Speed sensor problem

More then likely it's the VSS - vehicle speed sensor .

DTC P0503
Vehicle Speed Sensor (VSS) Circuit Intermittent

Circuit Description
The vehicle speed sensor (VSS) assembly provides vehicle speed information to the powertrain control module (PCM). The VSS assembly is a permanent magnet generator. The VSS produces an AC voltage as rotor teeth on the output shaft of the transmission, 2WD, or transfer case, 4WD/AWD, pass through the sensor's magnetic field. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The PCM converts the pulsing voltage to vehicle speed. The PCM uses the vehicle speed signal to determine shift timing and torque converter clutch (TCC) scheduling.
When the PCM detects an unrealistically large drop in vehicle speed, then DTC P0503 sets. DTC P0503 is a type B DTC.

No fuse , sensor make own voltage
The vehicle speed sensor (VSS) provides vehicle speed information to the powertrain control module (PCM) or transmission control module (TCM). The VSS is a permanent magnet (PM) generator. The PM generator produces a pulsing AC voltage as rotor teeth on the transmission output shaft pass through the sensor's magnetic field. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. Output voltage varies with speed from a minimum of 0.5 volts at 100 RPM to more than 100 volts at 8,000 RPM. The PCM/TCM converts the pulsing voltage to vehicle speed. The PCM/TCM uses the vehicle speed signal to determine shift timing and TCC scheduling.
. What code # P0 what ? What speed sensor ? VSS - vehicle speed sensor , wheel speed sensor ? No diagnostic code tells you the sensor is mess up . Sensors circuit's can set a number code's lo voltage , high voltage , short to ground , open circuit . Your best bet ,take it to a qualified repair shop.

Why a generator won't produce electricity?
After the unit is running, the generator rotational speed reaches the rated speed, the AC exciter stator excitation circuit switch is closed, the voltage regulator is raised to the maximum direction, at this time, the generator has no output voltage or the voltage is very low. That's why a generator fails to produce electricity.

You might try adjusting the speed sensor. It may simply just be that they are not heavy enough to make it turn fast enough to work. The following information should help you to make the adjustment I mentioned. Speed Sensor Testing and Adjustment for Stairmaster 4400cl and 4600cl Steppers Testing and Adjustment of Stairmaster 4600CL and 4400CL Speed Sensor Tools Needed: Volt Meter, 7/16" Wrench
A common misconception about battery powered units, it that it only requires you to step on the pedals to power the console; when in fact the speed sensor plays a major role in powering the console.
If you step on the pedals and they fall to the floor due to the console not powering up so there is no resistance, you should check the speed sensor.
The speed sensor is mounted to the alternator and reads the speed sensor disc when the unit is pedaled producing an AC voltage. The voltage from the speed sensor can be tested at the connection of the speed sensor to the lower control board. The connection is a red and black wire. Using AC setting on your volt meter at its lowest range, place the red lead to the red wire and the black lead to the black wire. Make sure the leads of the volt meter are making a good connection. Now step on the unit and verify the voltage from the speed sensor. A good speed sensor will produce about 3 VAC before the console powers up.
If the voltage is not correct, inspect the adjustment of the speed sensor. It may be necessary to adjust the sensor closer to the speed sensor disc. Proper gap of the speed sensor to the disc is about the thickness of a business card.
Retest unit after making speed sensor adjustment.

follow the instruction and fix it. God bless you
When a wheel speed sensor (WSS) fails or there's a problem in the sensor's wiring circuit, it usually disables the ABS system and causes the ABS warning light to come on. Loss of a wheel speed signal is a serious problem because the ABS module needs accurate input from all its sensors to determine whether or not a wheel is locking up. Without this vital information, the ABS system can't do its thing.
Wheel speed sensors produce an alternating current (AC) output voltage that varies in frequency and amplitude with wheel speed. The faster the wheel turns, the greater the frequency and amplitude of the sensor's output signal. The strength of the signal can be affected by resistance in the sensor, resistance in the wiring and connectors, metallic debris on the end of the sensor, and the air gap between the sensor and tone ring mounted on the axle, hub, brake rotor, drum or CV joint.
A narrow air gap is usually necessary to induce a strong signal in the sensor's magnetic windings. Air gaps typically range from .016 in. to as much as .050 in. (0.40 to 1.3 mm) depending on the application. If the ABS warning light is on and you find a code for a wheel speed sensor (and the sensor is adjustable), the problem may be nothing more than too wide an air gap. Use a brass or nonmagnetic feeler gauge set the gap to the factory recommended specs.
Variations in the air gap can also cause fluctuations in the sensor's output signal. These may be caused by bad wheel bearings or missing, broken or chipped teeth on a tone ring. Even minor damage to the tone ring that's nearly impossible to see can sometimes cause a problem. One equipment supplier makes a test bench with a magnetic pickup and oscilloscope to check tone rings on remanufactured FWD axle shafts. The setup simulates the signal produced in a wheel speed sensor. Tests have shown that a variation in height of only about .010 inch on a single tooth can cause a noticeable fluctuation in the sensor's output signal!
WHEEL SPEED SENSOR CHECKS
One way to check a suspicious wheel speed sensor is to measure its output voltage. One way to do this is to plug a breakout box into the ABS module's wiring harness and attach the test leads from a digital volt ohm meter (DVOM) to the appropriate pins for the WSS circuit.
A good wheel speed sensor will generally produce an alternating current (AC) voltage reading of 50 to 700 MV when the wheel is spun by hand at about one revolution per second. Refer to a shop manual for the sensor's exact voltage specifications.
A low voltage reading or no reading calls for a direct measurement of the resistance in the WSS circuit (with the key off). This should be done through the breakout box to check the entire circuit. A good wheel speed sensor and circuit will typically have a resistance of 800 to 1400 ohms (specs vary, so refer to a manual for the exact numbers).
If the sensor circuit has too much resistance, reads open or is shorted (little or no resistance), measure the resistance across the sensor itself. If the sensor itself reads within specs, the problem is in the wiring or connectors. If not, then you have identified a bad sensor that needs to be replaced.

how about a PO133 ,,,should be the first in system

Schematic
The Oxygen Sensor 1 (O2S-1) is an electrical source that responds to oxygen content in the exhaust manifold. When the sensor reaches approximately 316°C (600°F), it produces a voltage based on the difference in oxygen between the atmosphere and exhaust gas. The PCM sends a bias voltage (391-491 mV) on the signal line which is pulled up through high resistance. When the O2S-1 is cold, it produces no voltage and has extremely high internal resistance. The internal resistance of the sensor is much greater than the resistance of the bias pull-up resistor. However, when the sensor heats up, it produces voltage that overrides the bias voltage. This voltage is read by the PCM to determine a rich/lean O2S-1 signal used to adjust injector pulse width. Under normal conditions, low sensor voltage means high oxygen content/lean air-fuel mixture and vice versa. Normal sensor readings will fluctuate between 10 mV and 999 mV DTC P0133 sets when the O2S-1 signal rich to lean or lean to rich average response time is too slow.

DTC PARAMETERS
DTC P0133 will set if the average response time of the LEAN to RICH switches is greater than 125 ms or the average response time of the RICH to LEAN switches is greater than 156 ms for 100 seconds when:
^ Engine speed is between 1500 and 3200 RPM
^ Loop status is closed
^ Calculated air flow is greater than 7 gm/s
^ Commanded air/fuel ratio is 14.7 to 1
^ No cam, CKP, ECT, EGR, EVAP purge solenoid, fuel trim, IAT, MAP misfire, system voltage or TP sensor DTCs have been set.

DTC P0133 diagnostic runs continuously once the once the above conditions have been met.

DTC P0133 is a type B DTC.

DIAGNOSTIC AIDS
Possible causes of DTC P0133:
^ An intermittent connection or corrosion in the O2S-1 harness connector can set this DTC. Use Scan tool to monitor O2S-1 voltage with engine running at normal operating temperature while wiggling the signal and ground wire. Make sure the sensor is tight.
^ The most probable cause for DTC P0133 is contamination. Check for obvious contamination (oil, fuel or engine coolant) by removing sensor. Identify and correct the cause of the contamination if contaminated. Replace the O2S-1.
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Speed Sensor Testing and Adjustment for Stairmaster 4400cl and 4600cl Steppers Testing and Adjustment of Stairmaster 4600CL and 4400CL Speed Sensor Tools Needed: Volt Meter, 7/16" Wrench
A common misconception about battery powered units, it that it only requires you to step on the pedals to power the console; when in fact the speed sensor plays a major role in powering the console.
If you step on the pedals and they fall to the floor due to the console not powering up so there is no resistance, you should check the speed sensor.
The speed sensor is mounted to the alternator and reads the speed sensor disc when the unit is pedaled producing an AC voltage. The voltage from the speed sensor can be tested at the connection of the speed sensor to the lower control board. The connection is a red and black wire. Using AC setting on your volt meter at its lowest range, place the red lead to the red wire and the black lead to the black wire. Make sure the leads of the volt meter are making a good connection. Now step on the unit and verify the voltage from the speed sensor. A good speed sensor will produce about 3 VAC before the console powers up.
If the voltage is not correct, inspect the adjustment of the speed sensor. It may be necessary to adjust the sensor closer to the speed sensor disc. Proper gap of the speed sensor to the disc is about the thickness of a business card.
Retest unit after making speed sensor adjustment.


Stairmaster Stepper Speed Sensor Testing and Adjustment 4400CL and...

If your car is a newer model there is what they call a speed sensor.The first thing I would do is to make sure that the connector is tightly snapped in place.If it is now I would then inspect the speed sensor itself.On the end of this sensor there is a small gear that sends electrical impulses that are converted by other systems in your car to produce a speed value on your speedometer.This sensor can be tested with a voltmeter.Turn the gear at the bottom of the sensor and measure the voltage .If the voltage produced doesn't reach .5 or > than you have a bad sensor.I recommend you take it to a local service station to have it tested because the voltage values are different for all cars.Also inspect the gear for damages such as broken teeth.

sounds like your vehicle speed sensor is broken. here is a tutorial from autozone.com

OPERATION


The vehicle speed sensor is made up of a coil mounted on the transmission and a tooth rotor mounted to the output shaft of the transmission. As each tooth nears the coil, the coil produces an AC voltage pulse. As the vehicle speed increases the number of voltage pulses per second increases.

TESTING


See Figure 1

1. To test the VSS, backprobe the VSS terminals with a high impedance voltmeter (set at the AC voltage scale).
2. Safely raise and support the entire vehicle using jackstands. Make absolutely sure the vehicle is stable.
3. Start the vehicle and place it in gear.
4. Verify that the VSS voltage increases as the drive shaft speed increases.
5. If the VSS voltage is not as specified the VSS may be faulty.

Fig. Fig. 1: Vehicle Speed Sensor (VSS) and vehicle speed signal buffer wiring diagram

REMOVAL & INSTALLATION


See Figure 2

1. Disconnect the negative battery cable.
2. Disengage the electrical connection.
3. Unfasten the sensor retainers.
4. Remove the sensor and gasket or O-ring.

To install:

1. Install the sensor with a new gasket or O-ring.
2. Fasten the sensor retainers.
3. Engage the electrical connections.
4. Connect the negative battery cable.

Fig. Fig. 2: Vehicle Speed Sensor (VSS) location

problem could be in the sensor wire or the pcm . the speed sensor ia a permanent magnet generator mount on transaxle.it trigger by a tooth rotor on the transaxle out put shaft. as the shaft rotate it produces a c voltage which make the speed ometer to work.check your fuse and ground wire to speedometer.and to the sensor wire.