Where is the velocity sensor - 1999 Lexus RX 300

Check the
Vehicle Speed Sensor The vehicle speed sensor (VSS) (Figure 43) is a variable reluctance or Hall-effect sensor that generates a waveform with a frequency that is proportional to the speed of the vehicle. If the vehicle is moving at a relatively low velocity, the sensor produces a signal with a low frequency. As the vehicle velocity increases, the sensor generates a signal with a higher frequency. The PCM uses the frequency signal generated by the VSS (and other inputs) to control such parameters as fuel injection, ignition control, transmission/transaxle shift scheduling and torque converter clutch scheduling. That same VSS signal is use for the tachometer as well !

Throttle position sensor could be becoming faulty. Puts out a specific millivolt to be read by computer. If reading is unstable could cause issue. How about fuel filter? Good luck.

I'm sure sure its the speed sensor on the transmission it may be just a loose connection or a bad sensor.

the vss is a variable reluctance or hall effect sensor that generates a waveform with a frequency that is proportional to the speed of the vehicle. if the vehicle is moving at a relatively low velocity , the sensor produces a signal with a low frequency. as the vehicle velocity increases,the sensor generate a signal with a higher frequency. the powertrain control module uses the frequency signal generated by the vss (and other inputs) to control such parameters as fuel injection, ignition control, transmission shifting and torgue converter clutch scheduling

E150?

Vehicle Speed Sensor The Vehicle Speed Sensor (VSS) (Figure 36) is a variable reluctance or Hall effect type sensor that generates waveform with a frequency that is proportional to the speed of the vehicle. If the vehicle is moving at a relatively low velocity, the sensor produces a signal with a low frequency. As the vehicle velocity increases, the sensor generates a signal with a higher frequency. The PCM uses the frequency signal generated by the VSS (and other inputs) to control such parameters as fuel injection, ignition timing, transmission/transaxle shift scheduling and torque converter clutch scheduling.


Typical VSS

Yours is mounted on the rear axle at the differential (pig).

wires are:

Red/Pink

LG/BK

Transmission with engine 3.0L, takes Transmission Fluid T IV
Transmission with engine i,2.3L , takes Transmission Fluid MV

The MAF Sensor (Mass Air Flow) is located in the air induction system between the air filter and the throttle body.

Be certain to inspect very well for any air or vacuum leaks in the air induction system or for any loose hose clamps or fasteners in the air induction system, especially between the MAF Sensor and the throttle body. There can be no un-metered air entering the engine or the engine performance will be effected and the check engine light, or MIL (Malfunction Indicator Light) will come on, and P0170 is only one DTC (Data Trouble Code) that un-metered air can cause.

Also, be certain to check for any obstuctions on the air velocity grid to the MAF Sensor, or in the air flow to the MAF Sensor such as a plugged up air filter, or something sucked up into the air intake for the air cleaner assembly.

The MAF Sensor can be removed from the MAF housing and cleaned using carburetor cleaner in a spray can to clean off the fine dust that often builds up on the air velocity sensor part of the MAF Sensor and causes poor performance from the MAF Sensor. (it will require a tamper resistant torx bit, and note the position that the MAF Sensor is positioned in the MAF housing so that it is installed back into the MAF housing properly)

Then clean off the MAF Sensor with the carburetor spray. (From a spray can only, and do not submerge the MAF sensor in any type of water, cleaner, or solvent, or the MAF Sensor will be damaged)

If cleaning the MAF Sensor does not solve the problem, then replace the MAF Sensor and be sure to install it with the air velocity grid facing the air filter, and be sure to tighten all the hose clamps or fasteners well.

Here are a few links to MAF Sensors for that vehicle, and an image to help assist you.



Replacement MAF- $23.27
http://www.familycar.com/store/item/Mercedes-Benz_C230_Replacement_Mass-Air-Flow-Sensor_1997_2000_RBM316703.html


Bosch MAF- $134.95
http://www.familycar.com/store/item/Mercedes-Benz_C230_Bosch_Mass-Air-Flow-Sensor_1997_2000_W0133-1599901.html


Beck Arnley MAF- $295.60
http://www.familycar.com/store/item/Mercedes-Benz_C230_Beck-Arnley_Mass-Air-Flow-Sensor_1997_2000_157-0367.html

The MAF sensor (Mass Air Flow) is located in in the air induction system usually just after the air filter and before the throttle body, and the ECM (Engine Control Module) uses the signal generated from the MAF sensor to determine how much fuel the engine receives. However, before you replace the MAF sensor you should be certain that there are no air or vacuum leaks in the air induction system especially between the throttle body and the MAF sensor, and also that all of the hose clamps are all good and tight on the air induction boot especially between the throttle body and the MAF sensor, and check if the air flow is being restricted from the air cleaner side of the MAF. (check the air filter and check the air intake to the air cleaner for any obstructions that might be restricting the air flow to the MAF)

You can also clean the MAF sensor with carburetor spray because they build up a very fine dust on the air velocity sensors that are mounted on wires that are suspended in the air stream to monitor and determine the amount of air flow into the engine, and when the MAF sensor becomes dirty the MAF sensor will loose performance. Be very careful when cleaning the air velocity sensors inside of the MAF sensor because they are very delicte and are easily damaged, and do not touch them with anything other than the spray from the carburetor can and that is all that is necessary to clean the air velocity sensors. Here are some images that I have put together to assist you.

Yes it is all related. It sound's like your speed sensor (VVS) has gone bad. There are two of them, one is an in put Velocity sensor and the out is the out put Velocity sensor.
Your going to have to get the Van scanned to find out which on has gone bad. Most of the time it's going to be the out put sensor and it not that hard to replace. 
You can do it your self or a transmission shop, as for getting your Van scanned for the codes to let you know which sensor when bad. Auto Zone or Parts source will scan for free and can give you instructions on how to locate and replace the sensor.
Good luck and hope this helps.

the flashing O/D light usually means you have a bad speed sensor that sends speed info to the engine & trans computer.

Vehicle Speed Sensor The vehicle speed sensor (VSS) (Figure 42) is a variable reluctance or Hall-effect sensor that generates a waveform with a frequency that is proportional to the speed of the vehicle. If the vehicle is moving at a relatively low velocity, the sensor produces a signal with a low frequency. As the vehicle velocity increases, the sensor generates a signal with a higher frequency. The PCM uses the frequency signal generated by the VSS (and other inputs) to control such parameters as fuel injection, ignition control, transmission/transaxle shift scheduling and torque converter clutch scheduling.
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Vehicle Speed Sensor The vehicle speed sensor (VSS) (Figure 42) is a variable reluctance or Hall-effect sensor that generates a waveform with a frequency that is proportional to the speed of the vehicle. If the vehicle is moving at a relatively low velocity, the sensor produces a signal with a low frequency. As the vehicle velocity increases, the sensor generates a signal with a higher frequency. The PCM uses the frequency signal generated by the VSS (and other inputs) to control such parameters as fuel injection, ignition control, transmission/transaxle shift scheduling and torque converter clutch scheduling.

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Some trans use an OSS, Output Shaft Sensor instead of a VSS. Depends on which trans you have, 4R100 or 4R70W

Transmission Control Switch (TCS) and Transmission Control Indicator Lamp (TCIL)
The transmission control switch (TCS) is a momentary contact switch. When the switch is pressed, a signal is sent to the powertrain control module (PCM) to allow automatic shifts from first through fourth gears or first through third gears only. The PCM energizes the transmission control indicator lamp (TCIL) when the switch is off.

The TCIL indicates overdrive cancel mode activated (lamp on) and electronic pressure control (EPC) circuit shorted (lamp flashing) or monitored sensor failure.

Output Shaft Speed (OSS) Sensor
The output shaft speed (OSS) sensor is a magnetic pickup, located at the output shaft ring gear, that sends a signal to the powertrain control module (PCM) to indicate transmission output shaft speed. The OSS is used for torque converter clutch control, shift scheduling and to determine electronic pressure control.