Speed Sensor

[rasheed52479]

My car turns on but would not drive forward in D. I hooked it up to a scanner and it states P0500 speed sensor. I called up Kragen and they said there is 2, one on the right and one of the left. How do you know which one is bad? I thought there was only one sensor. I also searched the forums. I found some information but the pictures do not load because it is too old. Does anyone have any pictures of the location of the sensor on top of the transmission?

Post from Nigel back in 1994

Hey guys,

Here is some more info requested on the Speed Sensor I had replaced last month.

Vehicle Speed Sensor

DATA TROUBLE CODE: P0500

CIRCUIT DESCRIPTION

.... Please see picture 1 in the attached doc

PURPOSE

The Vehicle Speed Sensor (VSS) reports road speed to the Engine Control Module (ECM) . This information is used for the speedometer, transmission shifting, to synchronize emission systems and to adjust for various engine demands.

OPERATION

The sensor is a reed switch that is controlled by a rotating magnet. As the magnet passes under the sensor the contacts close momentarily, resulting in a ground signal. The frequency of these ground signals sent to the ECM is relevant to vehicle speed. The Vehicle Speed Sensor outputs a 4-pulse signal for every revolution of the rotor shaft, which is rotated by the transmission output shaft via the driven gear. After this signal is converted into a more precise rectangular waveform by the waveform shaping circuit inside the combination meter, it is then transmitted to the Engine Control Module. The Engine Control Module determines the vehicle speed based on the frequency of these pulse signals.

DIAGNOSTIC TROUBLE CODE P0500

No vehicle speed sensor signal to Engine Control Module (when vehicle is being driven).

TROUBLE AREA

· Open or short in vehicle speed sensor circuit.

· Vehicle Speed Sensor

· Combination meter.

· Engine Control Module.

LOCATING AND REMOVING OF THE VEHICLE SPEED SENSOR

The Vehicle Speed Sensor is attached to the outside/top of the trans axle case with one 10 mm hex head bolt. To locate use a flash light and look down between the firewall and the throttle valve assembly. The Sensor is approx 9" from the firewall and about 12" below the throttle assembly. Unplug the electrical connector, remove the hex bolt, and lift out the sensor.

Note: there are numerous sensors on this vehicle. Two of the Lexus dealer parts dept people I called, before I knew the OEM part #, could not determine the correct sensor. They finally guessed and gave me a price on the wrong part? The correct one will have a small gear on the lower end of the sensor.

INSPECTION AND TESTING OF VEHICLE SPEED SENSOR

.... Please see picture 2 in the attached doc

1. Connect the positive (+) lead from the battery to terminal 1 and negative (-) lead to terminal 2.

2. Connect the positive (+) lead from a Digital Volt Ohmmeter to terminal 3 and the negative (-) lead to terminal 2.

3. Rotate the shaft.

4. Check that there is a voltage change from approximately 0.0 volts to 11.0 volts or more between terminals 2 and 3. The voltage should change 4 times per revolution of the Vehicle Speed Sensor shaft.

5. If operation is not as specified replace the Vehicle Speed Sensor.

Electrical testing of other circuit components such as the Combination meter and ECM is also possible. However, if you need to go beyond the sensor test I have already included you’ll probably need more technical assistance. Most of us (Do It Yourself Mechanics) like myself, who have little or no Auto computer or electronic control training and no special diagnostic equipment at home are at the mercy of the dealers and other specialty auto shops. When we need a code or more than a standard multi (volt) meter we are out of our area of expertise. At that point we either pay to have someone service our car or learn to live with the irritation of having an intermittent or permanent problem and put up with the nuisance as long as the car is still drivable.

If the car is driven by our wife, paying someone may be the only option. biggrin.gif

The OEM Part No. for the Vehicle speed sensor (aka speedometer speed sensor) is 8318112040. This part from the dealer will set you back about $210.00. You may be able to buy an off brand sensor at a discount auto parts store or from a salvage yard for less.

My old man was an electronics design engineer. He was usually an optimist, but he used to say that the more electronic bells and whistles that were put on cars, the more that would eventually fail. He drove standard cars his entire life and was much happier than his friends that did not.

I hope this info helps ………Nigel

[George_Jetson]

P0500 is the vehicle speed sensor, it is driven by a gear that is attached to the differential carrier. The code indicates that the computer is not seeing the signal from this sensor. BUT you also state that the car will not drive, so I assume that you mean it will not move forward. What happens when you place the car in reverse? Does it move then?

If the car is not moving at all, then you need to look at the transmission. The ECM is generating the code because it believes that the car is in gear, and engine is running (and the RPM is responding to the throttle), but yet the ECM does not see the vehicle as moving. I would bet that there is no problem with the sensor, it is the fact that the car is not moving.

Now I might have read you post wrong, but if I am correct about the car not moving at all, you need to start looking at the transmission. Start with checking the trans oil. What is the level? Is it pink and what does it smell like?

[rasheed52479]

P0500 is the vehicle speed sensor, it is driven by a gear that is attached to the differential carrier. The code indicates that the computer is not seeing the signal from this sensor. BUT you also state that the car will not drive, so I assume that you mean it will not move forward. What happens when you place the car in reverse? Does it move then?

If the car is not moving at all, then you need to look at the transmission. The ECM is generating the code because it believes that the car is in gear, and engine is running (and the RPM is responding to the throttle), but yet the ECM does not see the vehicle as moving. I would bet that there is no problem with the sensor, it is the fact that the car is not moving.

Now I might have read you post wrong, but if I am correct about the car not moving at all, you need to start looking at the transmission. Start with checking the trans oil. What is the level? Is it pink and what does it smell like?

Thanks for the response. I will check out the tranmission oil. When I put it in reverse, it reverses. When I put it in drive, it will only move after I accelerate till 4k rpm, then it will move slowly forward.