITION SENSOR ERRATIC PERFORMANCE

this is pretty clear, and the steps to test it is in the same book.
quotes. (part)
The Final Drive Control Module detects excessive voltage fluctuation on the Mode Sensor Signal circuit.
quote
2. (T504) DRIVETRAIN 5 VOLT SUPPLY VOLTAGE ERRATIC
NOTE: This DTC sets when the Final Drive Control Module
detects excessive voltage fluctuation on the Mode Sensor Signal
circuit. Perform a thorough inspection of all wiring and connectors
between the sensor and the control module.
Turn the ignition off.
Disconnect the Transfer Case Motor harness connector.
Turn the ignition on.
Measure the voltage of the (T504) Drivetrain 5 Volt Supply circuit.
NOTE: Voltage should be approximately 5.0 volts and steady.
Compare any slight fluctuations found to a known good circuit in
order to verify voltmeter functionality.
Is the voltage approximately 5.0 volts and steady?
Yes >> Go to 6
No >> Go to 3
end, quote (partial)

14 checks above is 1st.
got a voltmeter
no the buy a new swtich.
checked all 4 + fuses related to this?

the plug is on the transfer case.

here it is.

The vehicle speed sensor is located in the transfer case housing. To get your speedometer working you will have to connect the wires back to the speed sensor.

Under the battery tray is a common ground point. It'll have several black wires going to a connector that is bolted to the frame. Remove this bolt, clean the area up, and bolt it back in place. If the speedometer doesn't work after this, then you probably need a vehicle speed sensor VSS.

I have gmc jimmy speedomter wront work abs light comes on will not shift we Chang the vss still disentangle help

Most cars these days have whats called a speed sensor that is electronic. And fail all the time. I would look into this first. The part itself is around $50. If you feel uncomfortable replacing it your self, take it into a shop and they can make sure its the sensor and give you a statement on the cost and repair.

Check the vehicle speed sensor at the transmission.

This DTC detects a short to voltage in the Motor Control A or Motor Control B circuits, or a shorted motor.
The transfer case motor is a bi-directional, permanent magnet, D.C. motor. When energized, (through Motor Control A or Motor Control B, the ground is provided by the opposing Motor Control circuit and then grounded through the transfer case shift control module ground circuit), the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between 4H, AUTO 4WD, 2H, N, and 4L ranges. While the transfer case motor is energized the transfer case shift control module also energizes the solenoid for the transfer case lock. The motor lock is disabled (locking action released) and free turning of the transfer case motor and sector shaft is then allowed.

Conditions for Setting the DTC
• The system will test the motor circuits by reading the voltage on each circuit.
• If the system detects a problem with the circuits, the DTC is logged.
• The transfer case shift control module senses a high voltage in the Motor Control A or Motor Control B circuits when a low voltage is expected.
Action Taken When the DTC Sets
• All shifting will be disabled.
• The SERVICE 4WD indicator will be latched on for the remainder of the current ignition cycle.
Conditions for Clearing the DTC
• The transfer case shift control module will clear the DTC if the condition for setting the DTC no longer exists.
• A history DTC will clear after 100 consecutive ignition cycles without a fault present.
• History DTCs can be cleared using a scan tool.

Schematic Reference: Transfer Case Control Schematics
1
Was the Transfer Case Diagnostic System Check performed?
--
Go to Step 2
Go to Diagnostic System Check - Transfer Case
2
Check the transfer Case shift control module for faulty power or grounds. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Was the condition found and corrected?
--
Go to Step 9
Go to Step 3
3
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With the scan tool, command the Motor A/B control ON and OFF.
Does the encoder motor turn ON and OFF?
--
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 4
4
Turn the ignition OFF.
Disconnect the four wire connector at the transfer case.
Turn the ignition ON, with the engine OFF.
Connect a DMM between the Motor Control A circuit harness connector and ground at the transfer case.
Is the voltage reading within the specified value?
0-0.2 V
Go to Step 5
Go to Step 6
5
Connect a DMM between the Motor Control B circuit harness connector and ground at the transfer case.
Is the voltage reading within the specified value?
0-0.2 V
Go to Step 8
Go to Step 7
6
Disconnect the transfer case shift control module.
Test the Motor Control A circuit harness connector for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Was the condition found and corrected?
--
Go to Step 9
Go to Step 8
7
Disconnect the transfer case shift control module.
Test the Motor Control B circuit harness connector for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Was the condition found and corrected?
--
Go to Step 9
Go to Step 8
8
Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .
Is the repair complete?
--
Go to Step 9
--
9
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?
--
Go to Step 2
System OK